From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vladislav Bolkhovitin Subject: Re: [Scst-devel] Re: Ang: Re: [Stgt-devel] Re: [Iscsitarget-devel] stgt a new version of iscsi target? Date: Wed, 14 Dec 2005 18:17:07 +0300 Message-ID: <43A03773.1070704@vlnb.net> References: <4399A2BA.1070505@vlnb.net> <20051210174658I.fujita.tomonori@lab.ntt.co.jp> <439AF51E.1080509@vlnb.net> <200512101554.jBAFsf7v025451@r-dd.iij4u.or.jp> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <200512101554.jBAFsf7v025451@r-dd.iij4u.or.jp> Sender: iscsitarget-devel-admin@lists.sourceforge.net Errors-To: iscsitarget-devel-admin@lists.sourceforge.net List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , List-Archive: To: FUJITA Tomonori Cc: michaelc@cs.wisc.edu, johan@capvert.se, iscsitarget-devel@lists.sourceforge.net, mingz@ele.uri.edu, stgt-devel@lists.berlios.de, WRWHITEHEAD@novell.com, scst-devel@lists.sourceforge.net, linux-scsi@vger.kernel.org, hch@infradead.org List-Id: linux-scsi@vger.kernel.org FUJITA Tomonori wrote: > From: Vladislav Bolkhovitin > Subject: Re: Ang: Re: [Stgt-devel] Re: [Iscsitarget-devel] stgt a new version of iscsi target? > Date: Sat, 10 Dec 2005 18:32:46 +0300 > > >>>>>Also is the page cache comment in reference to us using the page cache >>>>>for our reads and writes or I am not sure why you wrote that if you do >>>>>not do it right now. >>>> >>>>Hm, at first, the page cache already used somehow in fileio dev handler >>>>(though, with additional mem copy). At the second, fully utilize the >>>>page cache is one of two major improvements that are pending in scst, >>>>because it is required changing the kernel, which until some moment try >>>>to avoid. Although I prepared what is necessary for that. >>>> >>>>The idea basically is the following. When READ operation arrives, pages >>>>for all requested blocks are at first searched in the page cache >>>>(probably, in SIRQ context, because it isn't expensive operation) and if >>>>all pages are found, they are referenced and the result will be sent to >>>>the initiator. Then the pages will be dereferenced (so, no pages >>>>allocation will be done at all). Otherwise, the missed pages will be >>>>allocated and the command will be rescheduled to the thread, which will >>>>read them. Then, after the response is sent, the pages will remain in >>>>the page cache for future accesses. For WRITEs the processing is the >>>>similar, the pages with the data will be put in the page cache. >>> >>>The Ardis iSCSI target code does the same thing. >> >>Perfectly. So, why don't do it on the mid-layer level where all targets >>can benefit from it? > > > Because I think that it not of much performance benefit. Are you sure? Why do you think using the cache together with its nice features like read-ahead doesn't bring major performance benefits? Vlad ------------------------------------------------------- This SF.net email is sponsored by: Splunk Inc. Do you grep through log files for problems? Stop! Download the new AJAX search engine that makes searching your log files as easy as surfing the web. DOWNLOAD SPLUNK! http://ads.osdn.com/?ad_id=7637&alloc_id=16865&op=click