From: "Hua Zhong" <hzhong@cisco.com>
To: "'Andy Isaacson'" <adi@hexapodia.org>
Cc: <linux-kernel@vger.kernel.org>
Subject: RE: Is there a "make hole" (truncate in middle) syscall?
Date: Thu, 11 Dec 2003 11:15:28 -0800 [thread overview]
Message-ID: <017c01c3c01b$232bd130$d43147ab@amer.cisco.com> (raw)
In-Reply-To: <20031211125806.B2422@hexapodia.org>
> The abstract interface for make_hole() is simple, but it turns into a
> pretty expensive filesystem operation, I think. After many cycles of
> free/allocate, your file would be badly fragmented across the
> filesystem.
Understood. Two filesystems we are using: tmpfs and ext3. For the
former, fragmentation doesn't matter.
Hey, I think when I get some cycles I can try to implement this for
tmpfs (since it's simpler) myself, and post a patch. :-) But before
that, I want to make sure it's doable.
> You'll probably get better overall performance by keeping
> track of how "sparse" your file is (you could compare st_blocks versus
> how many blocks you have allocated in your tree structure)
> and re-write
> it when you're wasting more than, say, 20% of the allocated space.
>
> It turns into an interesting problem if you don't want to double your
> space requirements during the re-write process. You could write the
> new file "backwards", one MB at a time, truncating the
> previous file at
> each step to free up the blocks. You'd end up with contiguous 1MB
> chunks, which given your tree organization is probably good
> enough. If
> you wanted really good streaming performance you'd want to do bigger
> chunks (or just write the file from the beginning, or use the
> pre-allocation APIs that I think XFS provides).
>
> -andy
>
next prev parent reply other threads:[~2003-12-11 19:15 UTC|newest]
Thread overview: 59+ messages / expand[flat|nested] mbox.gz Atom feed top
2003-12-04 20:32 Is there a "make hole" (truncate in middle) syscall? Rob Landley
2003-12-04 20:55 ` Måns Rullgård
2003-12-04 21:10 ` Szakacsits Szabolcs
2003-12-05 0:02 ` Rob Landley
2003-12-04 22:33 ` Szakacsits Szabolcs
2003-12-05 11:22 ` Helge Hafting
2003-12-05 12:11 ` Måns Rullgård
2003-12-05 22:41 ` Mike Fedyk
2003-12-05 23:25 ` Måns Rullgård
2003-12-05 23:33 ` Szakacsits Szabolcs
2003-12-05 23:25 ` Szakacsits Szabolcs
2003-12-04 21:48 ` Mike Fedyk
2003-12-04 23:59 ` Rob Landley
2003-12-05 22:42 ` Olaf Titz
2003-12-04 22:53 ` Peter Chubb
2003-12-05 1:04 ` Philippe Troin
2003-12-05 2:39 ` Peter Chubb
2003-12-08 4:03 ` bill davidsen
2003-12-04 23:23 ` Andy Isaacson
2003-12-04 23:42 ` Szakacsits Szabolcs
2003-12-05 2:03 ` Mike Fedyk
2003-12-05 7:09 ` Ville Herva
2003-12-05 11:22 ` Anton Altaparmakov
2003-12-05 11:44 ` viro
2003-12-05 14:27 ` Anton Altaparmakov
2003-12-05 21:00 ` sparse file performance (was Re: Is there a "make hole" (truncate in middle) syscall?) Andy Isaacson
2003-12-05 21:12 ` Linus Torvalds
2003-12-08 20:43 ` Andy Isaacson
2003-12-11 5:13 ` Is there a "make hole" (truncate in middle) syscall? Hua Zhong
2003-12-11 6:19 ` Rob Landley
2003-12-11 18:58 ` Andy Isaacson
2003-12-11 19:15 ` Hua Zhong [this message]
2003-12-11 19:43 ` Andreas Dilger
2003-12-12 21:37 ` Daniel Phillips
2003-12-11 19:48 ` Jörn Engel
2003-12-11 19:55 ` Hua Zhong
2003-12-11 19:58 ` Andy Isaacson
2003-12-12 12:18 ` Jörn Engel
2003-12-12 15:40 ` Andy Isaacson
2003-12-12 16:03 ` Jörn Engel
2003-12-11 20:32 ` Rob Landley
2003-12-12 12:55 ` Jörn Engel
2003-12-12 13:28 ` Vladimir Saveliev
2003-12-12 13:43 ` Jörn Engel
2003-12-12 13:52 ` Vladimir Saveliev
2003-12-12 14:04 ` Jörn Engel
2003-12-12 13:53 ` Rob Landley
2003-12-12 14:01 ` Vladimir Saveliev
2003-12-12 21:35 ` Rob Landley
2003-12-15 10:00 ` Vladimir Saveliev
2003-12-15 11:52 ` Rob Landley
2003-12-15 13:26 ` Jörn Engel
2003-12-12 13:39 ` Rob Landley
2003-12-12 13:56 ` Jörn Engel
2003-12-12 14:24 ` Jörn Engel
2003-12-12 21:37 ` Rob Landley
2003-12-15 12:47 ` Jörn Engel
2003-12-16 5:43 ` Rob Landley
2003-12-16 11:05 ` Jörn Engel
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