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=DKIM_INVALID,DKIM_SIGNED, HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS autolearn=unavailable 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 9E1D1C43381 for ; Tue, 12 Mar 2019 15:47:01 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 6C49A214AE for ; Tue, 12 Mar 2019 15:47:01 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=fail reason="signature verification failed" (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="Hta5ADB6" Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1726689AbfCLPqx (ORCPT ); Tue, 12 Mar 2019 11:46:53 -0400 Received: from bedivere.hansenpartnership.com ([66.63.167.143]:41006 "EHLO bedivere.hansenpartnership.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726272AbfCLPqx (ORCPT ); Tue, 12 Mar 2019 11:46:53 -0400 Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 6B8298EE1ED; Tue, 12 Mar 2019 08:46:52 -0700 (PDT) Received: from bedivere.hansenpartnership.com ([127.0.0.1]) by localhost (bedivere.hansenpartnership.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xRUipMi-5v4r; Tue, 12 Mar 2019 08:46:52 -0700 (PDT) Received: from [153.66.254.194] (unknown [50.35.68.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by bedivere.hansenpartnership.com (Postfix) with ESMTPSA id ACA718EE0F5; Tue, 12 Mar 2019 08:46:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=20151216; t=1552405612; bh=rtBt5DLADL8t5XJ0aWEYYr4qVgiTJN0Y03AmnFBmALQ=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Hta5ADB6diO123b+O9GGsaD3lTLmZxm0/SklZjxqjxFxREBbKMqH2pQq9KC9TpqUY FtBLt58elI9vQLiHqAfSyBBJn+aScF4ecBuiM54tPSDYp7m2jwOVqEwLyHHPM9lpUr kiGaEaRYtHEEndxKTdxFwSggNcuYAAt4p59ArUEw= Message-ID: <1552405610.3083.17.camel@HansenPartnership.com> Subject: Re: [RFC PATCH V2 0/5] vhost: accelerate metadata access through vmap() From: James Bottomley To: "Michael S. Tsirkin" , Jason Wang Cc: David Miller , hch@infradead.org, kvm@vger.kernel.org, virtualization@lists.linux-foundation.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, peterx@redhat.com, linux-mm@kvack.org, aarcange@redhat.com, linux-arm-kernel@lists.infradead.org, linux-parisc@vger.kernel.org Date: Tue, 12 Mar 2019 08:46:50 -0700 In-Reply-To: <20190312075033-mutt-send-email-mst@kernel.org> References: <20190308141220.GA21082@infradead.org> <56374231-7ba7-0227-8d6d-4d968d71b4d6@redhat.com> <20190311095405-mutt-send-email-mst@kernel.org> <20190311.111413.1140896328197448401.davem@davemloft.net> <6b6dcc4a-2f08-ba67-0423-35787f3b966c@redhat.com> <20190311235140-mutt-send-email-mst@kernel.org> <76c353ed-d6de-99a9-76f9-f258074c1462@redhat.com> <20190312075033-mutt-send-email-mst@kernel.org> Content-Type: text/plain; charset="UTF-8" X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 Content-Transfer-Encoding: 8bit Sender: linux-parisc-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-parisc@vger.kernel.org On Tue, 2019-03-12 at 07:54 -0400, Michael S. Tsirkin wrote: > On Tue, Mar 12, 2019 at 03:17:00PM +0800, Jason Wang wrote: > > > > On 2019/3/12 上午11:52, Michael S. Tsirkin wrote: > > > On Tue, Mar 12, 2019 at 10:59:09AM +0800, Jason Wang wrote: [...] > > At least for -stable, we need the flush? > > > > > > > Three atomic ops per bit is way to expensive. > > > > > > Yes. > > > > Thanks > > See James's reply - I stand corrected we do kunmap so no need to > flush. Well, I said that's what we do on Parisc. The cachetlb document definitely says if you alter the data between kmap and kunmap you are responsible for the flush. It's just that flush_dcache_page() is a no- op on x86 so they never remember to add it and since it will crash parisc if you get it wrong we finally gave up trying to make them. But that's the point: it is a no-op on your favourite architecture so it costs you nothing to add it. James 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=-1.0 required=3.0 tests=DKIMWL_WL_HIGH,DKIM_SIGNED, DKIM_VALID,HEADER_FROM_DIFFERENT_DOMAINS,MAILING_LIST_MULTI,SPF_PASS 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 8E499C43381 for ; Tue, 12 Mar 2019 15:47:03 +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 270DC214AE for ; Tue, 12 Mar 2019 15:47:03 +0000 (UTC) Authentication-Results: mail.kernel.org; dkim=pass (2048-bit key) header.d=lists.infradead.org header.i=@lists.infradead.org header.b="UJySPCrz"; dkim=fail reason="signature verification failed" (1024-bit key) header.d=hansenpartnership.com header.i=@hansenpartnership.com header.b="Hta5ADB6" DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 270DC214AE Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=HansenPartnership.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:Mime-Version:References:In-Reply-To: Date:To:From:Subject:Message-ID:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bk0f30M6SRYPBl8VBuzsWZdtZncfpV9LQZ7ywWM7LbE=; b=UJySPCrzi61IQo lVr4IXFjmh+XjSZYL9vgD4XguSFZ5iDCf91sg4BD8huKtOh4cjoCG5AtlcMT66e7dPsleqh7MpXh+ ipUNHnfQBWkKtD/Wyg7jYrVr0EyuFKJF/UfrjaDfpLXXQFp2Ro0NtAEt710oRrMqxYBZOp9xQrUMY wKQZ1ZOjj194siyN5Le4D8dyHjA40gjp4ygd6OtixqTW3H4i1ie5MuvgTytMoNn3zYFEz7HFgCsy6 c2Eop5vv7dSmP36ld2bOAhZGXYmy4SGQB70T9NlzxlQDAxIhGVAPpoiZUPCN+Sj9jZWURX1jbcCAm OfSJ3xi74kuwtgTFaDUQ==; Received: from localhost ([127.0.0.1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.90_1 #2 (Red Hat Linux)) id 1h3jcH-0007ce-1H; Tue, 12 Mar 2019 15:46:57 +0000 Received: from bedivere.hansenpartnership.com ([66.63.167.143]) by bombadil.infradead.org with esmtps (Exim 4.90_1 #2 (Red Hat Linux)) id 1h3jcE-0007cK-8s for linux-arm-kernel@lists.infradead.org; Tue, 12 Mar 2019 15:46:55 +0000 Received: from localhost (localhost [127.0.0.1]) by bedivere.hansenpartnership.com (Postfix) with ESMTP id 6B8298EE1ED; Tue, 12 Mar 2019 08:46:52 -0700 (PDT) Received: from bedivere.hansenpartnership.com ([127.0.0.1]) by localhost (bedivere.hansenpartnership.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id xRUipMi-5v4r; Tue, 12 Mar 2019 08:46:52 -0700 (PDT) Received: from [153.66.254.194] (unknown [50.35.68.20]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by bedivere.hansenpartnership.com (Postfix) with ESMTPSA id ACA718EE0F5; Tue, 12 Mar 2019 08:46:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=simple/simple; d=hansenpartnership.com; s=20151216; t=1552405612; bh=rtBt5DLADL8t5XJ0aWEYYr4qVgiTJN0Y03AmnFBmALQ=; h=Subject:From:To:Cc:Date:In-Reply-To:References:From; b=Hta5ADB6diO123b+O9GGsaD3lTLmZxm0/SklZjxqjxFxREBbKMqH2pQq9KC9TpqUY FtBLt58elI9vQLiHqAfSyBBJn+aScF4ecBuiM54tPSDYp7m2jwOVqEwLyHHPM9lpUr kiGaEaRYtHEEndxKTdxFwSggNcuYAAt4p59ArUEw= Message-ID: <1552405610.3083.17.camel@HansenPartnership.com> Subject: Re: [RFC PATCH V2 0/5] vhost: accelerate metadata access through vmap() From: James Bottomley To: "Michael S. Tsirkin" , Jason Wang Date: Tue, 12 Mar 2019 08:46:50 -0700 In-Reply-To: <20190312075033-mutt-send-email-mst@kernel.org> References: <20190308141220.GA21082@infradead.org> <56374231-7ba7-0227-8d6d-4d968d71b4d6@redhat.com> <20190311095405-mutt-send-email-mst@kernel.org> <20190311.111413.1140896328197448401.davem@davemloft.net> <6b6dcc4a-2f08-ba67-0423-35787f3b966c@redhat.com> <20190311235140-mutt-send-email-mst@kernel.org> <76c353ed-d6de-99a9-76f9-f258074c1462@redhat.com> <20190312075033-mutt-send-email-mst@kernel.org> X-Mailer: Evolution 3.26.6 Mime-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20190312_084654_318227_03951153 X-CRM114-Status: GOOD ( 11.07 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Cc: aarcange@redhat.com, linux-parisc@vger.kernel.org, kvm@vger.kernel.org, netdev@vger.kernel.org, linux-kernel@vger.kernel.org, peterx@redhat.com, virtualization@lists.linux-foundation.org, hch@infradead.org, linux-mm@kvack.org, David Miller , linux-arm-kernel@lists.infradead.org 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 T24gVHVlLCAyMDE5LTAzLTEyIGF0IDA3OjU0IC0wNDAwLCBNaWNoYWVsIFMuIFRzaXJraW4gd3Jv dGU6Cj4gT24gVHVlLCBNYXIgMTIsIDIwMTkgYXQgMDM6MTc6MDBQTSArMDgwMCwgSmFzb24gV2Fu ZyB3cm90ZToKPiA+IAo+ID4gT24gMjAxOS8zLzEyIOS4iuWNiDExOjUyLCBNaWNoYWVsIFMuIFRz aXJraW4gd3JvdGU6Cj4gPiA+IE9uIFR1ZSwgTWFyIDEyLCAyMDE5IGF0IDEwOjU5OjA5QU0gKzA4 MDAsIEphc29uIFdhbmcgd3JvdGU6ClsuLi5dCj4gPiBBdCBsZWFzdCBmb3IgLXN0YWJsZSwgd2Ug bmVlZCB0aGUgZmx1c2g/Cj4gPiAKPiA+IAo+ID4gPiBUaHJlZSBhdG9taWMgb3BzIHBlciBiaXQg aXMgd2F5IHRvIGV4cGVuc2l2ZS4KPiA+IAo+ID4gCj4gPiBZZXMuCj4gPiAKPiA+IFRoYW5rcwo+ IAo+IFNlZSBKYW1lcydzIHJlcGx5IC0gSSBzdGFuZCBjb3JyZWN0ZWQgd2UgZG8ga3VubWFwIHNv IG5vIG5lZWQgdG8KPiBmbHVzaC4KCldlbGwsIEkgc2FpZCB0aGF0J3Mgd2hhdCB3ZSBkbyBvbiBQ YXJpc2MuICBUaGUgY2FjaGV0bGIgZG9jdW1lbnQKZGVmaW5pdGVseSBzYXlzIGlmIHlvdSBhbHRl ciB0aGUgZGF0YSBiZXR3ZWVuIGttYXAgYW5kIGt1bm1hcCB5b3UgYXJlCnJlc3BvbnNpYmxlIGZv ciB0aGUgZmx1c2guICBJdCdzIGp1c3QgdGhhdCBmbHVzaF9kY2FjaGVfcGFnZSgpIGlzIGEgbm8t Cm9wIG9uIHg4NiBzbyB0aGV5IG5ldmVyIHJlbWVtYmVyIHRvIGFkZCBpdCBhbmQgc2luY2UgaXQg d2lsbCBjcmFzaApwYXJpc2MgaWYgeW91IGdldCBpdCB3cm9uZyB3ZSBmaW5hbGx5IGdhdmUgdXAg dHJ5aW5nIHRvIG1ha2UgdGhlbS4KCkJ1dCB0aGF0J3MgdGhlIHBvaW50OiBpdCBpcyBhIG5vLW9w IG9uIHlvdXIgZmF2b3VyaXRlIGFyY2hpdGVjdHVyZSBzbwppdCBjb3N0cyB5b3Ugbm90aGluZyB0 byBhZGQgaXQuCgpKYW1lcwoKCl9fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19f X19fX19fX19fCmxpbnV4LWFybS1rZXJuZWwgbWFpbGluZyBsaXN0CmxpbnV4LWFybS1rZXJuZWxA bGlzdHMuaW5mcmFkZWFkLm9yZwpodHRwOi8vbGlzdHMuaW5mcmFkZWFkLm9yZy9tYWlsbWFuL2xp c3RpbmZvL2xpbnV4LWFybS1rZXJuZWwK