From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1751033Ab0CAJ47 (ORCPT ); Mon, 1 Mar 2010 04:56:59 -0500 Received: from 0122700014.0.fullrate.dk ([95.166.99.235]:55056 "EHLO kernel.dk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750804Ab0CAJ46 (ORCPT ); Mon, 1 Mar 2010 04:56:58 -0500 Date: Mon, 1 Mar 2010 10:56:56 +0100 From: Jens Axboe To: Richard Kennedy Cc: lkml Subject: Re: [PATCH] block: don't access jiffies when initialising io_context Message-ID: <20100301095656.GV5768@kernel.dk> References: <1267437213.2127.18.camel@localhost> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <1267437213.2127.18.camel@localhost> Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Mar 01 2010, Richard Kennedy wrote: > As the comment says the initial value of last_waited is never used, so > there is no need to initialise it with the current jiffies. Jiffies is > hot enough without accessing it for no reason. Applied, though it will not make a huge difference in any way. alloc_io_context() only gets called the first time a process does IO, so it's not a hot path. > > Signed-off-by: Richard Kennedy > --- > patch against 2.6.33 > compiled & tested on x86_64 > > diff --git a/block/blk-ioc.c b/block/blk-ioc.c > index 98e6bf6..3f65c8a 100644 > --- a/block/blk-ioc.c > +++ b/block/blk-ioc.c > @@ -91,7 +91,7 @@ struct io_context *alloc_io_context(gfp_t gfp_flags, int node) > spin_lock_init(&ret->lock); > ret->ioprio_changed = 0; > ret->ioprio = 0; > - ret->last_waited = jiffies; /* doesn't matter... */ > + ret->last_waited = 0; /* doesn't matter... */ > ret->nr_batch_requests = 0; /* because this is 0 */ > INIT_RADIX_TREE(&ret->radix_root, GFP_ATOMIC | __GFP_HIGH); > INIT_HLIST_HEAD(&ret->cic_list); > > -- Jens Axboe