[PATCH 0/4] Replace lseek..write/read to pwrite/pread

Petr Tesarik ptesarik at suse.cz
Wed Apr 30 04:53:04 PDT 2014

On Wed, 30 Apr 2014 20:41:38 +0900 (JST)
HATAYAMA Daisuke <d.hatayama at jp.fujitsu.com> wrote:

> From: Wang Nan <wangnan0 at huawei.com>
> Subject: [PATCH 0/4] Replace lseek..write/read to pwrite/pread
> Date: Sat, 26 Apr 2014 12:07:05 +0800
> > In original code there are many operations read from /write to specific
> > positions of a file. This series of patches replace such patterns to
> > pread/pwrite calls, reduces more than 100 lines of code.
> > 
> I'm now writing pthread support patch set and it will naturally
> include pread/pwrite like this patch set.
> It sounds to me that using pread/pwrite only to reduce lseek code is
> weak in motivation. Is there another visible merit? For example, any
> kind of performance improvement. I guess it's small even if exists
> compared to I/O.

There is no user-visible benefit just from applying the patch, that's

The main benefit is that these pread/pwrite operations are atomic and do
not move the file offset, so all subprocesses (or threads) can share
the same file descriptor. This allows to remove reopen_dump_memory(),
for example.

Anyway, is improving code readability really so weak argument?

Petr T

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