From mboxrd@z Thu Jan 1 00:00:00 1970 From: Ofer Heifetz Subject: RE: Splice status Date: Tue, 13 Jul 2010 15:42:25 +0300 Message-ID: References: <1278334254.2877.158.camel@edumazet-laptop> <1278388580.2466.305.camel@edumazet-laptop> Mime-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: QUOTED-PRINTABLE Cc: Eric Dumazet , Jens Axboe , "netdev@vger.kernel.org" To: Changli Gao Return-path: Received: from galiil.marvell.com ([199.203.130.254]:51302 "EHLO galiil.marvell.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755900Ab0GMMnr convert rfc822-to-8bit (ORCPT ); Tue, 13 Jul 2010 08:43:47 -0400 In-Reply-To: Content-Language: en-US Sender: netdev-owner@vger.kernel.org List-ID: Write and re-write numbers are in MBps. Iozone performs re-write meaning reads a chunk of data and writes it ba= ck, so basically the performance for this operation should be quiet hig= h since kernel caches usage. I forgot to mention that I used EXT4 fs. -Ofer -----Original Message----- =46rom: Changli Gao [mailto:xiaosuo@gmail.com]=20 Sent: Tuesday, July 13, 2010 3:32 PM To: Ofer Heifetz Cc: Eric Dumazet; Jens Axboe; netdev@vger.kernel.org Subject: Re: Splice status On Tue, Jul 13, 2010 at 7:41 PM, Ofer Heifetz wrote= : > Hi, > > I wanted to let you know that I have been testing Samba splice on Mar= vell 6282 SoC on 2.6.35_rc3 and noticed that it gave worst performance = than not using it and also noticed that on re-writing file the iowait i= s high. > > iometer using 2G file (file is created before test) > > Splice =A0write cpu% iow% > ----------------------- > =A0No =A0 =A0 58 =A0 =A098 =A0 =A00 > Yes =A0 =A0 14 =A0 100 =A0 48 > > iozone using 2G file (file created during test) > > Splice =A0write cpu% iow% =A0re-write cpu% iow% > ------------------------------------------- > =A0No =A0 =A0 35 =A0 =A085 =A0 =A04 =A0 =A058.2 =A0 =A0 70 =A0 =A00 > Yes =A0 =A0 33 =A0 =A085 =A0 =A04 =A0 =A015.7 =A0 =A0100 =A0 58 > > Any clue why splice introduces a high iowait? > I noticed samba uses up to 16K per splice syscall, changing the samba= to try more did not help, so I guess it is a kernel limitation. > > -Ofer > What does the column write means? And what do you mean by saying re-write? Thanks. --=20 Regards, Changli Gao(xiaosuo@gmail.com)