From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.3 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS,USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 9FC46C43441 for ; Wed, 14 Nov 2018 15:20:54 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 5BF34208E7 for ; Wed, 14 Nov 2018 15:20:54 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (2048-bit key) header.d=infradead.org header.i=@infradead.org header.b="WJjbOvGY" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 5BF34208E7 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=infradead.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-block-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732485AbeKOBYd (ORCPT ); Wed, 14 Nov 2018 20:24:33 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:42920 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1732367AbeKOBYd (ORCPT ); Wed, 14 Nov 2018 20:24:33 -0500 DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20170209; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description:Resent-Date: Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID:List-Id: List-Help:List-Unsubscribe:List-Subscribe:List-Post:List-Owner:List-Archive; bh=xvFVkn1ija1zxEIVFEoSmFcj97qjRat+B5BKyo45XE0=; b=WJjbOvGYAzugwL94IDtZGdidq dpS61CzW3OBsalUHh+b6IpQVPKikqYjuprABLVj8PNeFIT3cCFfbtMF2nJvItQrI9BvaelVCroyAn frqrR70fxdC1bjAl/fHc0xPfGDF+F6CJPBGvApCsYMNZSYUOycWTj2j22HgpcqR7HiFgOtfIDgh95 5Wk6Mdyx3GvisggeQtZUKRPhJxkIU5Xh5bubjYoZj2hrtflYjTyuduJy/K2mqXWJOna9VX3ArUByw jNs9RuSp8V1frz0o+/kSEXwKDHilpfHSbZHh21H6PdV/pBLvkS/2FgLV8X8HEq/nNWZJXM2QPI+6X jlHyEWjhg==; Received: from hch by bombadil.infradead.org with local (Exim 4.90_1 #2 (Red Hat Linux)) id 1gMwyL-00073y-9h; Wed, 14 Nov 2018 15:20:53 +0000 Date: Wed, 14 Nov 2018 07:20:53 -0800 From: Christoph Hellwig To: Jens Axboe Cc: linux-block@vger.kernel.org Subject: Re: [PATCH 3/6] blk-mq: embed blk_mq_ops directly in the request queue Message-ID: <20181114152053.GA22186@infradead.org> References: <20181110151317.3813-1-axboe@kernel.dk> <20181110151317.3813-4-axboe@kernel.dk> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20181110151317.3813-4-axboe@kernel.dk> User-Agent: Mutt/1.9.2 (2017-12-15) X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html Sender: linux-block-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-block@vger.kernel.org On Sat, Nov 10, 2018 at 08:13:14AM -0700, Jens Axboe wrote: > This saves an indirect function call everytime we have to > call one of the strategy functions. We keep it const, and just > hack around that a bit in blk_mq_init_allocated_queue(), which > is where we copy the ops in. What amount of difference does this patch make? This really defeats the whole constification, which doesn't hinge on the const attribute itself, but on having the static ops in a read-only mapped section. So unless it is a real measurable and big enough difference I'm against this patch, and if there is a real an measurable difference we might have to find other ways to archive this goal.