Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755350AbZFTO4W (ORCPT ); Sat, 20 Jun 2009 10:56:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754813AbZFTO4J (ORCPT ); Sat, 20 Jun 2009 10:56:09 -0400 Received: from netrider.rowland.org ([192.131.102.5]:47776 "HELO netrider.rowland.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with SMTP id S1753142AbZFTO4G (ORCPT ); Sat, 20 Jun 2009 10:56:06 -0400 Date: Sat, 20 Jun 2009 10:56:09 -0400 (EDT) From: Alan Stern X-X-Sender: stern@netrider.rowland.org To: Ravish Tayal cc: Kernel development list , , SCSI development list , USB list Subject: Re: generic_make_request fucntion for scsi_disk In-Reply-To: Message-ID: MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 826 Lines: 23 You should use Reply-To-All so that other people reading the mailing list will be able to follow and contribute to the thread. On Sat, 20 Jun 2009, Ravish Tayal wrote: > Thanks Alan, > > I am actually trying to profile the time taken by each layer to complete the > disk write opertaion as sys_write to queue_command invokation veries alot. Of course it varies. The kernel buffers disk writes, shuffles them around, and then carries them out when it wants to. As James has pointed out, your write(2) system calls don't directly cause any I/O to take place. Alan Stern -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/