From 238b72e0690f78044be46af458d29333a330910f Mon Sep 17 00:00:00 2001 From: Karsten Blees Date: Sun, 8 Sep 2013 14:23:27 +0200 Subject: [PATCH] add infrastructure for read-only file system level caches Add a macro to mark code sections that only read from the file system, along with a config option and documentation. This facilitates implementation of relatively simple file system level caches without the need to synchronize with the file system. Enable read-only sections for 'git status' and preload_index. Signed-off-by: Karsten Blees --- Documentation/config/core.txt | 6 ++++++ builtin/commit.c | 1 + compat/mingw.c | 6 ++++++ compat/mingw.h | 2 ++ git-compat-util.h | 15 +++++++++++++++ preload-index.c | 2 ++ 6 files changed, 32 insertions(+) diff --git a/Documentation/config/core.txt b/Documentation/config/core.txt index 7e9b6c8f4c..f12ebc8db0 100644 --- a/Documentation/config/core.txt +++ b/Documentation/config/core.txt @@ -551,6 +551,12 @@ relatively high IO latencies. When enabled, Git will do the index comparison to the filesystem data in parallel, allowing overlapping IO's. Defaults to true. +core.fscache:: + Enable additional caching of file system data for some operations. ++ +Git for Windows uses this to bulk-read and cache lstat data of entire +directories (instead of doing lstat file by file). + core.unsetenvvars:: Windows-only: comma-separated list of environment variables' names that need to be unset before spawning any other process. diff --git a/builtin/commit.c b/builtin/commit.c index 2986553d5f..ffa60928ad 100644 --- a/builtin/commit.c +++ b/builtin/commit.c @@ -1366,6 +1366,7 @@ int cmd_status(int argc, const char **argv, const char *prefix) PATHSPEC_PREFER_FULL, prefix, argv); + enable_fscache(1); if (status_format != STATUS_FORMAT_PORCELAIN && status_format != STATUS_FORMAT_PORCELAIN_V2) progress_flag = REFRESH_PROGRESS; diff --git a/compat/mingw.c b/compat/mingw.c index f7d2c64dcf..0a5f318cf0 100644 --- a/compat/mingw.c +++ b/compat/mingw.c @@ -227,6 +227,7 @@ enum hide_dotfiles_type { static enum hide_dotfiles_type hide_dotfiles = HIDE_DOTFILES_DOTGITONLY; static char *unset_environment_variables; +int core_fscache; int mingw_core_config(const char *var, const char *value, void *cb) { @@ -238,6 +239,11 @@ int mingw_core_config(const char *var, const char *value, void *cb) return 0; } + if (!strcmp(var, "core.fscache")) { + core_fscache = git_config_bool(var, value); + return 0; + } + if (!strcmp(var, "core.unsetenvvars")) { free(unset_environment_variables); unset_environment_variables = xstrdup(value); diff --git a/compat/mingw.h b/compat/mingw.h index d2af15f417..951f9ece67 100644 --- a/compat/mingw.h +++ b/compat/mingw.h @@ -30,6 +30,8 @@ typedef _sigset_t sigset_t; #undef _POSIX_THREAD_SAFE_FUNCTIONS #endif +extern int core_fscache; + extern int mingw_core_config(const char *var, const char *value, void *cb); #define platform_core_config mingw_core_config diff --git a/git-compat-util.h b/git-compat-util.h index 736b324f2e..2856429105 100644 --- a/git-compat-util.h +++ b/git-compat-util.h @@ -1258,6 +1258,21 @@ static inline int is_missing_file_error(int errno_) return (errno_ == ENOENT || errno_ == ENOTDIR); } +/* + * Enable/disable a read-only cache for file system data on platforms that + * support it. + * + * Implementing a live-cache is complicated and requires special platform + * support (inotify, ReadDirectoryChangesW...). enable_fscache shall be used + * to mark sections of git code that extensively read from the file system + * without modifying anything. Implementations can use this to cache e.g. stat + * data or even file content without the need to synchronize with the file + * system. + */ +#ifndef enable_fscache +#define enable_fscache(x) /* noop */ +#endif + extern int cmd_main(int, const char **); /* diff --git a/preload-index.c b/preload-index.c index e73600ee78..5e8791c43e 100644 --- a/preload-index.c +++ b/preload-index.c @@ -120,6 +120,7 @@ void preload_index(struct index_state *index, pthread_mutex_init(&pd.mutex, NULL); } + enable_fscache(1); for (i = 0; i < threads; i++) { struct thread_data *p = data+i; int err; @@ -145,6 +146,7 @@ void preload_index(struct index_state *index, stop_progress(&pd.progress); trace_performance_leave("preload index"); + enable_fscache(0); } int repo_read_index_preload(struct repository *repo,