From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 66543280910 for ; Fri, 10 Mar 2017 08:26:25 -0500 (EST) Received: by mail-qk0-f199.google.com with SMTP id v125so166706299qkh.5 for ; Fri, 10 Mar 2017 05:26:25 -0800 (PST) Received: from mx1.redhat.com (mx1.redhat.com. [209.132.183.28]) by mx.google.com with ESMTPS id e134si8038344qka.272.2017.03.10.05.26.23 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Fri, 10 Mar 2017 05:26:24 -0800 (PST) Subject: Re: [virtio-dev] Re: [PATCH v7 kernel 3/5] virtio-balloon: implementation of VIRTIO_BALLOON_F_CHUNK_TRANSFER References: <1488519630-89058-1-git-send-email-wei.w.wang@intel.com> <1488519630-89058-4-git-send-email-wei.w.wang@intel.com> <20170308054813-mutt-send-email-mst@kernel.org> <58C279B7.2060106@intel.com> From: David Hildenbrand Message-ID: <2572fe97-4d28-fb34-4513-924959bc5cb2@redhat.com> Date: Fri, 10 Mar 2017 14:26:18 +0100 MIME-Version: 1.0 In-Reply-To: <58C279B7.2060106@intel.com> Content-Type: text/plain; charset=windows-1252 Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Wei Wang , "Michael S. Tsirkin" Cc: "virtio-dev@lists.oasis-open.org" , "kvm@vger.kernel.org" , "qemu-devel@nongnu.org" , "linux-kernel@vger.kernel.org" , "virtualization@lists.linux-foundation.org" , "linux-mm@kvack.org" , Liang Li , Paolo Bonzini , Cornelia Huck , Amit Shah , "Hansen, Dave" , Andrea Arcangeli , Liang Li Am 10.03.2017 um 11:02 schrieb Wei Wang: > On 03/08/2017 12:01 PM, Michael S. Tsirkin wrote: >> On Fri, Mar 03, 2017 at 01:40:28PM +0800, Wei Wang wrote: >>> From: Liang Li >>> >>> The implementation of the current virtio-balloon is not very >>> efficient, because the pages are transferred to the host one by one. >>> Here is the breakdown of the time in percentage spent on each >>> step of the balloon inflating process (inflating 7GB of an 8GB >>> idle guest). >>> >>> 1) allocating pages (6.5%) >>> 2) sending PFNs to host (68.3%) >>> 3) address translation (6.1%) >>> 4) madvise (19%) >>> >>> It takes about 4126ms for the inflating process to complete. >>> The above profiling shows that the bottlenecks are stage 2) >>> and stage 4). >>> >>> This patch optimizes step 2) by transfering pages to the host in >>> chunks. A chunk consists of guest physically continuous pages, and >>> it is offered to the host via a base PFN (i.e. the start PFN of >>> those physically continuous pages) and the size (i.e. the total >>> number of the pages). A normal chunk is formated as below: >>> ----------------------------------------------- >>> | Base (52 bit) | Size (12 bit)| >>> ----------------------------------------------- >>> For large size chunks, an extended chunk format is used: >>> ----------------------------------------------- >>> | Base (64 bit) | >>> ----------------------------------------------- >>> ----------------------------------------------- >>> | Size (64 bit) | >>> ----------------------------------------------- >>> >>> By doing so, step 4) can also be optimized by doing address >>> translation and madvise() in chunks rather than page by page. >>> >>> This optimization requires the negotation of a new feature bit, >>> VIRTIO_BALLOON_F_CHUNK_TRANSFER. >>> >>> With this new feature, the above ballooning process takes ~590ms >>> resulting in an improvement of ~85%. >>> >>> TODO: optimize stage 1) by allocating/freeing a chunk of pages >>> instead of a single page each time. >>> >>> Signed-off-by: Liang Li >>> Signed-off-by: Wei Wang >>> Suggested-by: Michael S. Tsirkin >>> Cc: Michael S. Tsirkin >>> Cc: Paolo Bonzini >>> Cc: Cornelia Huck >>> Cc: Amit Shah >>> Cc: Dave Hansen >>> Cc: Andrea Arcangeli >>> Cc: David Hildenbrand >>> Cc: Liang Li >>> Cc: Wei Wang >> Does this pass sparse? I see some endian-ness issues here. > > "pass sparse"- what does that mean? > I didn't see any complaints from "make" on my machine. https://kernel.org/doc/html/latest/dev-tools/sparse.html Static code analysis. You have to run it explicitly. -- Thanks, David -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org