linux-kernel - Re: fio rand read/write regression with 2.6.32-rc3

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Message-ID: <4e5e476b0910110123s54debc6as435c9cc0d5e8340c@mail.gmail.com>
Date:	Sun, 11 Oct 2009 10:23:09 +0200
From:	Corrado Zoccolo <czoccolo@...il.com>
To:	"Zhang, Yanmin" <yanmin_zhang@...ux.intel.com>
Cc:	Jens Axboe <jens.axboe@...cle.com>,
	LKML <linux-kernel@...r.kernel.org>,
	Linus Torvalds <torvalds@...ux-foundation.org>
Subject: Re: fio rand read/write regression with 2.6.32-rc3

On Sat, Oct 10, 2009 at 11:52 AM, Zhang, Yanmin
<yanmin_zhang@...ux.intel.com> wrote:
> On Sat, 2009-10-10 at 10:01 +0200, Jens Axboe wrote:
>> On Sat, Oct 10 2009, Zhang, Yanmin wrote:
>> > Comparing with 2.6.23-rc1's result, fio rand read write has regression
>> > on my 2*4 core stoakley machine (8GB memory) with a JBOD of 12 disks.
>> >
>> > Every disk has 8 1-GB files. Start 8 sub-processes per disk and every
>> > process random chooses a file on the disk to do 36 times of file read or
>> > write on the file and then choose another file.
>> >
>> >
>> > fio_mmap_rand_read_4k regresion is about 35%.
>>
>> Heh, I seem to recollect I told Linus that this would cost is 30-40%
>> performance. So not totally crazy.
>>
>> So yes, this isn't hugely unexpected. If you send me your fio job files,
>> I'll try and see what I can do about it.
> See the attachment.
>
Hi Yanmin,
the fio test you sent just performs random read, no write seems involved here.
I suspect that you should be able to observe the same regression if
you just run on a single disk. Can you confirm?
Is your disk a SATA2 rotational disk with NCQ?

Thanks,
Corrado

-- 
__________________________________________________________________________

dott. Corrado Zoccolo                          mailto:czoccolo@...il.com
PhD - Department of Computer Science - University of Pisa, Italy
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