From: Olivier Galibert <galibert@pobox.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <jens.axboe@oracle.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Linux Memory Management List <linux-mm@kvack.org>,
linux-fsdevel@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 10/11] readahead: dont do start-of-file readahead after lseek()
Date: Tue, 2 Feb 2010 19:48:31 +0100 [thread overview]
Message-ID: <20100202184831.GD75577@dspnet.fr.eu.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1002021037110.3664@localhost.localdomain>
On Tue, Feb 02, 2010 at 10:40:41AM -0800, Linus Torvalds wrote:
> IOW, if you start off with a SEEK_END, I think it's reasonable to expect
> it to _not_ read the whole thing.
I've seen a lot of:
int fd = open(...);
size = lseek(fd, 0, SEEK_END);
lseek(fd, 0, SEEK_SET);
data = malloc(size);
read(fd, data, size);
close(fd);
Why not fstat? I don't know. Perhaps a case of cargo culting,
perhaps a case of "other unixes suck for portability"[1]. But it's
probably still there a lot in real code.
OG.
[1] In the hpux, dgux, sunos, etc sense. Not to be taken as a comment
on modern BSDs.
WARNING: multiple messages have this Message-ID (diff)
From: Olivier Galibert <galibert@pobox.com>
To: Linus Torvalds <torvalds@linux-foundation.org>
Cc: Wu Fengguang <fengguang.wu@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <jens.axboe@oracle.com>,
Peter Zijlstra <a.p.zijlstra@chello.nl>,
Linux Memory Management List <linux-mm@kvack.org>,
linux-fsdevel@vger.kernel.org,
LKML <linux-kernel@vger.kernel.org>
Subject: Re: [PATCH 10/11] readahead: dont do start-of-file readahead after lseek()
Date: Tue, 2 Feb 2010 19:48:31 +0100 [thread overview]
Message-ID: <20100202184831.GD75577@dspnet.fr.eu.org> (raw)
In-Reply-To: <alpine.LFD.2.00.1002021037110.3664@localhost.localdomain>
On Tue, Feb 02, 2010 at 10:40:41AM -0800, Linus Torvalds wrote:
> IOW, if you start off with a SEEK_END, I think it's reasonable to expect
> it to _not_ read the whole thing.
I've seen a lot of:
int fd = open(...);
size = lseek(fd, 0, SEEK_END);
lseek(fd, 0, SEEK_SET);
data = malloc(size);
read(fd, data, size);
close(fd);
Why not fstat? I don't know. Perhaps a case of cargo culting,
perhaps a case of "other unixes suck for portability"[1]. But it's
probably still there a lot in real code.
OG.
[1] In the hpux, dgux, sunos, etc sense. Not to be taken as a comment
on modern BSDs.
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next prev parent reply other threads:[~2010-02-02 18:48 UTC|newest]
Thread overview: 82+ messages / expand[flat|nested] mbox.gz Atom feed top
2010-02-02 15:28 [PATCH 00/11] [RFC] 512K readahead size with thrashing safe readahead Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 01/11] readahead: limit readahead size for small devices Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 19:38 ` Jens Axboe
2010-02-02 19:38 ` Jens Axboe
2010-02-03 6:13 ` Wu Fengguang
2010-02-03 6:13 ` Wu Fengguang
2010-02-03 8:23 ` Jens Axboe
2010-02-03 8:23 ` Jens Axboe
2010-02-04 8:24 ` Clemens Ladisch
2010-02-04 8:24 ` Clemens Ladisch
2010-02-04 13:00 ` Wu Fengguang
2010-02-04 13:00 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 02/11] readahead: bump up the default readahead size Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 03/11] readahead: introduce {MAX|MIN}_READAHEAD_PAGES macros for ease of use Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 04/11] readahead: replace ra->mmap_miss with ra->ra_flags Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 05/11] readahead: retain inactive lru pages to be accessed soon Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 06/11] readahead: thrashing safe context readahead Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 07/11] readahead: record readahead patterns Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 08/11] readahead: add tracing event Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-12 16:19 ` Steven Rostedt
2010-02-12 16:19 ` Steven Rostedt
2010-02-14 3:56 ` Wu Fengguang
2010-02-14 3:56 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 09/11] readahead: add /debug/readahead/stats Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` [PATCH 10/11] readahead: dont do start-of-file readahead after lseek() Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 17:39 ` Linus Torvalds
2010-02-02 17:39 ` Linus Torvalds
2010-02-02 18:13 ` Olivier Galibert
2010-02-02 18:13 ` Olivier Galibert
2010-02-02 18:40 ` Linus Torvalds
2010-02-02 18:40 ` Linus Torvalds
2010-02-02 18:48 ` Olivier Galibert [this message]
2010-02-02 18:48 ` Olivier Galibert
2010-02-02 19:14 ` Linus Torvalds
2010-02-02 19:14 ` Linus Torvalds
2010-02-02 19:59 ` david
2010-02-02 19:59 ` david
2010-02-02 20:22 ` Linus Torvalds
2010-02-02 20:22 ` Linus Torvalds
2010-02-02 15:28 ` [PATCH 11/11] radixtree: speed up next/prev hole search Wu Fengguang
2010-02-02 15:28 ` Wu Fengguang
2010-02-02 22:38 ` [PATCH 00/11] [RFC] 512K readahead size with thrashing safe readahead Vivek Goyal
2010-02-02 22:38 ` Vivek Goyal
2010-02-02 22:38 ` Vivek Goyal
2010-02-02 23:17 ` Vivek Goyal
2010-02-02 23:17 ` Vivek Goyal
2010-02-03 6:27 ` Wu Fengguang
2010-02-03 6:27 ` Wu Fengguang
2010-02-03 15:24 ` Vivek Goyal
2010-02-03 15:24 ` Vivek Goyal
2010-02-03 15:58 ` Vivek Goyal
2010-02-03 15:58 ` Vivek Goyal
2010-02-03 16:55 ` Fwd: " Mike Snitzer
2010-02-04 13:21 ` Wu Fengguang
2010-02-04 13:21 ` Wu Fengguang
2010-02-04 15:52 ` Vivek Goyal
2010-02-04 15:52 ` Vivek Goyal
2010-02-04 13:44 ` Wu Fengguang
2010-02-04 13:44 ` Wu Fengguang
-- strict thread matches above, loose matches on Subject: below --
2010-02-07 4:10 [PATCH 00/11] " Wu Fengguang
2010-02-07 4:10 ` [PATCH 10/11] readahead: dont do start-of-file readahead after lseek() Wu Fengguang
2010-02-07 4:10 ` Wu Fengguang
2010-02-07 4:10 ` Wu Fengguang
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