From f8c95d2a25b5b0ff4c8d50c57e4ac6195dcd82f6 Mon Sep 17 00:00:00 2001 From: Willy Tarreau Date: Tue, 12 Jun 2012 09:16:56 +0200 Subject: [PATCH] OPTIM: halog: improve cold-cache behaviour when loading a file 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. --- contrib/halog/halog.c | 9 +++++++++ 1 file changed, 9 insertions(+) diff --git a/contrib/halog/halog.c b/contrib/halog/halog.c index 250623d827..448e5c0a83 100644 --- a/contrib/halog/halog.c +++ b/contrib/halog/halog.c @@ -672,6 +672,15 @@ int main(int argc, char **argv) else if (filter & FILT_COUNT_ONLY) 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 && !(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 */ -- 2.47.3