From: Jensen <shencanquan@huawei.com>
To: ocfs2-devel@oss.oracle.com
Subject: [Ocfs2-devel] [patch 09/11] ocfs2: llseek requires ocfs2 inode lock for the file in SEEK_END
Date: Tue, 11 Feb 2014 11:35:18 +0800 [thread overview]
Message-ID: <52F99A76.1090103@huawei.com> (raw)
In-Reply-To: <20140210155701.7b1bacb165ca4f89ef46b5ef@linux-foundation.org>
On 2014/2/11 7:57, Andrew Morton wrote:
> On Mon, 10 Feb 2014 16:51:32 +0800 Jensen <shencanquan@huawei.com> wrote:
>
>>>> ocfs2 is a cluster file system. as like read/write/open/rmdir/unlink interface which think of cluster-aware. I think the seek interface need
>>>> cluster-aware. May be it has the performance impact. but it's correctness is more important than performance.
>>> That doesn't mean we can't or shouldn't quantify the performance impact of your patch.
>>>
>>> Please help us measure what the end-user impact of this change will be.
>>> --Mark
>> test result: 1000000 times lseek call;
>> index lseek with inode lock (unit:us) lseek without inode lock (unit:us)
>> 1 1168162 555383
>> 2 1168011 549504
>> 3 1170538 549396
>> 4 1170375 551685
>> 5 1170444 556719
>> 6 1174364 555307
>> 7 1163294 551552
>> 8 1170080 549350
>> 9 1162464 553700
>> 10 1165441 552594
>>
>> avg 1168317 552519
>>
>> avg with lock - avg without lock = 615798
>> (avg with lock - avg without lock)/1000000=0.615798 us
> hm, what does that actually mean. I guess that to get a feel for the
> impact on real workloads, this latency needs to be compared with the
> time for a small IO on fast hardware.
>
> One could test that by creating a large file then doing lots of
> "lseek(random)+read" operations. Which requires forgetting about
> the existence of pread() ;)
>
> .
because lseek only lock in SEEK_END. so your above mention can't test.
>
next prev parent reply other threads:[~2014-02-11 3:35 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-01-24 20:47 [Ocfs2-devel] [patch 09/11] ocfs2: llseek requires ocfs2 inode lock for the file in SEEK_END akpm at linux-foundation.org
2014-02-06 23:42 ` Mark Fasheh
2014-02-06 23:50 ` Andrew Morton
2014-02-06 23:53 ` Andrew Morton
2014-02-07 22:44 ` Mark Fasheh
2014-02-08 1:26 ` Jensen
2014-02-08 2:07 ` Mark Fasheh
2014-02-08 2:46 ` Jensen
2014-02-10 8:51 ` Jensen
2014-02-10 23:57 ` Andrew Morton
2014-02-11 3:35 ` Jensen [this message]
2014-02-08 2:24 ` Jeff Liu
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