On Wed, Jan 29, 2014 at 9:03 AM, KONDO Mitsumasa < kondo.mitsum...@lab.ntt.co.jp> wrote:
> (2014/01/29 15:51), Tom Lane wrote: > > KONDO Mitsumasa <kondo.mitsum...@lab.ntt.co.jp> writes: > >> By the way, latest pg_stat_statement might affect performance in > Windows system. > >> Because it uses fflush() system call every creating new entry in > >> pg_stat_statements, and it calls many fread() to warm file cache. > > This statement doesn't seem to have much to do with the patch as > > committed. There are no fflush calls, and no notion of warming the > > file cache either. > Oh, all right. > > > We do assume that the OS is smart enough to keep > > a frequently-read file in cache ... is Windows too stupid for that? > I don't know about it. But I think Windows cache feature is stupid. > It seems to always write/read data to/from disk, nevertheless having large > memory... > I'd like to know test result on Windows, if we can... > > I am quite certain the Windows cache is *not* that stupid, and hasn't been since the Windows 3.1 days. If you want to make certain, set FILE_ATTRIBUTE_TEMPORARY when the file is opened, then it will work really hard not to write it to disk - harder than most Linux fs'es do AFAIK. This should of course only be done if we don't mind it going away :) As per port/open.c, pg will set this when O_SHORT_LIVED is specified. But AFAICT, we don't actually use this *anywhere* in the backend? Perhaps we should for this - and also for the pgstat files? (I may have missed a codepath, only had a minute to do some greping) -- Magnus Hagander Me: http://www.hagander.net/ Work: http://www.redpill-linpro.com/
