diff options
author | Neeraj Singh <neerajsi@microsoft.com> | 2022-03-11 01:43:20 +0300 |
---|---|---|
committer | Junio C Hamano <gitster@pobox.com> | 2022-03-11 02:10:22 +0300 |
commit | abf38abec201cded6094801766d69e11a6c112b6 (patch) | |
tree | f1258b40f52f600be015a365ae5e57ed3b977a33 /write-or-die.c | |
parent | 19d3f228c8df7e946278c96fb52acf1cea0f6a7a (diff) |
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 'write-or-die.c')
-rw-r--r-- | write-or-die.c | 11 |
1 files changed, 7 insertions, 4 deletions
diff --git a/write-or-die.c b/write-or-die.c index a3d5784cec..9faa5f9f56 100644 --- a/write-or-die.c +++ b/write-or-die.c @@ -62,10 +62,13 @@ void fsync_or_die(int fd, const char *msg) use_fsync = git_env_bool("GIT_TEST_FSYNC", 1); if (!use_fsync) return; - while (fsync(fd) < 0) { - if (errno != EINTR) - die_errno("fsync error on '%s'", msg); - } + + if (fsync_method == FSYNC_METHOD_WRITEOUT_ONLY && + git_fsync(fd, FSYNC_WRITEOUT_ONLY) >= 0) + return; + + if (git_fsync(fd, FSYNC_HARDWARE_FLUSH) < 0) + die_errno("fsync error on '%s'", msg); } void write_or_die(int fd, const void *buf, size_t count) |