From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53826) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eLpq7-00054d-4X for qemu-devel@nongnu.org; Mon, 04 Dec 2017 07:27:19 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eLpq3-0004cn-Qf for qemu-devel@nongnu.org; Mon, 04 Dec 2017 07:27:15 -0500 Received: from szxga04-in.huawei.com ([45.249.212.190]:2117 helo=huawei.com) by eggs.gnu.org with esmtps (TLS1.0:DHE_RSA_AES_256_CBC_SHA1:32) (Exim 4.71) (envelope-from ) id 1eLpq3-0004bH-FP for qemu-devel@nongnu.org; Mon, 04 Dec 2017 07:27:11 -0500 Message-ID: <5A253EF5.6040300@huawei.com> Date: Mon, 4 Dec 2017 20:26:29 +0800 From: Shannon Zhao MIME-Version: 1.0 References: <1511505030-3669-1-git-send-email-yang.zhong@intel.com> <5A1A5C6E.9060409@huawei.com> <20171201105622.GB26237@yangzhon-Virtual> <74cccd14-e485-90d4-82d9-03355c05faca@redhat.com> <20171204120322.GA32151@yangzhon-Virtual> In-Reply-To: <20171204120322.GA32151@yangzhon-Virtual> Content-Type: text/plain; charset="ISO-8859-1" Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH v3] rcu: reduce more than 7MB heap memory by malloc_trim() List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Yang Zhong , Paolo Bonzini , stefanha@redhat.com Cc: qemu-devel@nongnu.org, weidong.huang@huawei.com, arei.gonglei@huawei.com, liujunjie23@huawei.com, wangxinxin.wang@huawei.com, stone.xulei@huawei.com, zhang.zhanghailiang@huawei.com, berrange@redhat.com Hi Yang, On 2017/12/4 20:03, Yang Zhong wrote: > On Fri, Dec 01, 2017 at 01:52:49PM +0100, Paolo Bonzini wrote: >> > On 01/12/2017 11:56, Yang Zhong wrote: >>> > > This issue should be caused by much times of system call by malloc_trim(), >>> > > Shannon's test script include 60 scsi disks and 31 ioh3420 devices. We need >>> > > trade-off between VM perforamance and memory optimization. Whether below >>> > > method is suitable? >>> > > >>> > > int num=1; >>> > > ...... >>> > > >>> > > #if defined(CONFIG_MALLOC_TRIM) >>> > > if(!(num++%5)) >>> > > { >>> > > malloc_trim(4 * 1024 * 1024); >>> > > } >>> > > #endif >>> > > >>> > > Any comments are welcome! Thanks a lot! >> > >> > Indeed something like this will do, perhaps only trim once per second? >> > > Hello Paolo, > > Thanks for comments! > If we do trim once per second, maybe the frequency is a little high, what'e > more, we need maintain one timer to call this, this also cost cpu resource. > > I added the log and did the test here with my test qemu command, when VM bootup, > which did more than 600 times free operations and 9 times memory trim in rcu > thread. If i use our ClearContainer qemu command, the memory trim will down > to 6 times. As for Shannon's test command, the malloc trim number will abosultly > increse. > > In my above method, the trim is only executed in the multiple of 5, which will > reduce trim times and do not heavily impact VM bootup performance. > > I also want to use synchronize_rcu() and free() to replace call_rcu(), but this > method serialize to malloc() and free(), which will reduce VM performance. > > The ultimate aim is to reduce trim system call during the VM bootup and running. > It's appreciated that if you have better suggestions. Maybe we can provide a QMP command or something else for user to trim the heap manually like the kernel sysfs interface /proc/sys/vm/drop_caches which provides an interface for user to drop the caches. So let user to decide whether it needs to trim the heap. Thanks, -- Shannon