path: root/pack-objects.c
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2020-02-24pack-objects: convert oe_set_delta_ext() to use object_idJeff King
We already store an object_id internally, and now our sole caller also has one. Let's stop passing around the internal hash array, which adds a bit of type safety. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2019-12-01Merge branch 'jk/optim-in-pack-idx-conversion'Junio C Hamano
Code clean-up. * jk/optim-in-pack-idx-conversion: pack-objects: avoid pointless oe_map_new_pack() calls
2019-11-12pack-objects: avoid pointless oe_map_new_pack() callsJeff King
This patch fixes an extreme slowdown in pack-objects when you have more than 1023 packs. See below for numbers. Since 43fa44fa3b (pack-objects: move in_pack out of struct object_entry, 2018-04-14), we use a complicated system to save some per-object memory. Each object_entry structs gets a 10-bit field to store the index of the pack it's in. We map those indices into pointers using packing_data->in_pack_by_idx, which we initialize at the start of the program. If we have 2^10 or more packs, then we instead create an array of pack pointers, one per object. This is packing_data->in_pack. So far so good. But there's one other tricky case: if a new pack arrives after we've initialized in_pack_by_idx, it won't have an index yet. We solve that by calling oe_map_new_pack(), which just switches on the fly to the less-optimal in_pack mechanism, allocating the array and back-filling it for already-seen objects. But that logic kicks in even when we've switched to it already (whether because we really did see a new pack, or because we had too many packs in the first place). The result doesn't produce a wrong outcome, but it's very slow. What happens is this: - imagine you have a repo with 500k objects and 2000 packs that you want to repack. - before looking at any objects, we call prepare_in_pack_by_idx(). It starts allocating an index for each pack. On the 1024th pack, it sees there are too many, so it bails, leaving in_pack_by_idx as NULL. - while actually adding objects to the packing list, we call oe_set_in_pack(), which checks whether the pack already has an index. If it's one of the packs after the first 1023, then it doesn't have one, and we'll call oe_map_new_pack(). But there's no useful work for that function to do. We're already using in_pack, so it just uselessly walks over the complete list of objects, trying to backfill in_pack. And we end up doing this for almost 1000 packs (each of which may be triggered by more than one object). And each time it triggers, we may iterate over up to 500k objects. So in the absolute worst case, this is quadratic in the number of objects. The solution is simple: we don't need to bother checking whether the pack has an index if we've already converted to using in_pack, since by definition we're not going to use it. So we can just push the "does the pack have a valid index" check down into that half of the conditional, where we know we're going to use it. The current test in p5303 sadly doesn't notice this problem, since it maxes out at 1000 packs. If we add a new test to it at 2000 packs, it does show the improvement: Test HEAD^ HEAD ---------------------------------------------------------------------- 5303.12: repack (2000) 26.72(39.68+0.67) 15.70(28.70+0.66) -41.2% However, these many-pack test cases are rather expensive to run, so adding larger and larger numbers isn't appealing. Instead, we can show it off more easily by using GIT_TEST_FULL_IN_PACK_ARRAY, which forces us into the absolute worst case: no pack has an index, so we'll trigger oe_map_new_pack() pointlessly for every single object, making it truly quadratic. Here are the numbers (on git.git) with the included change to p5303: Test HEAD^ HEAD ---------------------------------------------------------------------- 5303.3: rev-list (1) 2.05(1.98+0.06) 2.06(1.99+0.06) +0.5% 5303.4: repack (1) 33.45(33.46+0.19) 2.75(2.73+0.22) -91.8% 5303.6: rev-list (50) 2.07(2.01+0.06) 2.06(2.01+0.05) -0.5% 5303.7: repack (50) 34.21(35.18+0.16) 3.49(4.50+0.12) -89.8% 5303.9: rev-list (1000) 2.87(2.78+0.08) 2.88(2.80+0.07) +0.3% 5303.10: repack (1000) 41.26(51.30+0.47) 10.75(20.75+0.44) -73.9% Again, those improvements aren't realistic for the 1-pack case (because in the real world, the full-array solution doesn't kick in), but it's more useful to be testing the more-complicated code path. While we're looking at this issue, we'll tweak one more thing: in oe_map_new_pack(), we call REALLOC_ARRAY(pack->in_pack). But we'd never expect to get here unless we're back-filling it for the first time, in which case it would be NULL. So let's switch that to ALLOC_ARRAY() for clarity, and add a BUG() to document the expectation. Unfortunately this code isn't well-covered in the test suite because it's inherently racy (it only kicks in if somebody else adds a new pack while we're in the middle of repacking). Signed-off-by: Jeff King <> Reviewed-by: Derrick Stolee <> Signed-off-by: Junio C Hamano <>
2019-09-06pack-objects: drop packlist index_pos optimizationJeff King
Once upon a time, the code to add an object to our packing list in pack-objects all lived in a single function. It computed the position within the hash table once, then used it to check if the object was already present, and if not, to add it. Later, in 2834bc27c1 (pack-objects: refactor the packing list, 2013-10-24), this was split into two functions: packlist_find() and packlist_alloc(). We ended up with an "index_pos" variable that gets passed through several functions to make it from one to the other. The resulting code is rather confusing to follow. The "index_pos" variable is sometimes undefined, if we don't yet have a hash table. This works out in practice because in that case packlist_alloc() won't use it at all, since it will have to create/grow the hash table. But it's hard to verify that, and it does cause gcc 9.2.1's -Wmaybe-uninitialized to complain when compiled with "-flto -O3" (rightfully, since we do pass the uninitialized value as a function parameter, even if nobody ends up using it). All of this is to save computing the hash index again when we're inserting into the hash table, which I found doesn't make a measurable difference in the program runtime (which is not surprising, since we're doing all kinds of other heavyweight things for each object). Let's just drop this index_pos variable entirely, simplifying the code (and pleasing the compiler). We might be better still refactoring this custom hash table to use one of our existing implementations (an oidmap, or a kh_oid_map). I stopped short of that here, but this would be the likely first step towards that anyway. Reported-by: Stephan Beyer <> Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2019-09-06pack-objects: use object_id in packlist_alloc()Jeff King
The only caller of packlist_alloc() already has a "struct object_id", and we immediately copy the hash they pass us into our own object_id. Let's avoid the unnecessary round-trip to a raw sha1 pointer. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2019-06-20hashmap: convert sha1hash() to oidhash()Jeff King
There are no callers left of sha1hash() that do not simply pass the "hash" member of a "struct object_id". Let's get rid of the outdated sha1-specific function and provide one that operates on the whole struct (even though the technique, taking the first few bytes of the hash, will remain the same). Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2019-06-20pack-objects: convert locate_object_entry_hash() to object_idJeff King
There are no callers of locate_object_entry_hash() that aren't just passing us the "hash" member of a "struct object_id". Let's take the whole struct, which gets us closer to removing all raw sha1 variables. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2019-06-20pack-objects: convert packlist_find() to use object_idJeff King
We take a raw hash pointer, but most of our callers have a "struct object_id" already. Let's switch to taking the full struct, which will let us continue removing uses of raw sha1 buffers. There are two callers that do need special attention: - in rebuild_existing_bitmaps(), we need to switch to nth_packed_object_oid(). This incurs an extra hash copy over pointing straight to the mmap'd sha1, but it shouldn't be measurable compared to the rest of the operation. - in can_reuse_delta() we already spent the effort to copy the sha1 into a "struct object_id", but now we just have to do so a little earlier in the function (we can't easily convert that function's callers because they may be pointing at mmap'd REF_DELTA blocks). Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2019-02-14pack-objects: drop unused parameter from oe_map_new_pack()Jeff King
Since 43fa44fa3b (pack-objects: move in_pack out of struct object_entry, 2018-04-14), we store the source pack for each object as a small index rather than as a pointer. When we see a new pack that has no allocated index, we fall back to generating an array of pointers by calling oe_map_new_pack(). Perhaps counter-intuitively, that function does not need to actually see our new index-less pack. It only allocates and populates the array with the existing packs, after which oe_set_in_pack() actually adds the new pack to the array. Let's drop the unused "struct packed_git" argument to oe_map_new_pack() to avoid confusion. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2019-02-05Merge branch 'ph/pack-objects-mutex-fix'Junio C Hamano
"git pack-objects" incorrectly used uninitialized mutex, which has been corrected. * ph/pack-objects-mutex-fix: pack-objects: merge read_lock and lock in packing_data struct pack-objects: move read mutex to packing_data struct
2019-01-28pack-objects: merge read_lock and lock in packing_data structPatrick Hogg
Rename the packing_data lock to obd_lock and upgrade it to a recursive mutex to make it suitable for current read_lock usages. Additionally remove the superfluous #ifndef NO_PTHREADS guard around mutex initialization in prepare_packing_data as the mutex functions themselves are already protected. Signed-off-by: Patrick Hogg <> Helped-by: Junio C Hamano <> Signed-off-by: Junio C Hamano <>
2019-01-28pack-objects: move read mutex to packing_data structPatrick Hogg
ac77d0c37 ("pack-objects: shrink size field in struct object_entry", 2018-04-14) added an extra usage of read_lock/read_unlock in the newly introduced oe_get_size_slow for thread safety in parallel calls to try_delta(). Unfortunately oe_get_size_slow is also used in serial code, some of which is called before the first invocation of ll_find_deltas. As such the read mutex is not guaranteed to be initialized. Resolve this by moving the read mutex to packing_data and initializing it in prepare_packing_data which is initialized in cmd_pack_objects. Signed-off-by: Patrick Hogg <> Reviewed-by: Duy Nguyen <> Signed-off-by: Junio C Hamano <>
2018-11-12pack-*.c: remove the_repository referencesNguyễn Thái Ngọc Duy
Signed-off-by: Nguyễn Thái Ngọc Duy <> Signed-off-by: Junio C Hamano <>
2018-10-30Merge branch 'js/pack-objects-mutex-init-fix'Junio C Hamano
A mutex used in "git pack-objects" were not correctly initialized and this caused "git repack" to dump core on Windows. * js/pack-objects-mutex-init-fix: pack-objects (mingw): initialize `packing_data` mutex in the correct spot pack-objects (mingw): demonstrate a segmentation fault with large deltas pack-objects: fix typo 'detla' -> 'delta'
2018-10-19pack-objects (mingw): initialize `packing_data` mutex in the correct spotJohannes Schindelin
In 9ac3f0e5b3e4 (pack-objects: fix performance issues on packing large deltas, 2018-07-22), a mutex was introduced that is used to guard the call to set the delta size. This commit even added code to initialize it, but at an incorrect spot: in `init_threaded_search()`, while the call to `oe_set_delta_size()` (and hence to `packing_data_lock()`) can happen in the call chain `check_object()` <- `get_object_details()` <- `prepare_pack()` <- `cmd_pack_objects()`, which is long before the `prepare_pack()` function calls `ll_find_deltas()` (which initializes the threaded search). Another tell-tale that the mutex was initialized in an incorrect spot is that the function to initialize it lives in builtin/, while the code that uses the mutex is defined in a libgit.a header file. Let's use a more appropriate function: `prepare_packing_data()`, which not only lives in libgit.a, but *has* to be called before the `packing_data` struct is used that contains that mutex. This fixes Signed-off-by: Johannes Schindelin <> Signed-off-by: Junio C Hamano <>
2018-09-17Merge branch 'jk/cocci'Junio C Hamano
spatch transformation to replace boolean uses of !hashcmp() to newly introduced oideq() is added, and applied, to regain performance lost due to support of multiple hash algorithms. * jk/cocci: show_dirstat: simplify same-content check read-cache: use oideq() in ce_compare functions convert hashmap comparison functions to oideq() convert "hashcmp() != 0" to "!hasheq()" convert "oidcmp() != 0" to "!oideq()" convert "hashcmp() == 0" to hasheq() convert "oidcmp() == 0" to oideq() introduce hasheq() and oideq() coccinelle: use <...> for function exclusion
2018-09-17Merge branch 'cc/delta-islands'Junio C Hamano
Lift code from GitHub to restrict delta computation so that an object that exists in one fork is not made into a delta against another object that does not appear in the same forked repository. * cc/delta-islands: pack-objects: move 'layer' into 'struct packing_data' pack-objects: move tree_depth into 'struct packing_data' t5320: tests for delta islands repack: add delta-islands support pack-objects: add delta-islands support pack-objects: refactor code into compute_layer_order() Add delta-islands.{c,h}
2018-09-17Merge branch 'jk/pack-delta-reuse-with-bitmap'Junio C Hamano
When creating a thin pack, which allows objects to be made into a delta against another object that is not in the resulting pack but is known to be present on the receiving end, the code learned to take advantage of the reachability bitmap; this allows the server to send a delta against a base beyond the "boundary" commit. * jk/pack-delta-reuse-with-bitmap: pack-objects: reuse on-disk deltas for thin "have" objects pack-bitmap: save "have" bitmap from walk t/perf: add perf tests for fetches from a bitmapped server t/perf: add infrastructure for measuring sizes t/perf: factor out percent calculations t/perf: factor boilerplate out of test_perf
2018-09-17Merge branch 'ds/multi-pack-index'Junio C Hamano
When there are too many packfiles in a repository (which is not recommended), looking up an object in these would require consulting many pack .idx files; a new mechanism to have a single file that consolidates all of these .idx files is introduced. * ds/multi-pack-index: (32 commits) pack-objects: consider packs in multi-pack-index midx: test a few commands that use get_all_packs treewide: use get_all_packs packfile: add all_packs list midx: fix bug that skips midx with alternates midx: stop reporting garbage midx: mark bad packed objects multi-pack-index: store local property multi-pack-index: provide more helpful usage info midx: clear midx on repack packfile: skip loading index if in multi-pack-index midx: prevent duplicate packfile loads midx: use midx in approximate_object_count midx: use existing midx when writing new one midx: use midx in abbreviation calculations midx: read objects from multi-pack-index config: create core.multiPackIndex setting midx: write object offsets midx: write object id fanout chunk midx: write object ids in a chunk ...
2018-08-29convert "hashcmp() == 0" to hasheq()Jeff King
This is the partner patch to the previous one, but covering the "hash" variants instead of "oid". Note that our coccinelle rule is slightly more complex to avoid triggering the call in hasheq(). I didn't bother to add a new rule to convert: - hasheq(E1->hash, E2->hash) + oideq(E1, E2) Since these are new functions, there won't be any such existing callers. And since most of the code is already using oideq, we're not likely to introduce new ones. We might still see "!hashcmp(E1->hash, E2->hash)" from topics in flight. But because our new rule comes after the existing ones, that should first get converted to "!oidcmp(E1, E2)" and then to "oideq(E1, E2)". Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2018-08-22Merge branch 'nd/pack-deltify-regression-fix'Junio C Hamano
In a recent update in 2.18 era, "git pack-objects" started producing a larger than necessary packfiles by missing opportunities to use large deltas. * nd/pack-deltify-regression-fix: pack-objects: fix performance issues on packing large deltas
2018-08-21pack-objects: reuse on-disk deltas for thin "have" objectsJeff King
When we serve a fetch, we pass the "wants" and "haves" from the fetch negotiation to pack-objects. That tells us not only which objects we need to send, but we also use the boundary commits as "preferred bases": their trees and blobs are candidates for delta bases, both for reusing on-disk deltas and for finding new ones. However, this misses some opportunities. Modulo some special cases like shallow or partial clones, we know that every object reachable from the "haves" could be a preferred base. We don't use all of them for two reasons: 1. It's expensive to traverse the whole history and enumerate all of the objects the other side has. 2. The delta search is expensive, so we want to keep the number of candidate bases sane. The boundary commits are the most likely to work. When we have reachability bitmaps, though, reason 1 no longer applies. We can efficiently compute the set of reachable objects on the other side (and in fact already did so as part of the bitmap set-difference to get the list of interesting objects). And using this set conveniently covers the shallow and partial cases, since we have to disable the use of bitmaps for those anyway. The second reason argues against using these bases in the search for new deltas. But there's one case where we can use this information for free: when we have an existing on-disk delta that we're considering reusing, we can do so if we know the other side has the base object. This in fact saves time during the delta search, because it's one less delta we have to compute. And that's exactly what this patch does: when we're considering whether to reuse an on-disk delta, if bitmaps tell us the other side has the object (and we're making a thin-pack), then we reuse it. Here are the results on p5311 using linux.git, which simulates a client fetching after `N` days since their last fetch: Test origin HEAD -------------------------------------------------------------------------- 5311.3: server (1 days) 0.27(0.27+0.04) 0.12(0.09+0.03) -55.6% 5311.4: size (1 days) 0.9M 237.0K -73.7% 5311.5: client (1 days) 0.04(0.05+0.00) 0.10(0.10+0.00) +150.0% 5311.7: server (2 days) 0.34(0.42+0.04) 0.13(0.10+0.03) -61.8% 5311.8: size (2 days) 1.5M 347.7K -76.5% 5311.9: client (2 days) 0.07(0.08+0.00) 0.16(0.15+0.01) +128.6% 5311.11: server (4 days) 0.56(0.77+0.08) 0.13(0.10+0.02) -76.8% 5311.12: size (4 days) 2.8M 566.6K -79.8% 5311.13: client (4 days) 0.13(0.15+0.00) 0.34(0.31+0.02) +161.5% 5311.15: server (8 days) 0.97(1.39+0.11) 0.30(0.25+0.05) -69.1% 5311.16: size (8 days) 4.3M 1.0M -76.0% 5311.17: client (8 days) 0.20(0.22+0.01) 0.53(0.52+0.01) +165.0% 5311.19: server (16 days) 1.52(2.51+0.12) 0.30(0.26+0.03) -80.3% 5311.20: size (16 days) 8.0M 2.0M -74.5% 5311.21: client (16 days) 0.40(0.47+0.03) 1.01(0.98+0.04) +152.5% 5311.23: server (32 days) 2.40(4.44+0.20) 0.31(0.26+0.04) -87.1% 5311.24: size (32 days) 14.1M 4.1M -70.9% 5311.25: client (32 days) 0.70(0.90+0.03) 1.81(1.75+0.06) +158.6% 5311.27: server (64 days) 11.76(26.57+0.29) 0.55(0.50+0.08) -95.3% 5311.28: size (64 days) 89.4M 47.4M -47.0% 5311.29: client (64 days) 5.71(9.31+0.27) 15.20(15.20+0.32) +166.2% 5311.31: server (128 days) 16.15(36.87+0.40) 0.91(0.82+0.14) -94.4% 5311.32: size (128 days) 134.8M 100.4M -25.5% 5311.33: client (128 days) 9.42(16.86+0.49) 25.34(25.80+0.46) +169.0% In all cases we save CPU time on the server (sometimes significant) and the resulting pack is smaller. We do spend more CPU time on the client side, because it has to reconstruct more deltas. But that's the right tradeoff to make, since clients tend to outnumber servers. It just means the thin pack mechanism is doing its job. From the user's perspective, the end-to-end time of the operation will generally be faster. E.g., in the 128-day case, we saved 15s on the server at a cost of 16s on the client. Since the resulting pack is 34MB smaller, this is a net win if the network speed is less than 270Mbit/s. And that's actually the worst case. The 64-day case saves just over 11s at a cost of just under 11s. So it's a slight win at any network speed, and the 40MB saved is pure bonus. That trend continues for the smaller fetches. The implementation itself is mostly straightforward, with the new logic going into check_object(). But there are two tricky bits. The first is that check_object() needs access to the relevant information (the thin flag and bitmap result). We can do this by pushing these into program-lifetime globals. The second is that the rest of the code assumes that any reused delta will point to another "struct object_entry" as its base. But of course the case we are interested in here is the one where don't have such an entry! I looked at a number of options that didn't quite work: - we could use a flag to signal a reused delta, but it's not a single bit. We have to actually store the oid of the base, which is normally done by pointing to the existing object_entry. And we'd have to modify all the code which looks at deltas. - we could add the reused bases to the end of the existing object_entry array. While this does create some extra work as later stages consider the extra entries, it's actually not too bad (we're not sending them, so they don't cost much in the delta search, and at most we'd have 2*N of them). But there's a more subtle problem. Adding to the existing array means we might need to grow it with realloc, which could move the earlier entries around. While many of the references to other entries are done by integer index, some (including ones on the stack) use pointers, which would become invalidated. This isn't insurmountable, but it would require quite a bit of refactoring (and it's hard to know that you've got it all, since it may work _most_ of the time and then fail subtly based on memory allocation patterns). - we could allocate a new one-off entry for the base. In fact, this is what an earlier version of this patch did. However, since the refactoring brought in by ad635e82d6 (Merge branch 'nd/pack-objects-pack-struct', 2018-05-23), the delta_idx code requires that both entries be in the main packing list. So taking all of those options into account, what I ended up with is a separate list of "external bases" that are not part of the main packing list. Each delta entry that points to an external base has a single-bit flag to do so; we have a little breathing room in the bitfield section of object_entry. This lets us limit the change primarily to the oe_delta() and oe_set_delta_ext() functions. And as a bonus, most of the rest of the code does not consider these dummy entries at all, saving both runtime CPU and code complexity. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2018-08-20treewide: use get_all_packsDerrick Stolee
There are many places in the codebase that want to iterate over all packfiles known to Git. The purposes are wide-ranging, and those that can take advantage of the multi-pack-index already do. So, use get_all_packs() instead of get_packed_git() to be sure we are iterating over all packfiles. Signed-off-by: Derrick Stolee <> Signed-off-by: Junio C Hamano <>
2018-08-16pack-objects: move 'layer' into 'struct packing_data'Christian Couder
This reduces the size of 'struct object_entry' from 88 bytes to 80 and therefore makes packing objects more efficient. For example on a Linux repo with 12M objects, `git pack-objects --all` needs extra 96MB memory even if the layer feature is not used. Helped-by: Jeff King <> Helped-by: Duy Nguyen <> Signed-off-by: Christian Couder <> Signed-off-by: Junio C Hamano <>
2018-08-16pack-objects: move tree_depth into 'struct packing_data'Christian Couder
This reduces the size of 'struct object_entry' and therefore makes packing objects more efficient. This also renames cmp_tree_depth() into tree_depth_compare(), as it is more modern to have the name of the compare functions end with "compare". Helped-by: Jeff King <> Helped-by: Duy Nguyen <> Signed-off-by: Christian Couder <> Signed-off-by: Junio C Hamano <>
2018-07-23pack-objects: fix performance issues on packing large deltasNguyễn Thái Ngọc Duy
Let's start with some background about oe_delta_size() and oe_set_delta_size(). If you already know, skip the next paragraph. These two are added in 0aca34e826 (pack-objects: shrink delta_size field in struct object_entry - 2018-04-14) to help reduce 'struct object_entry' size. The delta size field in this struct is reduced to only contain max 1MB. So if any new delta is produced and larger than 1MB, it's dropped because we can't really save such a large size anywhere. Fallback is provided in case existing packfiles already have large deltas, then we can retrieve it from the pack. While this should help small machines repacking large repos without large deltas (i.e. less memory pressure), dropping large deltas during the delta selection process could end up with worse pack files. And if existing packfiles already have >1MB delta and pack-objects is instructed to not reuse deltas, all of them will be dropped on the floor, and the resulting pack would be definitely bigger. There is also a regression in terms of CPU/IO if we have large on-disk deltas because fallback code needs to parse the pack every time the delta size is needed and just access to the mmap'd pack data is enough for extra page faults when memory is under pressure. Both of these issues were reported on the mailing list. Here's some numbers for comparison. Version Pack (MB) MaxRSS(kB) Time (s) ------- --------- ---------- -------- 2.17.0 5498 43513628 2494.85 2.18.0 10531 40449596 4168.94 This patch provides a better fallback that is - cheaper in terms of cpu and io because we won't have to read existing pack files as much - better in terms of pack size because the pack heuristics is back to 2.17.0 time, we do not drop large deltas at all If we encounter any delta (on-disk or created during try_delta phase) that is larger than the 1MB limit, we stop using delta_size_ field for this because it can't contain such size anyway. A new array of delta size is dynamically allocated and can hold all the deltas that 2.17.0 can. This array only contains delta sizes that delta_size_ can't contain. With this, we do not have to drop deltas in try_delta() anymore. Of course the downside is we use slightly more memory, even compared to 2.17.0. But since this is considered an uncommon case, a bit more memory consumption should not be a problem. Delta size limit is also raised from 1MB to 16MB to better cover common case and avoid that extra memory consumption (99.999% deltas in this reported repo are under 12MB; Jeff noted binary artifacts topped out at about 3MB in some other private repos). Other fields are shuffled around to keep this struct packed tight. We don't use more memory in common case even with this limit update. A note about thread synchronization. Since this code can be run in parallel during delta searching phase, we need a mutex. The realloc part in packlist_alloc() is not protected because it only happens during the object counting phase, which is always single-threaded. Access to e->delta_size_ (and by extension pack->delta_size[e - pack->objects]) is unprotected as before, the thread scheduler in pack-objects must make sure "e" is never updated by two different threads. The area under the new lock is as small as possible, avoiding locking at all in common case, since lock contention with high thread count could be expensive (most blobs are small enough that delta compute time is short and we end up taking the lock very often). The previous attempt to always hold a lock in oe_delta_size() and oe_set_delta_size() increases execution time by 33% when repacking linux.git with with 40 threads. Reported-by: Elijah Newren <> Helped-by: Elijah Newren <> Helped-by: Jeff King <> Signed-off-by: Nguyễn Thái Ngọc Duy <> Signed-off-by: Junio C Hamano <>
2018-05-30Merge branch 'js/use-bug-macro'Junio C Hamano
Developer support update, by using BUG() macro instead of die() to mark codepaths that should not happen more clearly. * js/use-bug-macro: BUG_exit_code: fix sparse "symbol not declared" warning Convert remaining die*(BUG) messages Replace all die("BUG: ...") calls by BUG() ones run-command: use BUG() to report bugs, not die() test-tool: help verifying BUG() code paths
2018-05-06Replace all die("BUG: ...") calls by BUG() onesJohannes Schindelin
In d8193743e08 (usage.c: add BUG() function, 2017-05-12), a new macro was introduced to use for reporting bugs instead of die(). It was then subsequently used to convert one single caller in 588a538ae55 (setup_git_env: convert die("BUG") to BUG(), 2017-05-12). The cover letter of the patch series containing this patch (cf is not terribly clear why only one call site was converted, or what the plan is for other, similar calls to die() to report bugs. Let's just convert all remaining ones in one fell swoop. This trick was performed by this invocation: sed -i 's/die("BUG: /BUG("/g' $(git grep -l 'die("BUG' \*.c) Signed-off-by: Johannes Schindelin <> Signed-off-by: Junio C Hamano <>
2018-04-16pack-objects: shrink size field in struct object_entryNguyễn Thái Ngọc Duy
It's very very rare that an uncompressed object is larger than 4GB (partly because Git does not handle those large files very well to begin with). Let's optimize it for the common case where object size is smaller than this limit. Shrink size field down to 31 bits and one overflow bit. If the size is too large, we read it back from disk. As noted in the previous patch, we need to return the delta size instead of canonical size when the to-be-reused object entry type is a delta instead of a canonical one. Add two compare helpers that can take advantage of the overflow bit (e.g. if the file is 4GB+, chances are it's already larger than core.bigFileThreshold and there's no point in comparing the actual value). Another note about oe_get_size_slow(). This function MUST be thread safe because SIZE() macro is used inside try_delta() which may run in parallel. Outside parallel code, no-contention locking should be dirt cheap (or insignificant compared to i/o access anyway). To exercise this code, it's best to run the test suite with something like make test GIT_TEST_OE_SIZE=4 which forces this code on all objects larger than 3 bytes. Signed-off-by: Nguyễn Thái Ngọc Duy <> Signed-off-by: Junio C Hamano <>
2018-04-16pack-objects: move in_pack out of struct object_entryNguyễn Thái Ngọc Duy
Instead of using 8 bytes (on 64 bit arch) to store a pointer to a pack. Use an index instead since the number of packs should be relatively small. This limits the number of packs we can handle to 1k. Since we can't be sure people can never run into the situation where they have more than 1k pack files. Provide a fall back route for it. If we find out they have too many packs, the new in_pack_by_idx[] array (which has at most 1k elements) will not be used. Instead we allocate in_pack[] array that holds nr_objects elements. This is similar to how the optional in_pack_pos field is handled. The new simple test is just to make sure the too-many-packs code path is at least executed. The true test is running make test GIT_TEST_FULL_IN_PACK_ARRAY=1 to take advantage of other special case tests. Signed-off-by: Nguyễn Thái Ngọc Duy <> Signed-off-by: Junio C Hamano <>
2017-05-08pack: convert struct pack_idx_entry to struct object_idbrian m. carlson
Convert struct pack_idx_entry to use struct object_id by changing the definition and applying the following semantic patch, plus the standard object_id transforms: @@ struct pack_idx_entry E1; @@ - E1.sha1 + E1.oid.hash @@ struct pack_idx_entry *E1; @@ - E1->sha1 + E1->oid.hash Signed-off-by: brian m. carlson <> Signed-off-by: Junio C Hamano <>
2014-09-18use REALLOC_ARRAY for changing the allocation size of arraysRené Scharfe
Signed-off-by: Rene Scharfe <> Signed-off-by: Junio C Hamano <>
2014-07-07hashmap: factor out getting a hash code from a SHA1Karsten Blees
Copying the first bytes of a SHA1 is duplicated in six places, however, the implications (the actual value would depend on the endianness of the platform) is documented only once. Add a properly documented API for this. Signed-off-by: Karsten Blees <> Signed-off-by: Junio C Hamano <>
2014-06-02pack-objects: use free()+xcalloc() instead of xrealloc()+memset()René Scharfe
Whenever the hash table becomes too small then its size is increased, the original part (and the added space) is zerod out using memset(), and the table is rebuilt from scratch. Simplify this proceess by returning the old memory using free() and allocating the new buffer using xcalloc(), which already clears the buffer for us. That way we avoid copying the old hash table contents needlessly inside xrealloc(). While at it, use the first array member with sizeof instead of a specific type. The old code used uint32_t and int, while index is actually an array of int32_t. Their sizes are the same basically everywhere, so it's not actually a problem, but the new code is cleaner and doesn't have to be touched should the type be changed. Signed-off-by: Rene Scharfe <> Signed-off-by: Junio C Hamano <>
2013-10-24pack-objects: refactor the packing listVicent Marti
The hash table that stores the packing list for a given `pack-objects` run was tightly coupled to the pack-objects code. In this commit, we refactor the hash table and the underlying storage array into a `packing_data` struct. The functionality for accessing and adding entries to the packing list is hence accessible from other parts of Git besides the `pack-objects` builtin. This refactoring is a requirement for further patches in this series that will require accessing the commit packing list from outside of `pack-objects`. The hash table implementation has been minimally altered: we now use table sizes which are always a power of two, to ensure a uniform index distribution in the array. Signed-off-by: Vicent Marti <> Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2006-08-04Make git-pack-objects a builtinMatthias Kestenholz
Signed-off-by: Matthias Kestenholz <> Signed-off-by: Junio C Hamano <>
2006-07-24pack-objects: check pack.window for default window sizeJeff King
For some repositories, deltas simply don't make sense. One can disable them for git-repack by adding --window, but git-push insists on making the deltas which can be very CPU-intensive for little benefit. Signed-off-by: Jeff King <> Signed-off-by: Junio C Hamano <>
2006-07-10Fix more typos, primarily in the codePavel Roskin
The only visible change is that git-blame doesn't understand "--compability" anymore, but it does accept "--compatibility" instead, which is already documented. Signed-off-by: Pavel Roskin <> Signed-off-by: Junio C Hamano <>
2006-07-01don't load objects needlessly when repackingNicolas Pitre
If no delta is attempted on some objects then it is useless to load them in memory, neither create any delta index for them. The best thing to do is therefore to load and index them only when really needed. Signed-off-by: Nicolas Pitre <> Signed-off-by: Junio C Hamano <>
2006-06-30consider previous pack undeltified object state only when reusing delta dataNicolas Pitre
Without this there would never be a chance to improve packing for previously undeltified objects. Signed-off-by: Nicolas Pitre <> Signed-off-by: Junio C Hamano <>
2006-06-29Do not try futile object pairs when repacking.Linus Torvalds
In the repacking window, if both objects we are looking at already came from the same (old) pack-file, don't bother delta'ing them against each other. That means that we'll still always check for better deltas for (and against!) _unpacked_ objects, but assuming incremental repacks, you'll avoid the delta creation 99% of the time. Signed-off-by: Linus Torvalds <> Signed-off-by: Junio C Hamano <>
2006-06-21Merge branch 'ff/c99' into nextJunio C Hamano
* ff/c99: Remove all void-pointer arithmetic.
2006-06-21upload-pack: prepare for sideband message support.Junio C Hamano
This does not implement sideband for propagating the status to the downloader yet, but add code to capture the standard error output from the pack-objects process in preparation for sending it off to the client when the protocol extension allows us to do so. Signed-off-by: Junio C Hamano <>
2006-06-20Remove all void-pointer arithmetic.Florian Forster
ANSI C99 doesn't allow void-pointer arithmetic. This patch fixes this in various ways. Usually the strategy that required the least changes was used. Signed-off-by: Florian Forster <> Signed-off-by: Junio C Hamano <>
2006-06-06pack-objects: improve path grouping heuristics.Linus Torvalds
This trivial patch not only simplifies the name hashing, it actually improves packing for both git and the kernel. The git archive pack shrinks from 6824090->6622627 bytes (a 3% improvement), and the kernel pack shrinks from 108756213 to 108219021 (a mere 0.5% improvement, but still, it's an improvement from making the hashing much simpler!) We just create a 32-bit hash, where we "age" previous characters by two bits, so the last characters in a filename count most. So when we then compare the hashes in the sort routine, filenames that end the same way sort the same way. It takes the subdirectory into account (unless the filename is > 16 characters), but files with the same name within the same subdirectory will obviously sort closer than files in different subdirectories. And, incidentally (which is why I tried the hash change in the first place, of course) builtin-rev-list.c will sort fairly close to rev-list.c. And no, it's not a "good hash" in the sense of being secure or unique, but that's not what we're looking for. The whole "hash" thing is misnamed here. It's not so much a hash as a "sorting number". [jc: rolled in simplification for computing the sorting number computation for thin pack base objects] Signed-off-by: Linus Torvalds <> Signed-off-by: Junio C Hamano <>
2006-05-31tree_entry(): new tree-walking helper functionLinus Torvalds
This adds a "tree_entry()" function that combines the common operation of doing a "tree_entry_extract()" + "update_tree_entry()". It also has a simplified calling convention, designed for simple loops that traverse over a whole tree: the arguments are pointers to the tree descriptor and a name_entry structure to fill in, and it returns a boolean "true" if there was an entry left to be gotten in the tree. This allows tree traversal with struct tree_desc desc; struct name_entry entry; desc.buf = tree->buffer; desc.size = tree->size; while (tree_entry(&desc, &entry) { ... use "entry.{path, sha1, mode, pathlen}" ... } which is not only shorter than writing it out in full, it's hopefully less error prone too. [ It's actually a tad faster too - we don't need to recalculate the entry pathlength in both extract and update, but need to do it only once. Also, some callers can avoid doing a "strlen()" on the result, since it's returned as part of the name_entry structure. However, by now we're talking just 1% speedup on "git-rev-list --objects --all", and we're definitely at the point where tree walking is no longer the issue any more. ] NOTE! Not everybody wants to use this new helper function, since some of the tree walkers very much on purpose do the descriptor update separately from the entry extraction. So the "extract + update" sequence still remains as the core sequence, this is just a simplified interface. We should probably add a silly two-line inline helper function for initializing the descriptor from the "struct tree" too, just to cut down on the noise from that common "desc" initializer. Signed-off-by: Linus Torvalds <> Signed-off-by: Junio C Hamano <>
2006-05-17Merge branch 'np/pack'Junio C Hamano
* np/pack: improve depth heuristic for maximum delta size pack-object: slightly more efficient simple euristic for further free packing improvements
2006-05-16improve depth heuristic for maximum delta sizeNicolas Pitre
This provides a linear decrement on the penalty related to delta depth instead of being an 1/x function. With this another 5% reduction is observed on packs for both the GIT repo and the Linux kernel repo, as well as fixing a pack size regression in another sample repo I have. Signed-off-by: Nicolas Pitre <> Signed-off-by: Junio C Hamano <>
2006-05-15Merge branch 'fix'Junio C Hamano
* fix: Fix pack-index issue on 64-bit platforms a bit more portably. Install git-send-email by default Fix compilation on newer NetBSD systems git config syntax updates Another config file parsing fix. checkout: use --aggressive when running a 3-way merge (-m).
2006-05-15Fix pack-index issue on 64-bit platforms a bit more portably.v1.3.3Junio C Hamano
Apparently <stdint.h> is not enough for uint32_t on OpenBSD; use "unsigned int" -- hopefully that would stay 32-bit on every platform we care about, at least until we update the pack-index file format. Our sha1 routines optimized for architectures use uint32_t and expects '#include <stdint.h>' to be enough, so OpenBSD on arm or ppc might have similar issues down the road, I dunno. Signed-off-by: Junio C Hamano <>