Update mimalloc to v2.0.9 #4211
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In preparation for vendoring in a newer version of mimalloc, let's drop the current version of the topic. This reverts commit 8f9a61f, reversing changes made to 145a228. Signed-off-by: Johannes Schindelin <[email protected]>
The mingw-w64 GCC seems to link implicitly to libwinpthread, which does implement a pthread emulation (that is more complete than Git's). Let's keep preferring Git's. To avoid linker errors where it thinks that the `pthread_self` and the `pthread_create` symbols are defined twice, let's give our version a `win32_` prefix, just like we already do for `pthread_join()`. Signed-off-by: Johannes Schindelin <[email protected]>
We are about to vendor in `mimalloc`'s source code which we will want to include `git-compat-util.h` after defining that constant. Signed-off-by: Johannes Schindelin <[email protected]>
derrickstolee
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Jan 11, 2023
This commit imports mimalloc's source code as per v2.0.9, fetched from the tag at https://github.com/microsoft/mimalloc. The .c files are from the src/ subdirectory, and the .h files from the include/ subdirectory. We will subsequently modify the source code to accommodate building within Git's context. Since we plan on using the `mi_*()` family of functions, we skip the C++-specific source code, some POSIX compliant functions to interact with mimalloc, and the code that wants to support auto-magic overriding of the `malloc()` function (mimalloc-new-delete.h, alloc-posix.c, mimalloc-override.h, alloc-override.c, alloc-override-osx.c, alloc-override-win.c and static.c). To appease the `check-whitespace` job of Git's Continuous Integration, this commit was washed one time via `git rebase --whitespace=fix`. Signed-off-by: Johannes Schindelin <[email protected]>
We want to compile mimalloc's source code as part of Git, rather than requiring the code to be built as an external library: mimalloc uses a CMake-based build, which is not necessarily easy to integrate into the flavors of Git for Windows (which will be the main benefitting port). Signed-off-by: Johannes Schindelin <[email protected]>
By defining `USE_MIMALLOC`, Git can now be compiled with that nicely-fast and small allocator. Note that we have to disable a couple `DEVELOPER` options to build mimalloc's source code, as it makes heavy use of declarations after statements, among other things that disagree with Git's conventions. For example, the `-Wno-array-bounds` flag is needed because in `-O2` builds, trying to call `NtCurrentTeb()` (which `_mi_thread_id()` does on Windows) causes the bogus warning about a system header, likely related to https://sourceforge.net/p/mingw-w64/mailman/message/37674519/ and to https://gcc.gnu.org/bugzilla/show_bug.cgi?id=99578: C:/git-sdk-64-minimal/mingw64/include/psdk_inc/intrin-impl.h:838:1: error: array subscript 0 is outside array bounds of 'long long unsigned int[0]' [-Werror=array-bounds] 838 | __buildreadseg(__readgsqword, unsigned __int64, "gs", "q") | ^~~~~~~~~~~~~~ Also: The `mimalloc` library uses C11-style atomics, therefore we must require that standard when compiling with GCC if we want to use `mimalloc` (instead of requiring "only" C99). This is what we do in the CMake definition already, therefore this commit does not need to touch `contrib/buildsystems/`. Signed-off-by: Johannes Schindelin <[email protected]>
Thorough benchmarking with repacking a subset of linux.git (the commit history reachable from 93a6fef ([PATCH] fix the SYSCTL=n compilation, 2007-02-28), to be precise) suggest that this allocator is on par, in multi-threaded situations maybe even better than nedmalloc: `git repack -adfq` with mimalloc, 8 threads: 31.166991900 27.576763800 28.712311000 27.373859000 27.163141900 `git repack -adfq` with nedmalloc, 8 threads: 31.915032900 27.149883100 28.244933700 27.240188800 28.580849500 In a different test using GitHub Actions build agents (probably single-threaded, a core-strength of nedmalloc)): `git repack -q -d -l -A --unpack-unreachable=2.weeks.ago` with mimalloc: 943.426 978.500 939.709 959.811 954.605 `git repack -q -d -l -A --unpack-unreachable=2.weeks.ago` with nedmalloc: 995.383 952.179 943.253 963.043 980.468 While these measurements were not executed with complete scientific rigor, as no hardware was set aside specifically for these benchmarks, it shows that mimalloc and nedmalloc perform almost the same, nedmalloc with a bit higher variance and also slightly higher average (further testing suggests that nedmalloc performs worse in multi-threaded situations than in single-threaded ones). In short: mimalloc seems to be slightly better suited for our purposes than nedmalloc. Seeing that mimalloc is developed actively, while nedmalloc ceased to see any updates in eight years, let's use mimalloc on Windows instead. Signed-off-by: Johannes Schindelin <[email protected]>
This topic vendors in mimalloc v2.0.9, a fast allocator that allows Git for Windows to perform efficiently. Switch Git for Windows to using mimalloc instead of nedmalloc
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No, we're using it already since v2.38.0.
👍 I'll merge this PR tomorrow, I think, to have a snapshot with the cURL version that fixes #4194. |
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I recently upstreamed the mimalloc fixes we developed in Git for Windows, most notably the fix for running in Windows Nano Server. In the meantime, that PR was accepted and a new version was created from it (that also includes a couple of other fixes). Let's integrate the latest version.