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=-2.2 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS,URIBL_BLOCKED,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 B0A07C43144 for ; Fri, 22 Jun 2018 20:03:09 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 73D272485A for ; Fri, 22 Jun 2018 20:03:09 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 73D272485A Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ZenIV.linux.org.uk Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1754129AbeFVUDG (ORCPT ); Fri, 22 Jun 2018 16:03:06 -0400 Received: from zeniv.linux.org.uk ([195.92.253.2]:44948 "EHLO ZenIV.linux.org.uk" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1751370AbeFVUDF (ORCPT ); Fri, 22 Jun 2018 16:03:05 -0400 Received: from viro by ZenIV.linux.org.uk with local (Exim 4.87 #1 (Red Hat Linux)) id 1fWSGl-0000tk-8B; Fri, 22 Jun 2018 20:02:55 +0000 Date: Fri, 22 Jun 2018 21:02:55 +0100 From: Al Viro To: Christoph Hellwig Cc: kernel test robot , Greg Kroah-Hartman , "Darrick J. Wong" , LKML , Linus Torvalds , lkp@01.org Subject: Re: [lkp-robot] [fs] 3deb642f0d: will-it-scale.per_process_ops -8.8% regression Message-ID: <20180622200255.GB30522@ZenIV.linux.org.uk> References: <20180622082752.GX11011@yexl-desktop> <20180622150251.GA12802@lst.de> <20180622151409.GA30522@ZenIV.linux.org.uk> <20180622152850.GA14366@lst.de> <20180622161802.GA18957@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20180622161802.GA18957@lst.de> User-Agent: Mutt/1.9.1 (2017-09-22) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Fri, Jun 22, 2018 at 06:18:02PM +0200, Christoph Hellwig wrote: > On Fri, Jun 22, 2018 at 05:28:50PM +0200, Christoph Hellwig wrote: > > On Fri, Jun 22, 2018 at 04:14:09PM +0100, Al Viro wrote: > > > > http://git.infradead.org/users/hch/vfs.git/shortlog/refs/heads/remove-get-poll-head > > > > > > See objections upthread re "fs,net: move poll busy loop handling into a > > > separate method"; as for the next one... I'd like an ACK from networking > > > folks. The rest of queue makes sense. > > > > I want to see basic results first before micro-optimizing. After that > > I'll send it out to the net folks for feedback. > > I looked into this a bit, in the end sk_can_busy_loop does this: > > return sk->sk_ll_usec && !signal_pending(current); > > where sk_ll_usec defaults based on a sysctl that needs to be > turned on, but can be overriden per socket. > > While at the same time corect poll code already checks net_busy_loop_on > to set POLL_BUSY_LOOP. So except for sockets where people set the > timeout to 0 the code already does the right thing as-is. IMHO not > really worth wasting a FMODE_* flag for it, but if you insist I'll add > it. It's not just that - there's also an issue of extra indirect call on the fast path for sockets. You get this method of yours + ->poll_mask(), which hits another indirect to per-family ->poll_mask(). It might be better to have these combined, sparing us an extra indirect call. Just give it the same calling conventions as ->poll_mask() have...