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author | Neeraj Singh <neerajsi@microsoft.com> | 2022-03-10 22:43:20 (GMT) |
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committer | Junio C Hamano <gitster@pobox.com> | 2022-03-10 23:10:22 (GMT) |
commit | abf38abec201cded6094801766d69e11a6c112b6 (patch) | |
tree | f1258b40f52f600be015a365ae5e57ed3b977a33 /environment.c | |
parent | 19d3f228c8df7e946278c96fb52acf1cea0f6a7a (diff) | |
download | git-abf38abec201cded6094801766d69e11a6c112b6.zip git-abf38abec201cded6094801766d69e11a6c112b6.tar.gz git-abf38abec201cded6094801766d69e11a6c112b6.tar.bz2 |
core.fsyncmethod: add writeout-only mode
This commit introduces the `core.fsyncMethod` configuration
knob, which can currently be set to `fsync` or `writeout-only`.
The new writeout-only mode attempts to tell the operating system to
flush its in-memory page cache to the storage hardware without issuing a
CACHE_FLUSH command to the storage controller.
Writeout-only fsync is significantly faster than a vanilla fsync on
common hardware, since data is written to a disk-side cache rather than
all the way to a durable medium. Later changes in this patch series will
take advantage of this primitive to implement batching of hardware
flushes.
When git_fsync is called with FSYNC_WRITEOUT_ONLY, it may fail and the
caller is expected to do an ordinary fsync as needed.
On Apple platforms, the fsync system call does not issue a CACHE_FLUSH
directive to the storage controller. This change updates fsync to do
fcntl(F_FULLFSYNC) to make fsync actually durable. We maintain parity
with existing behavior on Apple platforms by setting the default value
of the new core.fsyncMethod option.
Signed-off-by: Neeraj Singh <neerajsi@microsoft.com>
Signed-off-by: Junio C Hamano <gitster@pobox.com>
Diffstat (limited to 'environment.c')
-rw-r--r-- | environment.c | 1 |
1 files changed, 1 insertions, 0 deletions
diff --git a/environment.c b/environment.c index fd0501e..3e3620d 100644 --- a/environment.c +++ b/environment.c @@ -44,6 +44,7 @@ int zlib_compression_level = Z_BEST_SPEED; int pack_compression_level = Z_DEFAULT_COMPRESSION; int fsync_object_files; int use_fsync = -1; +enum fsync_method fsync_method = FSYNC_METHOD_DEFAULT; size_t packed_git_window_size = DEFAULT_PACKED_GIT_WINDOW_SIZE; size_t packed_git_limit = DEFAULT_PACKED_GIT_LIMIT; size_t delta_base_cache_limit = 96 * 1024 * 1024; |