netdev - RE: Splice status

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Message-ID: <EE71107DF0D1F24FA2D95041E64AB9E8ED254E7C17@IL-MB01.marvell.com>
Date:	Tue, 13 Jul 2010 17:40:14 +0300
From:	Ofer Heifetz <oferh@...vell.com>
To:	Changli Gao <xiaosuo@...il.com>
CC:	Eric Dumazet <eric.dumazet@...il.com>,
	Jens Axboe <axboe@...nel.dk>,
	"netdev@...r.kernel.org" <netdev@...r.kernel.org>
Subject: RE: Splice status

I profiled the splice iometer write run and noticed that blk_end_request_err is being called many times, it looks like a good candidate for the high iowait, need to debug the root cause for it.

-Ofer

-----Original Message-----
From: Changli Gao [mailto:xiaosuo@...il.com] 
Sent: Tuesday, July 13, 2010 4:58 PM
To: Ofer Heifetz
Cc: Eric Dumazet; Jens Axboe; netdev@...r.kernel.org
Subject: Re: Splice status

On Tue, Jul 13, 2010 at 8:42 PM, Ofer Heifetz <oferh@...vell.com> wrote:
> Write and re-write numbers are in MBps.
> Iozone performs re-write meaning reads a chunk of data and writes it back, so basically the performance for this operation should be quiet high since kernel caches usage.
>
> I forgot to mention that I used EXT4 fs.

Maybe it is caused by this line in generic_file_splice_write():

                balance_dirty_pages_ratelimited_nr(mapping, nr_pages);

Please try to test it again without this line.

-- 
Regards,
Changli Gao(xiaosuo@...il.com)
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