| commit | abf38abec201cded6094801766d69e11a6c112b6 | [log] [tgz] |
|---|---|---|
| author | Neeraj Singh <neerajsi@microsoft.com> | Thu Mar 10 22:43:20 2022 +0000 |
| committer | Junio C Hamano <gitster@pobox.com> | Thu Mar 10 15:10:22 2022 -0800 |
| tree | f1258b40f52f600be015a365ae5e57ed3b977a33 | |
| 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>
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