From: Ray Bryant <raybry@sgi.com>
To: Marcelo Tosatti <marcelo.tosatti@cyclades.com>
Cc: Con Kolivas <kernel@kolivas.org>, Andrew Morton <akpm@osdl.org>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
riel@redhat.com, piggin@cyberone.com.au, mbligh@aracnet.com
Subject: Re: swapping and the value of /proc/sys/vm/swappiness
Date: Wed, 08 Sep 2004 10:19:51 -0500 [thread overview]
Message-ID: <413F2317.4050401@sgi.com> (raw)
In-Reply-To: <20040907212051.GC3492@logos.cnet>
Marcelo Tosatti wrote:
> Ray, I see the additional swapouts increase the dd performance for your particular testcase:
>
> on 2.6.6:
> Total I/O Avg Swap min max pg cache min max
> ----------- --------- ------- ------ --------- ------- -------
> 0 242.47 MB/s 0 MB ( 0, 0) 3195 MB ( 3138, 3266)
> 20 256.06 MB/s 0 MB ( 0, 0) 3170 MB ( 3074, 3234)
> 40 267.29 MB/s 0 MB ( 0, 0) 3189 MB ( 3137, 3234)
> 60 289.43 MB/s 666 MB ( 72, 1680) 3847 MB ( 3296, 4817) <----------
>
> So for this one testcase it is being beneficial.
>
True enough, but the general trend is that increasing swapping decreases data
rate. This is even more true for the real applications that we are modelling
with this simple benchmark. In thosec cases, the user has a lot of mapped
data that they then write out using buffered I/O. If the mapped data gets
swapped out, then it may have to be swapped back in to be written out to the
file system. It would be faster to keep the mapped data from being swapped
out at all provided that there is enough page cache space to keep the devices
running at full speed.
(And yes, we've suggested that they mmap() the data files -- but sometimes
this is an ISV's code that it causing the problem and we can't necessarily get
them to update their codes to use the API's we want.)
--
Best Regards,
Ray
-----------------------------------------------
Ray Bryant
512-453-9679 (work) 512-507-7807 (cell)
raybry@sgi.com raybry@austin.rr.com
The box said: "Requires Windows 98 or better",
so I installed Linux.
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prev parent reply other threads:[~2004-09-08 15:19 UTC|newest]
Thread overview: 46+ messages / expand[flat|nested] mbox.gz Atom feed top
2004-09-06 19:11 Ray Bryant
2004-09-06 20:10 ` Andrew Morton
2004-09-06 21:22 ` Ray Bryant
2004-09-06 21:36 ` Andrew Morton
2004-09-06 22:37 ` William Lee Irwin III
2004-09-06 23:51 ` Nick Piggin
2004-09-07 0:31 ` Ray Bryant
2004-09-06 22:48 ` William Lee Irwin III
2004-09-06 23:09 ` Con Kolivas
2004-09-06 23:27 ` Andrew Morton
2004-09-06 23:34 ` Con Kolivas
2004-09-07 0:03 ` Marcelo Tosatti
2004-09-07 1:34 ` Con Kolivas
2004-09-07 10:38 ` Nick Piggin
2004-09-07 10:56 ` Con Kolivas
2004-09-08 16:45 ` Marcelo Tosatti
2004-09-09 1:12 ` Con Kolivas
2004-09-07 17:03 ` Ray Bryant
2004-09-07 21:20 ` Marcelo Tosatti
2004-09-08 2:18 ` Marcelo Tosatti
2004-09-08 14:20 ` Ray Bryant
2004-09-08 16:54 ` Marcelo Tosatti
2004-09-08 19:35 ` Ray Bryant
2004-09-08 19:30 ` Marcelo Tosatti
2004-09-09 3:06 ` Ray Bryant
2004-09-09 2:14 ` Marcelo Tosatti
2004-09-09 14:21 ` Ray Bryant
2004-09-09 3:09 ` William Lee Irwin III
2004-09-09 14:16 ` Ray Bryant
2004-09-09 17:23 ` William Lee Irwin III
2004-09-28 1:54 ` Ray Bryant
2004-09-28 3:36 ` Nick Piggin
2004-09-29 0:36 ` Nick Piggin
2004-09-29 4:23 ` Ray Bryant
2004-09-30 17:15 ` Ray Bryant
2004-09-08 17:31 ` Martin J. Bligh
2004-09-08 18:04 ` Rik van Riel
2004-09-08 19:50 ` Diego Calleja
2004-09-08 21:10 ` Martin J. Bligh
2004-09-08 21:55 ` Diego Calleja
2004-09-08 22:20 ` Martin J. Bligh
2004-09-08 23:22 ` Rik van Riel
2004-09-08 22:28 ` Alan Cox
2004-09-08 23:42 ` Martin J. Bligh
2004-09-08 19:54 ` Ray Bryant
2004-09-08 15:19 ` Ray Bryant [this message]
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