From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:35815) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1eBx7V-0008B7-4v for qemu-devel@nongnu.org; Tue, 07 Nov 2017 01:12:22 -0500 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1eBx7R-0002zM-47 for qemu-devel@nongnu.org; Tue, 07 Nov 2017 01:12:21 -0500 Received: from mail-it0-x22b.google.com ([2607:f8b0:4001:c0b::22b]:50180) by eggs.gnu.org with esmtps (TLS1.0:RSA_AES_128_CBC_SHA1:16) (Exim 4.71) (envelope-from ) id 1eBx7Q-0002yi-Sa for qemu-devel@nongnu.org; Tue, 07 Nov 2017 01:12:17 -0500 Received: by mail-it0-x22b.google.com with SMTP id 72so1059887itl.5 for ; Mon, 06 Nov 2017 22:12:16 -0800 (PST) References: <80415da5-4eef-bf85-b617-fadc3dae4475@redhat.com> <20171106115931.GB3898@lemon> <78a404c5-fb2f-6fdf-c307-107ff1af4342@redhat.com> <5e0576f6-bb91-7e6e-7a1d-391d18717c0d@ozlabs.ru> From: Alexey Kardashevskiy Message-ID: Date: Tue, 7 Nov 2017 17:12:10 +1100 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8 Content-Language: en-AU Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] qemu core file size List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Wanpeng Li Cc: Paolo Bonzini , Fam Zheng , "qemu-devel@nongnu.org Developers" On 07/11/17 17:02, Wanpeng Li wrote: > Hi Alexey, > 2017-11-07 13:46 GMT+08:00 Alexey Kardashevskiy : >> On 07/11/17 01:08, Paolo Bonzini wrote: >>> On 06/11/2017 13:18, Wanpeng Li wrote: >>>> 2017-11-06 20:02 GMT+08:00 Paolo Bonzini : >>>>> On 06/11/2017 12:59, Fam Zheng wrote: >>>>>>>> Could you point out the patchset for the fix? >>>>>>> Between 447b0d0b9ee8a0ac216c3186e0f3c427a1001f0c and >>>>>>> 092aa2fc65b7a35121616aad8f39d47b8f921618. >>>>>> Not sure how these relate to the core size, but I've tested upstream >>>>>> (ec7a8bf0b8f7dc7288fe8745464ee8217528cc6c) and with dump-guest-core=off the core >>>>>> file is 363M, still significantly larger than rss (~73M). >>>>>> >>>>>> What is bloating the core file? >>>>> >>>>> My guess would have been fragmented heap. The core file, unlike the >>>>> RSS, includes all the mmaped memory (e.g. from shared libraries) that >>>>> has never been used. >>>>> >>>>> For example, all the Ceph/Gluster/PulseAudio/SPICE/whatever libraries >>>>> are included in the core file but likely are not in the RSS. >>>> >>>> Do you mean not use Memory API will avoid the fragmented heap? >>> >>> The high memory usage from the memory API causes excessive >>> fragmentation. Alexey's work should help reducing memory usage and thus >>> the fragmentation. >> >> Since centos6 does not have this issue and centos7 does, I'd suggest >> MALLOC_ARENA_MAX&co >> https://www.gnu.org/software/libc/manual/html_node/Memory-Allocation-Tunables.html > > Thanks for the inputs. What's the recommend glibc.malloc.arena_max > value from you? :) I have no idea, you have to try different values as you are the one who is unhappy about the sizes :) I do not normally mess with this as things should just work with the defaults whatever they are. > >> >> glibc changed some defaults between rhel/centos 6 and 7 if I recall >> correctly, and these arenas now create big anon mappings per thread, these >> are not really touched (so they do not use resident memory) but may appear >> in these dumps, dunno. >> >> btw do you configure the machine to make "kill -11" produce qemu core dumps? > > Yeah, some tuning in /etc/libvirt/qemu.conf, max_core="unlimited", > dump_guest_core=0 dump_guest_core=0 should mean "no dumps", no? Do you know how to enable this without libvirt? -- Alexey