linux-kernel - Re: [HACKERS] Improve lseek scalability v3

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Message-ID: <20110919123100.GJ12765@tamriel.snowman.net>
Date:	Mon, 19 Sep 2011 08:31:00 -0400
From:	Stephen Frost <sfrost@...wman.net>
To:	Benjamin LaHaise <bcrl@...ck.org>
Cc:	Andres Freund <andres@...razel.de>,
	Matthew Wilcox <matthew@....cx>,
	Andi Kleen <andi@...stfloor.org>, viro@...iv.linux.org.uk,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	robertmhaas@...il.com, pgsql-hackers@...tgresql.org
Subject: Re: [HACKERS] Improve lseek scalability v3

* Benjamin LaHaise (bcrl@...ck.org) wrote:
> For such tables, can't Postgres track the size of the file internally?  I'm 
> assuming it's keeping file descriptors open on the tables it manages, in 
> which case when it writes to a file to extend it, the internally stored size 
> could be updated.  Not making a syscall at all would scale far better than 
> even a modified lseek() will perform.

We'd have to have it in shared memory and have a lock around it, it
wouldn't be cheap at all.

	Thanks,
		
		Stephen

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