Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756826Ab1EXRek (ORCPT ); Tue, 24 May 2011 13:34:40 -0400 Received: from smtp-out.google.com ([216.239.44.51]:53238 "EHLO smtp-out.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756649Ab1EXRei convert rfc822-to-8bit (ORCPT ); Tue, 24 May 2011 13:34:38 -0400 DomainKey-Signature: a=rsa-sha1; c=nofws; d=google.com; s=beta; h=mime-version:in-reply-to:references:from:date:message-id:subject:to :cc:content-type:content-transfer-encoding; b=FolSxiC6a9JfX7XzwWVbT4O9ItmvyhHqJSkeo7ID1kTCzoxn0E/b4OSixXUJDaWTUk 85tBPNfO0x37gDiCaDwQ== MIME-Version: 1.0 In-Reply-To: <1306207131-2296-2-git-send-email-namhyung@gmail.com> References: <1306207131-2296-1-git-send-email-namhyung@gmail.com> <1306207131-2296-2-git-send-email-namhyung@gmail.com> From: Justin TerAvest Date: Tue, 24 May 2011 10:34:16 -0700 Message-ID: Subject: Re: [PATCH 2/4] cfq-iosched: reduce bit operations in cfq_choose_req() To: Namhyung Kim Cc: Jens Axboe , lkml Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT X-System-Of-Record: true Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1978 Lines: 52 Why make this change? Are we that sensitive to the number of operations? It makes the code a bit harder to read, I think. On Mon, May 23, 2011 at 8:18 PM, Namhyung Kim wrote: > Reduce the number of bit operations in cfq_choose_req() on average > (and worst) cases. > > Signed-off-by: Namhyung Kim > --- > ?block/cfq-iosched.c | ? 14 +++++--------- > ?1 files changed, 5 insertions(+), 9 deletions(-) > > diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c > index 151a050e692c..a79e62063144 100644 > --- a/block/cfq-iosched.c > +++ b/block/cfq-iosched.c > @@ -665,15 +665,11 @@ cfq_choose_req(struct cfq_data *cfqd, struct request *rq1, struct request *rq2, > ? ? ? ?if (rq2 == NULL) > ? ? ? ? ? ? ? ?return rq1; > > - ? ? ? if (rq_is_sync(rq1) && !rq_is_sync(rq2)) > - ? ? ? ? ? ? ? return rq1; > - ? ? ? else if (rq_is_sync(rq2) && !rq_is_sync(rq1)) > - ? ? ? ? ? ? ? return rq2; > - ? ? ? if ((rq1->cmd_flags & REQ_META) && !(rq2->cmd_flags & REQ_META)) > - ? ? ? ? ? ? ? return rq1; > - ? ? ? else if ((rq2->cmd_flags & REQ_META) && > - ? ? ? ? ? ? ? ?!(rq1->cmd_flags & REQ_META)) > - ? ? ? ? ? ? ? return rq2; > + ? ? ? if (rq_is_sync(rq1) != rq_is_sync(rq2)) > + ? ? ? ? ? ? ? return rq_is_sync(rq1) ? rq1 : rq2; > + > + ? ? ? if ((rq1->cmd_flags ^ rq2->cmd_flags) & REQ_META) > + ? ? ? ? ? ? ? return rq1->cmd_flags & REQ_META ? rq1 : rq2; > > ? ? ? ?s1 = blk_rq_pos(rq1); > ? ? ? ?s2 = blk_rq_pos(rq2); > -- > 1.7.5.2 > > -- > 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/ > -- 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/