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OPTIM: halog: improve cold-cache behaviour when loading a file

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Using posix_fadvise() it is possible to tell the system that we're
going to read a whole file at once. The kernel then doubles the
read-ahead size for this file. On Linux with an SSD, this has improved
cold-cache performance by around 20%. Hot-cache is not affected at all.
This commit is contained in:
Willy Tarreau 2012-06-12 09:16:56 +02:00
parent 419a598eae
commit f8c95d2a25
1 changed files with 9 additions and 0 deletions
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9
contrib/halog/halog.c
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@ -672,6 +672,15 @@ int main(int argc, char **argv)
else if (filter & FILT_COUNT_ONLY) else if (filter & FILT_COUNT_ONLY)
line_filter = NULL; line_filter = NULL;
#if defined(POSIX_FADV_SEQUENTIAL)
/* around 20% performance improvement is observed on Linux with this
* on cold-cache. Surprizingly, WILLNEED is less performant. Don't
* use NOREUSE as it flushes the cache and prevents easy data
* manipulation on logs!
*/
posix_fadvise(0, 0, 0, POSIX_FADV_SEQUENTIAL);
#endif
if (!line_filter && if (!line_filter &&
!(filter & (FILT_HTTP_ONLY|FILT_TIME_RESP|FILT_ERRORS_ONLY|FILT_HTTP_STATUS|FILT_QUEUE_ONLY|FILT_QUEUE_SRV_ONLY|FILT_TERM_CODE_NAME))) { !(filter & (FILT_HTTP_ONLY|FILT_TIME_RESP|FILT_ERRORS_ONLY|FILT_HTTP_STATUS|FILT_QUEUE_ONLY|FILT_QUEUE_SRV_ONLY|FILT_TERM_CODE_NAME))) {
/* read the whole file at once first */ /* read the whole file at once first */