From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:53795) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XfKZT-0003iX-2A for qemu-devel@nongnu.org; Fri, 17 Oct 2014 23:20:52 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1XfKZO-0003qn-DG for qemu-devel@nongnu.org; Fri, 17 Oct 2014 23:20:46 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:9698) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1XfKZN-0003oj-Mx for qemu-devel@nongnu.org; Fri, 17 Oct 2014 23:20:42 -0400 Message-ID: <5441DC6D.2060602@huawei.com> Date: Sat, 18 Oct 2014 11:20:13 +0800 From: Linhaifeng MIME-Version: 1.0 References: <1413534437-13516-1-git-send-email-haifeng.lin@huawei.com> <20141017083358.GB5874@redhat.com> <5440D9F7.5070708@huawei.com> <20141017132626.GA6628@redhat.com> In-Reply-To: <20141017132626.GA6628@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [PATCH] fix the memory leak for share hugepage List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: "Daniel P. Berrange" Cc: mst@redhat.com, qemu-devel@nongnu.org, jerry.lilijun@huawei.com On 2014/10/17 21:26, Daniel P. Berrange wrote: > On Fri, Oct 17, 2014 at 04:57:27PM +0800, Linhaifeng wrote: >> >> >> On 2014/10/17 16:33, Daniel P. Berrange wrote: >>> On Fri, Oct 17, 2014 at 04:27:17PM +0800, haifeng.lin@huawei.com wrote: >>>> From: linhaifeng >>>> >>>> The VM start with share hugepage should close the hugefile fd >>>> when exit.Because the hugepage fd may be send to other process >>>> e.g vhost-user If qemu not close the fd the other process can >>>> not free the hugepage otherwise exit process,this is ugly,so >>>> qemu should close all shared fd when exit. >>>> >>>> Signed-off-by: linhaifeng >>> >>> Err, all file descriptors are closed automatically when a process >>> exits. So manually calling close(fd) before exit can't have any >>> functional effect on a resource leak. >>> >>> If QEMU has sent the FD to another process, that process has a >>> completely separate copy of the FD. Closing the FD in QEMU will >>> not close the FD in the other process. You need the other process >>> to exit for the copy to be closed. >>> >>> Regards, >>> Daniel >>> >> Hi,daniel >> >> QEMU send the fd by unix domain socket.unix domain socket just install the fd to >> other process and inc the f_count,if qemu not close the fd the f_count is not dec. >> Then the other process even close the fd the hugepage would not freed whise the other process exit. > > The kernel always closes all FDs when a process exits. So if this FD is > not being correctly closed then it is a kernel bug. There should never > be any reason for an application to do close(fd) before exiting. > > Regards, > Daniel > Hi,daniel I don't think this is kernel's bug.May be this a problem about usage. If you open a file you should close it too. This is <>about how to free resource of file. http://linux.die.net/man/2/close I'm trying to describe my problem. For example, there are 2 VMs run with hugepage and the hugepage only for QEMU to use. Before run VM the meminfo is : HugePages_Total: 4096 HugePages_Free: 4096 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Run the two VMs.QEMU deal with hugepage as follow steps: 1.open 2.unlink 3.mmap 4.use memory of hugepage.After this step the meminfo is : HugePages_Total: 4096 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB 5.shutdown VM with signal 15 without close(fd).After this step the meminfo is : HugePages_Total: 4096 HugePages_Free: 4096 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Yes,it works well,like you said the kernel recycle all resources. For another example,there are 2 VMs run with hugepage and share the hugepage with vapp(a vhost-user application). Before run VM the meminfo is : HugePages_Total: 4096 HugePages_Free: 4096 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Run the first VM.QEMU deal with hugepage as follow steps: 1.open 2.unlink 3.mmap 4.use memory of hugepage and send the fd to vapp with unix domain socket.After this step the meminfo is: HugePages_Total: 4096 HugePages_Free: 2048 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Run the second VM.After this step the meminfo is: HugePages_Total: 4096 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB Then I want to close the first VM and run another VM.After close the first VM and close the fd in vapp the meminfo is : HugePages_Total: 4096 HugePages_Free: 0 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB So failed to run the third VM because the first VM have not free the hugepage.After apply this patch the meminfo is: HugePages_Total: 4096 HugePages_Free: 2048 HugePages_Rsvd: 0 HugePages_Surp: 0 Hugepagesize: 2048 kB So i can run the third VM success. -- Regards, Haifeng