linux-kernel - Re: [patch 0/7] Add TRIM support for raid linear/0/1/10

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Message-ID: <alpine.LRH.2.02.1203150857190.4562@diagnostix.dwd.de>
Date:	Thu, 15 Mar 2012 09:08:07 +0000 (GMT)
From:	Holger Kiehl <Holger.Kiehl@....de>
To:	Shaohua Li <shli@...nel.org>
cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	"linux-raid@...r.kernel.org" <linux-raid@...r.kernel.org>,
	"neilb@...e.de" <neilb@...e.de>,
	"axboe@...nel.dk" <axboe@...nel.dk>
Subject: Re: [patch 0/7] Add TRIM support for raid linear/0/1/10

On Thu, 15 Mar 2012, Shaohua Li wrote:

> 2012/3/15 Holger Kiehl <Holger.Kiehl@....de>:
>> On Wed, 14 Mar 2012, Shaohua Li wrote:
>>
>>> Maybe the discard runs slow with small size request in the disk.
>>> please drop patch "blk: add plug for blkdev_issue_discard" and try again.
>>> Since
>>> we can't do merge, the plug just introduces latency.
>>>
>> Tried again without the patch applied, but there is only a very small
>> performance increase (520->600 agains 4000 fps without discard).
>>
>> The benchmark creates lots of small files (2 KiB) and deletes them again.
>>
>>
>>> if it doesn't help, please capture a blktrace when you do the benchmark
>>> and
>>> send it to me.
>>>
>> Ok, I will do this tomorrow. Need some sleep :-)
>>
>> Thanks for your work on supporting discard in MD!
> I tried your benchmark, create 2000k 2k files and delete them and
> follows a sync.
> the discard runs pretty fast for both raid 0/1. So can't reproduce the
> issue. I'm using
> a fusionio card though. I'm afraid nothing I can do till get you blktrace.
>
The blktrace is a bit large so I have uploaded it to:

    ftp://ftp.dwd.de/pub/afd/test/trim/trace

This is while the benchmark was running. Just a reminder, md2 is
/home under which the benchmark was running. And md2 is a raid0 of
sda3, sdb3 and sdc3. While md1 is / and also raid0 of ada2, sdb2 and
sdc2.

There is also another blktarce when all files are deleted and note
this is only part of it (10 min), it takes about 30 minutes to delete
all. You can find this here:

    ftp://ftp.dwd.de/pub/afd/test/trim/trace2

Please tell me if you need more information or what else I can do to
help find the problem.

Thanks,
Holger
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