From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mukul Kotwani Subject: Re: Max IO size Date: Thu, 1 Aug 2002 23:55:48 -0700 (PDT) Sender: linux-scsi-owner@vger.kernel.org Message-ID: <20020802065548.87405.qmail@web14006.mail.yahoo.com> References: <20020802064403.GG1512@suse.de> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Return-path: In-Reply-To: <20020802064403.GG1512@suse.de> List-Id: linux-scsi@vger.kernel.org To: Jens Axboe Cc: linux-scsi@vger.kernel.org Hello! Thanks again! If that is the case, then with my settings, is there any other reason 512k requests are being broken down into multiple 64k ones? Thanks! Mukul --- Jens Axboe wrote: > On Thu, Aug 01 2002, Mukul Kotwani wrote: > > > > Thanks for the reply! > > > > All my values are set high. The sg_tablesize value > is > > set to 249, max_sectors set to 1024, and I dont > think > > there is any other value which affects IO size as > > such. I didnt see anything called max segment > size/max > > size in the host template. Any other things I am > > missing? > > The max segment size is a property of the queue > associated with the SCSI > devices, it's in fact not directly controllable by > the low level driver > in the 2.4 kernels. What you can set in this regard > is 'use_clustering'. > With that set, the mid layer will attempt to merge > contigious pages into > the same scatter gather segment. This usually only > provides a benefit > with 1kb transfers (since they will typically be > submitted in multiples > anyway from the same page, thus it's easy to cluster > them), with eg 4kb > transfer sizes the amount of clustering that will > happen is neglible. > > -- > Jens Axboe > > - > To unsubscribe from this list: send the line > "unsubscribe linux-scsi" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html __________________________________________________ Do You Yahoo!? Yahoo! Health - Feel better, live better http://health.yahoo.com