From: Vivek Goyal <vgoyal@redhat.com>
To: Shaohua Li <shaohua.li@intel.com>
Cc: lkml <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <axboe@kernel.dk>,
Herbert Poetzl <herbert@13thfloor.at>,
Eric Dumazet <eric.dumazet@gmail.com>,
Wu Fengguang <wfg@linux.intel.com>
Subject: Re: [PATCH] fix readahead pipeline break caused by block plug
Date: Tue, 31 Jan 2012 09:47:34 -0500 [thread overview]
Message-ID: <20120131144734.GA4378@redhat.com> (raw)
In-Reply-To: <1327996780.21268.42.camel@sli10-conroe>
On Tue, Jan 31, 2012 at 03:59:40PM +0800, Shaohua Li wrote:
> Herbert Poetzl reported a performance regression since 2.6.39. The test
> is a simple dd read, but with big block size. The reason is:
>
> T1: ra (A, A+128k), (A+128k, A+256k)
> T2: lock_page for page A, submit the 256k
> T3: hit page A+128K, ra (A+256k, A+384). the range isn't submitted
> because of plug and there isn't any lock_page till we hit page A+256k
> because all pages from A to A+256k is in memory
> T4: hit page A+256k, ra (A+384, A+ 512). Because of plug, the range isn't
> submitted again.
Why IO is not submitted because of plug? Doesn't task now get scheduled
out causing an unplug? IOW, are we now busy waiting somewhere preventing
unplug?
Thanks
Vivek
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WARNING: multiple messages have this Message-ID (diff)
From: Vivek Goyal <vgoyal@redhat.com>
To: Shaohua Li <shaohua.li@intel.com>
Cc: lkml <linux-kernel@vger.kernel.org>,
linux-mm <linux-mm@kvack.org>,
Andrew Morton <akpm@linux-foundation.org>,
Jens Axboe <axboe@kernel.dk>,
Herbert Poetzl <herbert@13thfloor.at>,
Eric Dumazet <eric.dumazet@gmail.com>,
Wu Fengguang <wfg@linux.intel.com>
Subject: Re: [PATCH] fix readahead pipeline break caused by block plug
Date: Tue, 31 Jan 2012 09:47:34 -0500 [thread overview]
Message-ID: <20120131144734.GA4378@redhat.com> (raw)
In-Reply-To: <1327996780.21268.42.camel@sli10-conroe>
On Tue, Jan 31, 2012 at 03:59:40PM +0800, Shaohua Li wrote:
> Herbert Poetzl reported a performance regression since 2.6.39. The test
> is a simple dd read, but with big block size. The reason is:
>
> T1: ra (A, A+128k), (A+128k, A+256k)
> T2: lock_page for page A, submit the 256k
> T3: hit page A+128K, ra (A+256k, A+384). the range isn't submitted
> because of plug and there isn't any lock_page till we hit page A+256k
> because all pages from A to A+256k is in memory
> T4: hit page A+256k, ra (A+384, A+ 512). Because of plug, the range isn't
> submitted again.
Why IO is not submitted because of plug? Doesn't task now get scheduled
out causing an unplug? IOW, are we now busy waiting somewhere preventing
unplug?
Thanks
Vivek
next prev parent reply other threads:[~2012-01-31 14:47 UTC|newest]
Thread overview: 56+ messages / expand[flat|nested] mbox.gz Atom feed top
2012-01-31 7:59 [PATCH] fix readahead pipeline break caused by block plug Shaohua Li
2012-01-31 7:59 ` Shaohua Li
2012-01-31 8:36 ` Christoph Hellwig
2012-01-31 8:36 ` Christoph Hellwig
2012-01-31 8:48 ` Eric Dumazet
2012-01-31 8:48 ` Eric Dumazet
2012-01-31 8:50 ` Herbert Poetzl
2012-01-31 8:50 ` Herbert Poetzl
2012-01-31 8:53 ` Shaohua Li
2012-01-31 8:53 ` Shaohua Li
2012-01-31 9:17 ` Eric Dumazet
2012-01-31 9:17 ` Eric Dumazet
2012-01-31 10:20 ` Wu Fengguang
2012-01-31 10:20 ` Wu Fengguang
2012-01-31 10:34 ` Wu Fengguang
2012-01-31 10:34 ` Wu Fengguang
2012-01-31 10:46 ` Christoph Hellwig
2012-01-31 10:46 ` Christoph Hellwig
2012-01-31 10:57 ` Wu Fengguang
2012-01-31 10:57 ` Wu Fengguang
2012-01-31 11:34 ` Christoph Hellwig
2012-01-31 11:34 ` Christoph Hellwig
2012-01-31 11:42 ` Wu Fengguang
2012-01-31 11:42 ` Wu Fengguang
2012-01-31 11:57 ` Christoph Hellwig
2012-01-31 11:57 ` Christoph Hellwig
2012-01-31 12:20 ` Wu Fengguang
2012-01-31 12:20 ` Wu Fengguang
2012-02-01 2:25 ` Shaohua Li
2012-02-01 2:25 ` Shaohua Li
2012-01-31 14:47 ` Vivek Goyal [this message]
2012-01-31 14:47 ` Vivek Goyal
2012-01-31 20:23 ` Vivek Goyal
2012-01-31 20:23 ` Vivek Goyal
2012-01-31 22:03 ` Vivek Goyal
2012-01-31 22:03 ` Vivek Goyal
2012-01-31 22:13 ` Andrew Morton
2012-01-31 22:13 ` Andrew Morton
2012-01-31 22:22 ` Vivek Goyal
2012-01-31 22:22 ` Vivek Goyal
2012-02-01 3:36 ` Vivek Goyal
2012-02-01 3:36 ` Vivek Goyal
2012-02-01 7:10 ` Wu Fengguang
2012-02-01 7:10 ` Wu Fengguang
2012-02-01 16:01 ` Vivek Goyal
2012-02-01 16:01 ` Vivek Goyal
2012-02-01 9:18 ` Christoph Hellwig
2012-02-01 9:18 ` Christoph Hellwig
2012-02-01 20:10 ` Vivek Goyal
2012-02-01 20:10 ` Vivek Goyal
2012-02-01 20:13 ` Jeff Moyer
2012-02-01 20:13 ` Jeff Moyer
2012-02-01 20:22 ` Andrew Morton
2012-02-01 20:22 ` Andrew Morton
2012-02-01 7:02 ` Wu Fengguang
2012-02-01 7:02 ` Wu Fengguang
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