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Message-ID: <e85b9d30805101339je48a55dnd2fbd5601c27a3be@mail.gmail.com>
Date: Sat, 10 May 2008 22:39:50 +0200
From: Matthew <jackdachef@...il.com>
To: "Fabio Checconi" <fabio@...dalf.sssup.it>
Cc: "Linux Kernel Mailing List" <linux-kernel@...r.kernel.org>,
jens.axboe@...cle.com
Subject: Re: performance "regression" in cfq compared to anticipatory, deadline and noop
> Hi, I'm experiencing some cfq/bfq performance issues too, but I'm
> still not able to track down the reasons, so before posting on this
> topic on the mailing list I'd ask you a couple of questions.
>
> 1) Are you running the hdparm performance test under some cpu load?
> (Even two hdparm instances ran in parallel could do.)
>
> 2) Does using a bigger value of slice_idle increase the throughput?
>
Hi,
1) no it was always in (almost) complete idle
2) a bigger value even made it worse, setting it to "0" however
seemingly "fixed" it, I however don't know how the overall
effect/impact is, this will need some more real-world testing ;)
cat /sys/block/sdd/queue/iosched/slice_idle
0
hdparm -t /dev/sdd
/dev/sdd:
Timing buffered disk reads: 314 MB in 3.01 seconds = 104.32 MB/sec
hdparm -t /dev/sdd
/dev/sdd:
Timing buffered disk reads: 312 MB in 3.00 seconds = 103.86 MB/sec
hdparm -t /dev/sdd
/dev/sdd:
Timing buffered disk reads: 314 MB in 3.01 seconds = 104.24 MB/sec
one side-node / question:
will this cause more wakeups on the cpu and/or decrease battery
runtime on, e.g. laptops ?
> Thank you very much, I'll try hdparm on my test boxes and come back
> to the list if I find something on that.
>
> As a sidenote, Ingo is not the author/maintainer of cfq, maybe the
> next time CC: Jens Axboe for that.
>
oops, didn't know that, thanks - didn't want to give the wrong person
the "credits"
hi & kudos to Jens ;)
here's a nice site which explains all of the settings:
http://www.nextre.it/oracledocs/ioscheduler_03.html
Regards
Mat
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