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Re: [PATCHES] SRA Win32 sync() code

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Hannu Krosing <hannu(at)tm(dot)ee>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,PostgreSQL-patches <pgsql-patches(at)postgresql(dot)org>,PostgreSQL Win32 port list <pgsql-hackers-win32(at)postgresql(dot)org>
Subject: Re: [PATCHES] SRA Win32 sync() code
Date: 2003-11-17 15:33:49
Message-ID: 200311171533.hAHFXns05677@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackerspgsql-hackers-win32pgsql-patches
Hannu Krosing wrote:
> Bruce Momjian kirjutas E, 17.11.2003 kell 03:58:
> 
> > 
> > OK, let me give you my logic and you can tell me where I am wrong.
> > 
> > First, how many backend can a single write process support if all the
> > backends are doing insert/update/deletes?  5?  10?  Let's assume 10. 
> > Second, once we change write to write/fsync, how much slower will that
> > be?  100x, 1000x?  Let's say 10x.
> > 
> > So, by my logic, if we have 100 backends all doing updates, we will need
> > 10 * 100 or 1000 writer processes or threads to keep up with that load. 
> > That seems quite excessive to me from a context switching and process
> > overhead perspective.
> > 
> > Where am I wrong?
> 
> Maybe you meant 100/10 instead of 100*10 ;)

I figured 10 backends, but using fsync, they are not 100x slower (10 *
100).  However, testing shows fsync is only 3x slower.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
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