From: Linda Walsh <xfs@tlinx.org>
To: Zheng Da <zhengda1936@gmail.com>, Linux-Xfs <linux-xfs@oss.sgi.com>
Subject: Re: concurrent direct IO write in xfs
Date: Fri, 20 Jan 2012 00:53:32 -0800 [thread overview]
Message-ID: <4F192B8C.1050406@tlinx.org> (raw)
In-Reply-To: <CAFLer81XkMTh_gxd95pzxCEs1yGRsTrZijX3c7ewgRzeA7DCSQ@mail.gmail.com>
Zheng Da wrote:
>
> I create a file of 4GB in XFS (the ramdisk has 5GB of space). My test
> program overwrites 4G of data to the file
----
It sounds like you are asking why multiple threads don't
move memory from one point to another point in memory at a faster rate
than one thread alone.
I.e. if you had 2 processes doing an assembly instruction, memmov to move
a chunk of memory from 1 area to another, would you expect to do the move
any faster if you had 2 processors doing the move vs. 1??
I think the limiting factor (unless you have a slow processor and some
REALLY fast memory, but stock x86-64 parts, today have memory running about
2-4 times slower than the processor -- so the memory is usually the bottleneck.
Two processes wouldn't do it any faster, and might actually do it slower due to
resource contention issues -- I would *think*... but I really don't know the
details of how writing from mem2mem and having the target be in the format of
and xfs file system, would cause cpu-bound delays that would be significant to
change the fact that m2m operations are usually mem-bandwidth limited...?
(I don't know the answers, just clarifying what you are asking)...
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next prev parent reply other threads:[~2012-01-20 8:53 UTC|newest]
Thread overview: 19+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-16 0:01 concurrent direct IO write in xfs Zheng Da
2012-01-16 17:48 ` Christoph Hellwig
2012-01-16 19:44 ` Zheng Da
2012-01-16 23:25 ` Dave Chinner
2012-01-17 19:19 ` Zheng Da
2012-01-20 8:53 ` Linda Walsh [this message]
2012-01-20 15:07 ` Zheng Da
2012-01-23 5:11 ` Dave Chinner
2012-01-23 19:34 ` Zheng Da
2012-01-23 20:51 ` Zheng Da
2012-01-24 0:34 ` Stan Hoeppner
2012-01-24 1:40 ` Zheng Da
2012-01-24 3:54 ` Dave Chinner
2012-01-25 21:20 ` Zheng Da
2012-01-25 22:25 ` Dave Chinner
2012-02-09 6:09 ` Dave Chinner
2012-02-09 6:44 ` Zheng Da
2012-02-13 17:48 ` Christoph Hellwig
2012-02-13 23:07 ` Dave Chinner
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