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=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,USER_AGENT_SANE_1 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 AAA2AC76191 for ; Sun, 21 Jul 2019 21:09:01 +0000 (UTC) Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by mail.kernel.org (Postfix) with ESMTPS id 77D562085A for ; Sun, 21 Jul 2019 21:09:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="R809rQlK" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 77D562085A 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-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20170209; h=Sender: Content-Transfer-Encoding:Content-Type:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:In-Reply-To:MIME-Version:References: Message-ID:Subject:To:From:Date:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=yfeBksSqtrZyAVOr82DISd8+QGXBOv9sMfG26VftZDU=; b=R809rQlK8gPLAe st+HNGx0Vy37Wbn5tV/KPiITBHRCsuTs2peEntvW+PP6eOWj9QxyCjgwoKl+BhrFLrbfjLkCosuCd 1hzN5g8uIbH1ruE5EIXBYvPizznOVvE+UIu6rUu23Y03UfUu00V+EnGB+N/tn3lhXnQAC2CwGczP3 2VvNjN9S1+LLb5HRoWk75Z8LKMr7qDuvBOoWC+hrXGj1HmLC41dKVjBghtGYKZJy0UTHD+1sBDgFT pFOx9Z7aLC20eue1S3+fw5OO8QEgv4bsPdWyL643kBe1xfx6xUnyIMmOc7/7pcEOH7YZ7DoAzrbJK 6A7YSeAK+zpOVnX32Bvw==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.92 #3 (Red Hat Linux)) id 1hpJ4X-000329-QD; Sun, 21 Jul 2019 21:08:45 +0000 Received: from willy by bombadil.infradead.org with local (Exim 4.92 #3 (Red Hat Linux)) id 1hpJ4P-00031q-HE; Sun, 21 Jul 2019 21:08:37 +0000 Date: Sun, 21 Jul 2019 14:08:37 -0700 From: Matthew Wilcox To: "Paul E. McKenney" Subject: Re: RFC: call_rcu_outstanding (was Re: WARNING in __mmdrop) Message-ID: <20190721210837.GC363@bombadil.infradead.org> References: <0000000000008dd6bb058e006938@google.com> <000000000000964b0d058e1a0483@google.com> <20190721044615-mutt-send-email-mst@kernel.org> <20190721081933-mutt-send-email-mst@kernel.org> <20190721131725.GR14271@linux.ibm.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <20190721131725.GR14271@linux.ibm.com> User-Agent: Mutt/1.11.4 (2019-03-13) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: mhocko@suse.com, "Michael S. Tsirkin" , peterz@infradead.org, jasowang@redhat.com, ldv@altlinux.org, james.bottomley@hansenpartnership.com, linux-mm@kvack.org, namit@vmware.com, mingo@kernel.org, elena.reshetova@intel.com, aarcange@redhat.com, davem@davemloft.net, hch@infradead.org, linux-arm-kernel@lists.infradead.org, keescook@chromium.org, syzkaller-bugs@googlegroups.com, jglisse@redhat.com, viro@zeniv.linux.org.uk, christian@brauner.io, wad@chromium.org, linux-parisc@vger.kernel.org, linux-kernel@vger.kernel.org, luto@amacapital.net, ebiederm@xmission.com, akpm@linux-foundation.org, guro@fb.com Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org On Sun, Jul 21, 2019 at 06:17:25AM -0700, Paul E. McKenney wrote: > Also, the overhead is important. For example, as far as I know, > current RCU gracefully handles close(open(...)) in a tight userspace > loop. But there might be trouble due to tight userspace loops around > lighter-weight operations. I thought you believed that RCU was antifragile, in that it would scale better as it was used more heavily? Would it make sense to have call_rcu() check to see if there are many outstanding requests on this CPU and if so process them before returning? That would ensure that frequent callers usually ended up doing their own processing. _______________________________________________ linux-arm-kernel mailing list linux-arm-kernel@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-arm-kernel