Re: [PATCH v5 7/7] fsmonitor: add a performance test

> Add a test utility (test-drop-caches) that enables dropping the file
> system cache on Windows.
> 
> Add a perf test (p7519-fsmonitor.sh) for fsmonitor.
> 
> Signed-off-by: Ben Peart <benpeart@microsoft.com>
> Signed-off-by: Ævar Arnfjörð Bjarmason <avarab@gmail.com>
> ---
>   Makefile                    |   1 +
>   t/helper/test-drop-caches.c | 107 +++++++++++++++++++++++++++++
>   t/perf/p7519-fsmonitor.sh   | 161 ++++++++++++++++++++++++++++++++++++++++++++
>   3 files changed, 269 insertions(+)
>   create mode 100644 t/helper/test-drop-caches.c
>   create mode 100755 t/perf/p7519-fsmonitor.sh
> 
> diff --git a/Makefile b/Makefile
> index 992dd58801..893947839f 100644
> --- a/Makefile
> +++ b/Makefile
> @@ -648,6 +648,7 @@ TEST_PROGRAMS_NEED_X += test-subprocess
>   TEST_PROGRAMS_NEED_X += test-svn-fe
>   TEST_PROGRAMS_NEED_X += test-urlmatch-normalization
>   TEST_PROGRAMS_NEED_X += test-wildmatch
> +TEST_PROGRAMS_NEED_X += test-drop-caches
>   
>   TEST_PROGRAMS = $(patsubst %,t/helper/%$X,$(TEST_PROGRAMS_NEED_X))
>   
> diff --git a/t/helper/test-drop-caches.c b/t/helper/test-drop-caches.c
> new file mode 100644
> index 0000000000..80830d920b
> --- /dev/null
> +++ b/t/helper/test-drop-caches.c
> @@ -0,0 +1,107 @@
> +#include "git-compat-util.h"
> +#include <stdio.h>
> +
> +typedef DWORD NTSTATUS;
> +
> +#ifdef GIT_WINDOWS_NATIVE
> +#include <tchar.h>
> +
> +#define STATUS_SUCCESS			(0x00000000L)
> +#define STATUS_PRIVILEGE_NOT_HELD	(0xC0000061L)
> +
> +typedef enum _SYSTEM_INFORMATION_CLASS {
> +	SystemMemoryListInformation = 80, // 80, q: SYSTEM_MEMORY_LIST_INFORMATION; s: SYSTEM_MEMORY_LIST_COMMAND (requires SeProfileSingleProcessPrivilege)
> +} SYSTEM_INFORMATION_CLASS;
> +
> +// private
> +typedef enum _SYSTEM_MEMORY_LIST_COMMAND
> +{
> +	MemoryCaptureAccessedBits,
> +	MemoryCaptureAndResetAccessedBits,
> +	MemoryEmptyWorkingSets,
> +	MemoryFlushModifiedList,
> +	MemoryPurgeStandbyList,
> +	MemoryPurgeLowPriorityStandbyList,
> +	MemoryCommandMax
> +} SYSTEM_MEMORY_LIST_COMMAND;
> +
> +BOOL GetPrivilege(HANDLE TokenHandle, LPCSTR lpName, int flags)
> +{
> +	BOOL bResult;
> +	DWORD dwBufferLength;
> +	LUID luid;
> +	TOKEN_PRIVILEGES tpPreviousState;
> +	TOKEN_PRIVILEGES tpNewState;
> +
> +	dwBufferLength = 16;
> +	bResult = LookupPrivilegeValueA(0, lpName, &luid);
> +	if (bResult)
> +	{
> +		tpNewState.PrivilegeCount = 1;
> +		tpNewState.Privileges[0].Luid = luid;
> +		tpNewState.Privileges[0].Attributes = 0;
> +		bResult = AdjustTokenPrivileges(TokenHandle, 0, &tpNewState, (DWORD)((LPBYTE)&(tpNewState.Privileges[1]) - (LPBYTE)&tpNewState), &tpPreviousState, &dwBufferLength);
> +		if (bResult)
> +		{
> +			tpPreviousState.PrivilegeCount = 1;
> +			tpPreviousState.Privileges[0].Luid = luid;
> +			tpPreviousState.Privileges[0].Attributes = flags != 0 ? 2 : 0;
> +			bResult = AdjustTokenPrivileges(TokenHandle, 0, &tpPreviousState, dwBufferLength, 0, 0);
> +		}
> +	}
> +	return bResult;
> +}
> +#endif
> +
> +int cmd_main(int argc, const char **argv)
> +{
> +	NTSTATUS status = 1;
> +#ifdef GIT_WINDOWS_NATIVE
> +	HANDLE hProcess = GetCurrentProcess();
> +	HANDLE hToken;
> +	if (!OpenProcessToken(hProcess, TOKEN_QUERY | TOKEN_ADJUST_PRIVILEGES, &hToken))
> +	{
> +		_ftprintf(stderr, _T("Can't open current process token\n"));
> +		return 1;
> +	}
> +
> +	if (!GetPrivilege(hToken, "SeProfileSingleProcessPrivilege", 1))
> +	{
> +		_ftprintf(stderr, _T("Can't get SeProfileSingleProcessPrivilege\n"));
> +		return 1;
> +	}
> +
> +	CloseHandle(hToken);
> +
> +	HMODULE ntdll = LoadLibrary(_T("ntdll.dll"));
> +	if (!ntdll)
> +	{
> +		_ftprintf(stderr, _T("Can't load ntdll.dll, wrong Windows version?\n"));
> +		return 1;
> +	}
> +
> +	NTSTATUS(WINAPI *NtSetSystemInformation)(INT, PVOID, ULONG) = (NTSTATUS(WINAPI *)(INT, PVOID, ULONG))GetProcAddress(ntdll, "NtSetSystemInformation");
> +	if (!NtSetSystemInformation)
> +	{
> +		_ftprintf(stderr, _T("Can't get function addresses, wrong Windows version?\n"));
> +		return 1;
> +	}
> +
> +	SYSTEM_MEMORY_LIST_COMMAND command = MemoryPurgeStandbyList;
> +	status = NtSetSystemInformation(
> +		SystemMemoryListInformation,
> +		&command,
> +		sizeof(SYSTEM_MEMORY_LIST_COMMAND)
> +	);
> +	if (status == STATUS_PRIVILEGE_NOT_HELD)
> +	{
> +		_ftprintf(stderr, _T("Insufficient privileges to execute the memory list command"));
> +	}
> +	else if (status != STATUS_SUCCESS)
> +	{
> +		_ftprintf(stderr, _T("Unable to execute the memory list command %lX"), status);
> +	}
> +#endif
> +
> +	return status;
> +}
> diff --git a/t/perf/p7519-fsmonitor.sh b/t/perf/p7519-fsmonitor.sh
> new file mode 100755
> index 0000000000..e41905cb9b
> --- /dev/null
> +++ b/t/perf/p7519-fsmonitor.sh
> @@ -0,0 +1,161 @@
> +#!/bin/sh
> +
> +test_description="Test core.fsmonitor"
> +
> +. ./perf-lib.sh
> +
> +# This has to be run with GIT_PERF_REPEAT_COUNT=1 to generate valid results.
> +# Otherwise the caching that happens for the nth run will negate the validity
> +# of the comparisons.
> +if [ "$GIT_PERF_REPEAT_COUNT" -ne 1 ]
> +then
> +	echo "warning: This test must be run with GIT_PERF_REPEAT_COUNT=1 to generate valid results." >&2
> +	echo "warning: Setting GIT_PERF_REPEAT_COUNT=1" >&2
> +	GIT_PERF_REPEAT_COUNT=1
> +fi
> +
> +test_perf_large_repo
> +test_checkout_worktree
> +
> +# Convert unix style paths to what Watchman expects
> +case "$(uname -s)" in
> +MINGW*|MSYS_NT*)
> +  GIT_WORK_TREE="$(cygpath -aw "$PWD" | sed 's,\\,/,g')"
> +  ;;
> +*)
> +  GIT_WORK_TREE="$PWD"
> +  ;;
> +esac
> +
> +# The big win for using fsmonitor is the elimination of the need to scan
> +# the working directory looking for changed files and untracked files. If
> +# the file information is all cached in RAM, the benefits are reduced.
> +
> +flush_disk_cache () {
> +	case "$(uname -s)" in
> +	MINGW*|MSYS_NT*)
> +	  sync && test-drop-caches
> +	  ;;
> +	*)
> +	  sudo sync && echo 3 | sudo tee /proc/sys/vm/drop_caches
> +	  ;;
> +	esac
> +
> +}
> +
> +test_lazy_prereq UNTRACKED_CACHE '
> +	{ git update-index --test-untracked-cache; ret=$?; } &&
> +	test $ret -ne 1
> +'
> +
> +test_expect_success "setup" '
> +	# Maybe set untrackedCache & splitIndex depending on the environment
> +	if test -n "$GIT_PERF_7519_UNTRACKED_CACHE"
> +	then
> +		git config core.untrackedCache "$GIT_PERF_7519_UNTRACKED_CACHE"
> +	else
> +		if test_have_prereq UNTRACKED_CACHE
> +		then
> +			git config core.untrackedCache true
> +		else
> +			git config core.untrackedCache false
> +		fi
> +	fi &&
> +
> +	if test -n "$GIT_PERF_7519_SPLIT_INDEX"
> +	then
> +		git config core.splitIndex "$GIT_PERF_7519_SPLIT_INDEX"
> +	fi &&
> +
> +	# Hook scaffolding
> +	mkdir .git/hooks &&
> +	cp ../../../templates/hooks--query-fsmonitor.sample .git/hooks/query-fsmonitor &&
> +
> +	# have Watchman monitor the test folder
> +	watchman watch "$GIT_WORK_TREE" &&
> +	watchman watch-list | grep -q -F "$GIT_WORK_TREE"
> +'
> +
> +# Worst case without fsmonitor
> +test_expect_success "clear fs cache" '
> +	git config core.fsmonitor false &&
> +	flush_disk_cache
> +'
> +test_perf "status (fsmonitor=false, cold fs cache)" '
> +	git status
> +'
> +
> +# Best case without fsmonitor
> +test_perf "status (fsmonitor=false, warm fs cache)" '
> +	git status
> +'
> +
> +# Let's see if -uno & -uall make any difference
> +test_expect_success "clear fs cache" '
> +	flush_disk_cache
> +'
> +test_perf "status -uno (fsmonitor=false, cold fs cache)" '
> +	git status -uno
> +'
> +
> +test_expect_success "clear fs cache" '
> +	flush_disk_cache
> +'
> +test_perf "status -uall (fsmonitor=false, cold fs cache)" '
> +	git status -uall
> +'
> +
> +# The first run with core.fsmonitor=true has to do a normal scan and write
> +# out the index extension.
> +test_expect_success "populate extension" '
> +	# core.preloadIndex defeats the benefits of core.fsMonitor as it
> +	# calls lstat for the index entries. Turn it off as _not_ doing
> +	# the work is faster than doing the work across multiple threads.
> +	git config core.fsmonitor true &&
> +	git config core.preloadIndex false &&
> +	git status
> +'
> +
> +# Worst case with fsmonitor
> +test_expect_success "shutdown fsmonitor, clear fs cache" '
> +	watchman shutdown-server &&
> +	flush_disk_cache
> +'
> +test_perf "status (fsmonitor=true, cold fs cache, cold fsmonitor)" '
> +	git status
> +'
> +
> +# Best case with fsmonitor
> +test_perf "status (fsmonitor=true, warm fs cache, warm fsmonitor)" '
> +	git status
> +'
> +
> +# Best improved with fsmonitor (compare to worst case without fsmonitor)
> +test_expect_success "clear fs cache" '
> +	flush_disk_cache
> +'
> +test_perf "status (fsmonitor=true, cold fs cache, warm fsmonitor)" '
> +	git status
> +'
> +
> +# Let's see if -uno & -uall make any difference
> +test_expect_success "clear fs cache" '
> +	flush_disk_cache
> +'
> +test_perf "status -uno (fsmonitor=true, cold fs cache)" '
> +	git status -uno
> +'
> +
> +test_expect_success "clear fs cache" '
> +	flush_disk_cache
> +'
> +test_perf "status -uall (fsmonitor=true, cold fs cache)" '
> +	git status -uall
> +'
> +
> +test_expect_success "cleanup" '
> +	watchman watch-del "$GIT_WORK_TREE" &&
> +	watchman shutdown-server
> +'
> +
> +test_done
>