[PATCH v4 9/9] lstat_cache(): print a warning if doing ping-pong between cache types
- From
- Kjetil Barvik <barvik@broadpark.no>
- Date
- Feb 9, 2009, 20:54 UTC
- Message-ID
- <82c70ec625052b93dae3f7b24a79fe058257f494.1234211595.git.barvik@broadpark.no>
- In-Reply-To
- <cover.1234211594.git.barvik@broadpark.no>
This is a debug patch which is only to be used while the lstat_cache() is in the test stage, and should be removed/reverted before the final relase.
I think it should be useful to catch these warnings, as I it could be an indication of that the cache would not be very effective if it is doing ping-pong by switching between different cache types too many times.
Also, if someone is experimenting with the lstat_cache(), this patch will maybe be useful while debugging.
If someone is able to trigger the warning, then send a mail to the GIT mailing list, containing the first 15 lines of the warning, and a short description of the GIT commands to trigger the warnings.
I hope someone is willing to use this patch for a while, to be able to catch possible ping-pong's.
Signed-off-by: Kjetil Barvik <barvik@broadpark.no> --- symlinks.c | 23 +++++++++++++++++++++++ 1 files changed, 23 insertions(+), 0 deletions(-)
diff --git a/symlinks.c b/symlinks.c index 1d6b35b..cb255a3 100644 --- a/symlinks.c +++ b/symlinks.c @@ -51,6 +51,11 @@ static inline void reset_lstat_cache(void) */ } +#define SWITCHES_BEFORE_WARNING 10 +static unsigned int cache_switches, number_of_warnings; +static unsigned int current_cache_func, last_cache_func; +static unsigned int total_calls; + #define FL_DIR (1 << 0) #define FL_NOENT (1 << 1) #define FL_SYMLINK (1 << 2) @@ -77,6 +82,7 @@ static int lstat_cache(const char *name, int len, int match_flags, ret_flags, save_flags, max_len, ret; struct stat st; + total_calls++; if (cache.track_flags != track_flags || cache.prefix_len_stat_func != prefix_len_stat_func) { /* @@ -88,6 +94,17 @@ static int lstat_cache(const char *name, int len, cache.track_flags = track_flags; cache.prefix_len_stat_func = prefix_len_stat_func; match_len = last_slash = 0; + cache_switches++; + if (cache_switches > SWITCHES_BEFORE_WARNING) { + if (number_of_warnings < 10 || number_of_warnings % 1000 == 0) + printf("warning from %s:%d cache_switches:%u > %u "\ + "(current:%u last:%u total:%u)\n", + __FILE__, __LINE__, + cache_switches, SWITCHES_BEFORE_WARNING, + current_cache_func, last_cache_func, + total_calls); + number_of_warnings++; + } } else { /* * Check to see if we have a match from the cache for @@ -216,6 +233,8 @@ void clear_lstat_cache(void) */ int has_symlink_leading_path(const char *name, int len) { + last_cache_func = current_cache_func; + current_cache_func = 1; return lstat_cache(name, len, FL_SYMLINK|FL_DIR, USE_ONLY_LSTAT) & FL_SYMLINK; @@ -227,6 +246,8 @@ int has_symlink_leading_path(const char *name, int len) */ int has_symlink_or_noent_leading_path(const char *name, int len) { + last_cache_func = current_cache_func; + current_cache_func = 2; return lstat_cache(name, len, FL_SYMLINK|FL_NOENT|FL_DIR, USE_ONLY_LSTAT) & (FL_SYMLINK|FL_NOENT); @@ -241,6 +262,8 @@ int has_symlink_or_noent_leading_path(const char *name, int len) */ int has_dirs_only_path(const char *name, int len, int prefix_len) { + last_cache_func = current_cache_func; + current_cache_func = 3; return lstat_cache(name, len, FL_DIR|FL_FULLPATH, prefix_len) & FL_DIR;
-- 1.6.1.349.g99fa5