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=-0.8 required=3.0 tests=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 6F2F6C76190 for ; Fri, 26 Jul 2019 11:49:31 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 53949229F3 for ; Fri, 26 Jul 2019 11:49:31 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726714AbfGZLta (ORCPT ); Fri, 26 Jul 2019 07:49:30 -0400 Received: from mail-qt1-f194.google.com ([209.85.160.194]:34703 "EHLO mail-qt1-f194.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726138AbfGZLta (ORCPT ); Fri, 26 Jul 2019 07:49:30 -0400 Received: by mail-qt1-f194.google.com with SMTP id k10so52326729qtq.1 for ; Fri, 26 Jul 2019 04:49:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=i8wjsn/J7AjCMbxusJs+A5ywmyPLK0X8wVGP+ZIy8uY=; b=TiKJgGZB7IRJ9rL7P4MUfr6lTBassWJZAuXAJNwXxX4+HXlcCvG/+L3jw2zG3oe9q7 l/CK9/1N+OkQsUj9/qVRmElRwRu57GQFyDgnouoSH5JkRB9LSUK/zWEaso4p8dXBDrNx Vq3SoULGlYwmBHgDvrKVtWamjt/yQNDHIq9c8lybDuzhMSJG0+Dvo4NF61+8mTDgP1tB YWOYtuNzpJ8yyR/9/EupVP/aOOTtdRrUzr8ESNOkvD1fvJDrNqv/A+m6crjwEk9cAPu4 L210Qvscv2jjmhTGuzPj+BRLZEL6bw/ovQLCPyYlW76CZel29y3WHvQ0TzQiY5Au6jZV 8juQ== X-Gm-Message-State: APjAAAWbwuttGPNpwWPACDhDmIurtwdY/mM8MQ2cTKEYF4dC11MqsLwP R8dyyRrKX/LAP9OVR36SPxRsJQ== X-Google-Smtp-Source: APXvYqwMsTGjfM7uQAnObrU4lf6ZCQqoJiT3HpWwMpyDoRsBS/oRMj++843f20ueHHr8c24KKPsFiw== X-Received: by 2002:ac8:32e8:: with SMTP id a37mr66953459qtb.231.1564141769219; Fri, 26 Jul 2019 04:49:29 -0700 (PDT) Received: from redhat.com ([212.92.104.165]) by smtp.gmail.com with ESMTPSA id f14sm21725527qto.11.2019.07.26.04.49.22 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 26 Jul 2019 04:49:28 -0700 (PDT) Date: Fri, 26 Jul 2019 07:49:19 -0400 From: "Michael S. Tsirkin" To: Jason Wang Cc: syzbot , aarcange@redhat.com, akpm@linux-foundation.org, christian@brauner.io, davem@davemloft.net, ebiederm@xmission.com, elena.reshetova@intel.com, guro@fb.com, hch@infradead.org, james.bottomley@hansenpartnership.com, jglisse@redhat.com, keescook@chromium.org, ldv@altlinux.org, linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, linux-parisc@vger.kernel.org, luto@amacapital.net, mhocko@suse.com, mingo@kernel.org, namit@vmware.com, peterz@infradead.org, syzkaller-bugs@googlegroups.com, viro@zeniv.linux.org.uk, wad@chromium.org Subject: Re: WARNING in __mmdrop Message-ID: <20190726074644-mutt-send-email-mst@kernel.org> References: <20190723035725-mutt-send-email-mst@kernel.org> <3f4178f1-0d71-e032-0f1f-802428ceca59@redhat.com> <20190723051828-mutt-send-email-mst@kernel.org> <20190725012149-mutt-send-email-mst@kernel.org> <55e8930c-2695-365f-a07b-3ad169654d28@redhat.com> <20190725042651-mutt-send-email-mst@kernel.org> <84bb2e31-0606-adff-cf2a-e1878225a847@redhat.com> <20190725092332-mutt-send-email-mst@kernel.org> <11802a8a-ce41-f427-63d5-b6a4cf96bb3f@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Disposition: inline Content-Transfer-Encoding: 8bit In-Reply-To: <11802a8a-ce41-f427-63d5-b6a4cf96bb3f@redhat.com> Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Thu, Jul 25, 2019 at 10:25:25PM +0800, Jason Wang wrote: > > On 2019/7/25 下午9:26, Michael S. Tsirkin wrote: > > > Exactly, and that's the reason actually I use synchronize_rcu() there. > > > > > > So the concern is still the possible synchronize_expedited()? > > I think synchronize_srcu_expedited. > > > > synchronize_expedited sends lots of IPI and is bad for realtime VMs. > > > > > Can I do this > > > on through another series on top of the incoming V2? > > > > > > Thanks > > > > > The question is this: is this still a gain if we switch to the > > more expensive srcu? If yes then we can keep the feature on, > > > I think we only care about the cost on srcu_read_lock() which looks pretty > tiny form my point of view. Which is basically a READ_ONCE() + WRITE_ONCE(). > > Of course I can benchmark to see the difference. > > > > if not we'll put it off until next release and think > > of better solutions. rcu->srcu is just a find and replace, > > don't see why we need to defer that. can be a separate patch > > for sure, but we need to know how well it works. > > > I think I get here, let me try to do that in V2 and let's see the numbers. > > Thanks There's one other thing that bothers me, and that is that for large rings which are not physically contiguous we don't implement the optimization. For sure, that can wait, but I think eventually we should vmap large rings. -- MST 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=-0.8 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_HELO_NONE, SPF_PASS,URIBL_BLOCKED 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 C1D86C7618B for ; Fri, 26 Jul 2019 11:49:36 +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 978E2229F3 for ; Fri, 26 Jul 2019 11:49:36 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="mZ9ZAHi2" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 978E2229F3 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=redhat.com 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=OmReHEEVThY0ZOGTbfVFzybSujVwdDfXqM9y+E077P8=; b=mZ9ZAHi2q3dD89 4gFSS//aW0Cw15kqPlh0Gl6cF7kCA3sPry49j70UqbQE5ycUKRdRgWwTKG2RcKFqfCEKVJ1YZJHzu IKTyzg1EwlupIJcyrlvhGjWjQ4odAMpqBf6Vd5nhi13a1aGISWmyMV4My4qTk1n+8M6JUs7DGgeiI d5P2/uvkqWAaqkZKZjd3x29rLtxOywRRj+0Iu8es3o6iVB6AzU4PsFo0ZLyQHGRVeGP45q1918znc XIN8unLOHN9yMIer+3rBLbupyY/ssFr5BXimtDayqYUkEVOA6B8JzivYk/+EOPJAoUB/QRLLAIpO7 jumrzvF1Djby2+blvVVw==; 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 1hqyjA-0004B7-5C; Fri, 26 Jul 2019 11:49:36 +0000 Received: from mail-qt1-f195.google.com ([209.85.160.195]) by bombadil.infradead.org with esmtps (Exim 4.92 #3 (Red Hat Linux)) id 1hqyj6-00049X-9X for linux-arm-kernel@lists.infradead.org; Fri, 26 Jul 2019 11:49:33 +0000 Received: by mail-qt1-f195.google.com with SMTP id h18so52256701qtm.9 for ; Fri, 26 Jul 2019 04:49:29 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:content-transfer-encoding :in-reply-to; bh=i8wjsn/J7AjCMbxusJs+A5ywmyPLK0X8wVGP+ZIy8uY=; b=CZ56iqRUevQNANJ4BHDqi3dU+hJrh5rCnc8WOiX18Tt//lZBDljpwpIZi43YJndhzb TajXWVP5EovyB+fMQcDcocUtgwEmhuLXYNcFOTvXzmsjVd6Ai4WcL6ajuqcMf0AJblHf IX3q1Igi82DjTfehJgUzjzp+SwRaZR//9yB43yP/nJHpk7CsZx7814GI3U+MHQUaUTl2 E1GbvCbjyDb8FuTtJNNQUokIUjh+G9UgNQW0ivOVp+RwV3SOGaDS/jGHGg43ufBdMeYj KQg28uH9EmPpNiZDKcHmDTruzpWA53uwhGKVau47oxIadQdmd0kygOyXeWN2AkZwYx7z gjag== X-Gm-Message-State: APjAAAXDdUtzVE8yc2unohufaOuOxLkFlQ3xtyJjMWyNeL8Z67BO0EuM +uGSBYzd9xKN3wPemqddHI2uGg== X-Google-Smtp-Source: APXvYqwMsTGjfM7uQAnObrU4lf6ZCQqoJiT3HpWwMpyDoRsBS/oRMj++843f20ueHHr8c24KKPsFiw== X-Received: by 2002:ac8:32e8:: with SMTP id a37mr66953459qtb.231.1564141769219; Fri, 26 Jul 2019 04:49:29 -0700 (PDT) Received: from redhat.com ([212.92.104.165]) by smtp.gmail.com with ESMTPSA id f14sm21725527qto.11.2019.07.26.04.49.22 (version=TLS1_3 cipher=AEAD-AES256-GCM-SHA384 bits=256/256); Fri, 26 Jul 2019 04:49:28 -0700 (PDT) Date: Fri, 26 Jul 2019 07:49:19 -0400 From: "Michael S. Tsirkin" To: Jason Wang Subject: Re: WARNING in __mmdrop Message-ID: <20190726074644-mutt-send-email-mst@kernel.org> References: <20190723035725-mutt-send-email-mst@kernel.org> <3f4178f1-0d71-e032-0f1f-802428ceca59@redhat.com> <20190723051828-mutt-send-email-mst@kernel.org> <20190725012149-mutt-send-email-mst@kernel.org> <55e8930c-2695-365f-a07b-3ad169654d28@redhat.com> <20190725042651-mutt-send-email-mst@kernel.org> <84bb2e31-0606-adff-cf2a-e1878225a847@redhat.com> <20190725092332-mutt-send-email-mst@kernel.org> <11802a8a-ce41-f427-63d5-b6a4cf96bb3f@redhat.com> MIME-Version: 1.0 Content-Disposition: inline In-Reply-To: <11802a8a-ce41-f427-63d5-b6a4cf96bb3f@redhat.com> X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190726_044932_329727_19CEC1EB X-CRM114-Status: GOOD ( 16.59 ) 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, peterz@infradead.org, ldv@altlinux.org, james.bottomley@hansenpartnership.com, linux-mm@kvack.org, namit@vmware.com, mingo@kernel.org, elena.reshetova@intel.com, keescook@chromium.org, aarcange@redhat.com, davem@davemloft.net, hch@infradead.org, christian@brauner.io, syzbot , syzkaller-bugs@googlegroups.com, jglisse@redhat.com, viro@zeniv.linux.org.uk, linux-arm-kernel@lists.infradead.org, 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="utf-8" Content-Transfer-Encoding: base64 Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+infradead-linux-arm-kernel=archiver.kernel.org@lists.infradead.org T24gVGh1LCBKdWwgMjUsIDIwMTkgYXQgMTA6MjU6MjVQTSArMDgwMCwgSmFzb24gV2FuZyB3cm90 ZToKPiAKPiBPbiAyMDE5LzcvMjUg5LiL5Y2IOToyNiwgTWljaGFlbCBTLiBUc2lya2luIHdyb3Rl Ogo+ID4gPiBFeGFjdGx5LCBhbmQgdGhhdCdzIHRoZSByZWFzb24gYWN0dWFsbHkgSSB1c2Ugc3lu Y2hyb25pemVfcmN1KCkgdGhlcmUuCj4gPiA+IAo+ID4gPiBTbyB0aGUgY29uY2VybiBpcyBzdGls bCB0aGUgcG9zc2libGUgc3luY2hyb25pemVfZXhwZWRpdGVkKCk/Cj4gPiBJIHRoaW5rIHN5bmNo cm9uaXplX3NyY3VfZXhwZWRpdGVkLgo+ID4gCj4gPiBzeW5jaHJvbml6ZV9leHBlZGl0ZWQgc2Vu ZHMgbG90cyBvZiBJUEkgYW5kIGlzIGJhZCBmb3IgcmVhbHRpbWUgVk1zLgo+ID4gCj4gPiA+IENh biBJIGRvIHRoaXMKPiA+ID4gb24gdGhyb3VnaCBhbm90aGVyIHNlcmllcyBvbiB0b3Agb2YgdGhl IGluY29taW5nIFYyPwo+ID4gPiAKPiA+ID4gVGhhbmtzCj4gPiA+IAo+ID4gVGhlIHF1ZXN0aW9u IGlzIHRoaXM6IGlzIHRoaXMgc3RpbGwgYSBnYWluIGlmIHdlIHN3aXRjaCB0byB0aGUKPiA+IG1v cmUgZXhwZW5zaXZlIHNyY3U/IElmIHllcyB0aGVuIHdlIGNhbiBrZWVwIHRoZSBmZWF0dXJlIG9u LAo+IAo+IAo+IEkgdGhpbmsgd2Ugb25seSBjYXJlIGFib3V0IHRoZSBjb3N0IG9uIHNyY3VfcmVh ZF9sb2NrKCkgd2hpY2ggbG9va3MgcHJldHR5Cj4gdGlueSBmb3JtIG15IHBvaW50IG9mIHZpZXcu IFdoaWNoIGlzIGJhc2ljYWxseSBhIFJFQURfT05DRSgpICsgV1JJVEVfT05DRSgpLgo+IAo+IE9m IGNvdXJzZSBJIGNhbiBiZW5jaG1hcmsgdG8gc2VlIHRoZSBkaWZmZXJlbmNlLgo+IAo+IAo+ID4g aWYgbm90IHdlJ2xsIHB1dCBpdCBvZmYgdW50aWwgbmV4dCByZWxlYXNlIGFuZCB0aGluawo+ID4g b2YgYmV0dGVyIHNvbHV0aW9ucy4gcmN1LT5zcmN1IGlzIGp1c3QgYSBmaW5kIGFuZCByZXBsYWNl LAo+ID4gZG9uJ3Qgc2VlIHdoeSB3ZSBuZWVkIHRvIGRlZmVyIHRoYXQuIGNhbiBiZSBhIHNlcGFy YXRlIHBhdGNoCj4gPiBmb3Igc3VyZSwgYnV0IHdlIG5lZWQgdG8ga25vdyBob3cgd2VsbCBpdCB3 b3Jrcy4KPiAKPiAKPiBJIHRoaW5rIEkgZ2V0IGhlcmUsIGxldCBtZSB0cnkgdG8gZG8gdGhhdCBp biBWMiBhbmQgbGV0J3Mgc2VlIHRoZSBudW1iZXJzLgo+IAo+IFRoYW5rcwoKVGhlcmUncyBvbmUg b3RoZXIgdGhpbmcgdGhhdCBib3RoZXJzIG1lLCBhbmQgdGhhdCBpcyB0aGF0CmZvciBsYXJnZSBy aW5ncyB3aGljaCBhcmUgbm90IHBoeXNpY2FsbHkgY29udGlndW91cwp3ZSBkb24ndCBpbXBsZW1l bnQgdGhlIG9wdGltaXphdGlvbi4KCkZvciBzdXJlLCB0aGF0IGNhbiB3YWl0LCBidXQgSSB0aGlu ayBldmVudHVhbGx5IHdlIHNob3VsZAp2bWFwIGxhcmdlIHJpbmdzLgoKLS0gCk1TVAoKX19fX19f X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KbGludXgtYXJtLWtlcm5l bCBtYWlsaW5nIGxpc3QKbGludXgtYXJtLWtlcm5lbEBsaXN0cy5pbmZyYWRlYWQub3JnCmh0dHA6 Ly9saXN0cy5pbmZyYWRlYWQub3JnL21haWxtYW4vbGlzdGluZm8vbGludXgtYXJtLWtlcm5lbAo=