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Re: making use of large TLB pages

From: Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us>
To: Neil Conway <neilc(at)samurai(dot)com>
Cc: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>,PostgreSQL Hackers <pgsql-hackers(at)postgresql(dot)org>
Subject: Re: making use of large TLB pages
Date: 2002-09-29 13:38:27
Message-ID: 200209291338.g8TDcRE06330@candle.pha.pa.us (view raw or flat)
Thread:
Lists: pgsql-hackers
Neil Conway wrote:
> Bruce Momjian <pgman(at)candle(dot)pha(dot)pa(dot)us> writes:
> > 	Is TLB Linux-only?
> 
> Well, the "TLB" is a feature of the CPU, so no. Many modern processors
> support large TLB pages in some fashion.
> 
> However, the specific API for using large TLB pages differs between
> operating systems. The API I'm planning to implement is the one
> provided by recent versions of Linux (2.5.38+).
> 
> I've only looked briefly at enabling the usage of large pages on other
> operating systems. On Solaris, we already use large pages (due to
> using Intimate Shared Memory). On HPUX, you apparently need call
> chattr on the executable for it to use large pages. AFAIK the BSDs
> don't support large pages for user-land apps -- if I'm incorrect, let
> me know.
> 
> > 	Why use it and non SysV memory?
> 
> It's faster, at least in theory. I posted these links at the start of
> the thread:
> 
>         http://lwn.net/Articles/6535/
>         http://lwn.net/Articles/10293/
> 
> > 	Is it a lot of code?
> 
> I haven't implemented it yet, so I'm not sure. However, I don't think
> it will be a lot of code.

OK, personally, I would like to see an actual speedup of PostgreSQL
queries before I would apply such a OS-specific, version-specific patch.

-- 
  Bruce Momjian                        |  http://candle.pha.pa.us
  pgman(at)candle(dot)pha(dot)pa(dot)us               |  (610) 359-1001
  +  If your life is a hard drive,     |  13 Roberts Road
  +  Christ can be your backup.        |  Newtown Square, Pennsylvania 19073

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