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=-0.6 required=3.0 tests=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE,SPF_PASS autolearn=no 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 25369C33CB2 for ; Fri, 31 Jan 2020 06:35:30 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id EB35D20678 for ; Fri, 31 Jan 2020 06:35:29 +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="PKBfhEHp" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726017AbgAaGf3 (ORCPT ); Fri, 31 Jan 2020 01:35:29 -0500 Received: from bombadil.infradead.org ([198.137.202.133]:53166 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1725815AbgAaGf3 (ORCPT ); Fri, 31 Jan 2020 01:35:29 -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=BW2En7pNvZHFAlYVYPJhv8/Lsw4xkSZ3vMI5gF+lSjk=; b=PKBfhEHpbX4Au31TW/i23h6On d1QKv08tCb/QNV7z3y2HMuppnzJsQFhzzFbwPCcauiX+txiFbnz00NfqbM0Rc9roWmI1FycutUX2g bnHooMO2UvS1UyOQjq+e7q0HQbwdCMB5R6huwhOSBHQTpBC/YS3dWdlcKhr8MlhpAuGhsIlITTBM6 K8NZHsOXFJMonEJFJ1fqaOGzOtipTo7xw2sGIP/zqfifNBz3l/c3DfY3HT18RpCZmG26RdCFSe+I0 dFn8crWyLbl6QhXOn2OePRE8tPGoyHRjRzxBD3K8Dz2VknHIS15efKgaCZITTvsT0IBGmiW+FZ6Ok GLsdkVoug==; Received: from hch by bombadil.infradead.org with local (Exim 4.92.3 #3 (Red Hat Linux)) id 1ixPtn-00076I-Ry; Fri, 31 Jan 2020 06:35:27 +0000 Date: Thu, 30 Jan 2020 22:35:27 -0800 From: Christoph Hellwig To: Jens Axboe Cc: Andrzej Jakowski , song@kernel.org, linux-block@vger.kernel.org, linux-raid@vger.kernel.org, Artur Paszkiewicz Subject: Re: [PATCH 1/2] block: introduce polling on bio level Message-ID: <20200131063527.GC6267@infradead.org> References: <20200126044138.5066-1-andrzej.jakowski@linux.intel.com> <20200126044138.5066-2-andrzej.jakowski@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: 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 Wed, Jan 29, 2020 at 09:01:49PM -0700, Jens Axboe wrote: > blk_poll() used to be a pointer in the queue, but since we just had > one implementation, we got rid of it. Might make sense to > reintroduce that, and just make it an optimized indirect call. I > think that would be prettier than add the bio hack in the middle of > it, and you're having to add a queue pointer anyway. Well, the other reason is to avoid an indirect call for the blk-mq case, which are fairly expensive. In fact I'm pretty sure we avoid indirect calls from the bio layer into blk-mq entirely for the fast path at the moment, and it would be great to keep it that way.