Hi All, As we have seen the regression of more than 45% with "*backend_flush_after*" enabled and set to its default value i.e. 128KB or even when it is set to some higher value like 2MB, i think we should disable it such that it does not impact the read write performance and here is the attached patch for the same. Please have a look and let me know your thoughts on this. Thanks!
With Regards, Ashutosh Sharma EnterpriseDB: http://www.enterprisedb.com On Sun, May 15, 2016 at 1:26 AM, Fabien COELHO <coe...@cri.ensmp.fr> wrote: > > These raw tps suggest that {backend,bgwriter}_flush_after should better be >>> zero for this kind of load.Whether it should be the default is unclear >>> yet, >>> because as Andres pointed out this is one kind of load. >>> >> >> FWIW, I don't think {backend,bgwriter} are the same here. It's primarily >> backend that matters. >> > > Indeed, I was a little hasty to put bgwriter together based on this report. > > I'm a little wary of "bgwriter_flush_after" though, I would not be > surprised if someone reports some regressions, although probably not with a > pgbench tpcb kind of load. > > -- > Fabien. >
diff --git a/src/include/storage/bufmgr.h b/src/include/storage/bufmgr.h index 38b6027..fff7104 100644 --- a/src/include/storage/bufmgr.h +++ b/src/include/storage/bufmgr.h @@ -60,7 +60,7 @@ extern PGDLLIMPORT int NBuffers; /* FIXME: Also default to on for mmap && msync(MS_ASYNC)? */ #ifdef HAVE_SYNC_FILE_RANGE #define DEFAULT_CHECKPOINT_FLUSH_AFTER 32 -#define DEFAULT_BACKEND_FLUSH_AFTER 16 +#define DEFAULT_BACKEND_FLUSH_AFTER 0 #define DEFAULT_BGWRITER_FLUSH_AFTER 64 #else #define DEFAULT_CHECKPOINT_FLUSH_AFTER 0
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