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From: Stephen Frost <sfrost@snowman.net>
To: Benjamin LaHaise <bcrl@kvack.org>
Cc: Andres Freund <andres@anarazel.de>,
	Matthew Wilcox <matthew@wil.cx>, Andi Kleen <andi@firstfloor.org>,
	viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, robertmhaas@gmail.com,
	pgsql-hackers@postgresql.org
Subject: Re: [HACKERS] Improve lseek scalability v3
Date: Mon, 19 Sep 2011 08:31:00 -0400	[thread overview]
Message-ID: <20110919123100.GJ12765@tamriel.snowman.net> (raw)
In-Reply-To: <20110916200817.GD28519@kvack.org>

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* Benjamin LaHaise (bcrl@kvack.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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WARNING: multiple messages have this Message-ID (diff)
From: Stephen Frost <sfrost@snowman.net>
To: Benjamin LaHaise <bcrl@kvack.org>
Cc: Andres Freund <andres@anarazel.de>,
	Matthew Wilcox <matthew@wil.cx>, Andi Kleen <andi@firstfloor.org>,
	viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org,
	linux-kernel@vger.kernel.org, robertmhaas@gmail.com,
	pgsql-hackers@postgresql.org
Subject: Re: Improve lseek scalability v3
Date: Mon, 19 Sep 2011 08:31:00 -0400	[thread overview]
Message-ID: <20110919123100.GJ12765@tamriel.snowman.net> (raw)
In-Reply-To: <20110916200817.GD28519@kvack.org>

[-- Attachment #1: Type: text/plain, Size: 527 bytes --]

* Benjamin LaHaise (bcrl@kvack.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

[-- Attachment #2: Digital signature --]
[-- Type: application/pgp-signature, Size: 198 bytes --]

  parent reply	other threads:[~2011-09-19 12:40 UTC|newest]

Thread overview: 54+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2011-09-15 23:06 Improve lseek scalability v3 Andi Kleen
2011-09-15 23:06 ` [PATCH 1/7] BTRFS: Fix lseek return value for error Andi Kleen
2011-09-15 23:47   ` Thomas Gleixner
2011-09-16 15:48   ` Christoph Hellwig
2011-09-16 16:38     ` Andi Kleen
2011-09-17  6:10     ` Jeff Liu
2011-09-17 23:03       ` Andreas Dilger
2011-09-18  1:46         ` Andi Kleen
2011-09-18  7:29           ` Jeff Liu
2011-09-18  8:42             ` Marco Stornelli
2011-09-18 10:33               ` Jeff liu
2011-09-18 10:33                 ` Jeff liu
2011-09-18 14:55                 ` Chris Mason
2011-09-18 14:55                   ` Chris Mason
2011-09-18 14:55                   ` Chris Mason
2011-09-19 17:52                   ` Andi Kleen
2011-09-19 19:30                     ` Chris Mason
2011-09-19 19:59                       ` Andi Kleen
2011-09-19 22:55                         ` Chris Mason
2011-09-15 23:06 ` [PATCH 2/7] VFS: Do (nearly) lockless generic_file_llseek Andi Kleen
2011-09-15 23:06 ` [PATCH 3/7] VFS: Make generic lseek lockless safe Andi Kleen
2011-09-15 23:06 ` [PATCH 4/7] VFS: Add generic_file_llseek_size Andi Kleen
2011-09-16 15:50   ` Christoph Hellwig
2011-09-15 23:06 ` [PATCH 5/7] LSEEK: EXT4: Replace cut'n'pasted llseek code with generic_file_llseek_size Andi Kleen
2011-09-15 23:06 ` [PATCH 6/7] LSEEK: NFS: Drop unnecessary locking in llseek Andi Kleen
2011-09-15 23:06 ` [PATCH 7/7] LSEEK: BTRFS: Avoid i_mutex for SEEK_{CUR,SET,END} Andi Kleen
2011-09-16 13:00 ` Improve lseek scalability v3 Matthew Wilcox
2011-09-16 13:19   ` Josef Bacik
2011-09-16 14:16   ` Andres Freund
2011-09-16 14:23     ` Andi Kleen
2011-09-16 14:41       ` Andres Freund
2011-09-16 15:36     ` Matthew Wilcox
2011-09-16 17:27       ` Andres Freund
2011-09-16 17:39         ` [HACKERS] " Alvaro Herrera
2011-09-16 17:39           ` Alvaro Herrera
2011-09-16 17:50           ` [HACKERS] " Andi Kleen
2011-09-16 20:08         ` Benjamin LaHaise
2011-09-16 21:02           ` Andres Freund
2011-09-16 21:05             ` [HACKERS] " Andres Freund
2011-09-16 22:44           ` Greg Stark
2011-09-19 12:31           ` Stephen Frost [this message]
2011-09-19 12:31             ` Stephen Frost
2011-09-19 13:25             ` [HACKERS] " Matthew Wilcox
2011-09-20  7:18               ` Marco Stornelli
2011-09-20  7:18                 ` Marco Stornelli
2011-09-19 13:30             ` Robert Haas
2011-09-16 14:26   ` Andres Freund
2011-10-01 20:46 ` Andres Freund
2011-10-01 20:49   ` [PATCH 1/2] LSEEK: BTRFS: Avoid i_mutex for SEEK_{CUR,SET,END} Andres Freund
2011-11-02  8:29     ` Christoph Hellwig
2011-11-05 15:27       ` Chris Mason
2012-03-07 17:16         ` Andres Freund
2011-10-01 20:50   ` [PATCH 2/2] btrfs: Don't have multiple paths to error out in btrfs_file_llseek Andres Freund
2011-10-02  5:28   ` Improve lseek scalability v3 Andi Kleen

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