Git for Windows has had fsyncing of object files enabled since "409cae91eb (mingw: change core.fsyncObjectFiles = 1 by default, 2017-09-04)". There have been requests to make core.fsyncObjectFiles the default everywhere, but there are concerns about its performance cost (perf results below). There's a long and gory thread here: https://lore.kernel.org/git/87a7xcw8sa.fsf@xxxxxxxxxxxxxx/t/. My change introduces the new 'core.fsyncobjectFiles = 2' setting, which batches the data-integrity FLUSH command sent to the disk across multiple loose object files added to the object database. We take advantage of the bulk-checkin hooks already in the add command and add some hooks to the update-index (which is used internally by stash). Details are in the last patch of the series. Here's a simple performance test script: #!/bin/sh git clone https://github.com/nodejs/node.git node-repo-cache git clone node-repo-cache node-repo cd node-repo git --version find . -name "*.c" -exec sh -c 'echo foo1 >> $1' -- {} \; echo "----GIT stash fsync" time git -c core.fsyncObjectFiles=true stash push find . -name "*.c" -exec sh -c 'echo foo2 >> $1' -- {} \; echo "----GIT stash fsync_defer" time git -c core.fsyncObjectFiles=2 stash push find . -name "*.c" -exec sh -c 'echo foo3 >> $1' -- {} \; echo "----GIT stash no_fsync" time git -c core.fsyncObjectFiles=false stash push cd .. rm -r -f node-repo Hardware: * Mac - Mac Mini 2018 running MacOS 11.5.1, APFS with a 1TB Apple NMVE SSD, * Linux - Ubuntu 20.04 - ext4 running on a Hyper-V VM with a fixed VHDX backed by a Samsung PM981. * Win - Windows NTFS - Same Hyper-V host as Linux. Operation | Mac | Linux | Windows ---------------- |---------|-------|---------- git fsync | 40.6 s | 7.8 s | 6.9s git fsync_defer | 6.5 s | 2.1 s | 3.8s git no_fsync | 1.7 s | 1.0 s | 2.6s The windows version of git is slightly different: https://github.com/git-for-windows/git/pull/3391. I also used a Windows-specific test script. I hope I'm CC'ing a reasonable set of people on this patch, based on the last discussion. Thanks, Neeraj Singh Windows Core File Systems. Neeraj Singh (2): object-file: use futimes rather than utime core.fsyncobjectfiles: batch disk flushes Documentation/config/core.txt | 17 ++++-- Makefile | 4 ++ builtin/add.c | 3 +- builtin/update-index.c | 3 + bulk-checkin.c | 105 +++++++++++++++++++++++++++++++--- bulk-checkin.h | 4 +- compat/mingw.c | 42 +++++++++----- compat/mingw.h | 2 + config.c | 4 +- config.mak.uname | 2 + configure.ac | 8 +++ git-compat-util.h | 7 +++ object-file.c | 23 ++------ wrapper.c | 36 ++++++++++++ write-or-die.c | 2 +- 15 files changed, 213 insertions(+), 49 deletions(-) base-commit: 225bc32a989d7a22fa6addafd4ce7dcd04675dbf Published-As: https://github.com/gitgitgadget/git/releases/tag/pr-git-1076%2Fneerajsi-msft%2Fneerajsi%2Fbulk-fsync-object-files-v1 Fetch-It-Via: git fetch https://github.com/gitgitgadget/git pr-git-1076/neerajsi-msft/neerajsi/bulk-fsync-object-files-v1 Pull-Request: https://github.com/git/git/pull/1076 -- gitgitgadget
