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From: Wanpeng Li <kernellwp@gmail.com>
Date: Tue, 7 Nov 2017 09:22:09 +0800
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Subject: Re: [Qemu-devel] qemu core file size
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To: Paolo Bonzini <pbonzini@redhat.com>
Cc: Fam Zheng <famz@redhat.com>, Alexey Kardashevskiy <aik@ozlabs.ru>, "qemu-devel@nongnu.org Developers" <qemu-devel@nongnu.org>

2017-11-06 22:08 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
> On 06/11/2017 13:18, Wanpeng Li wrote:
>> 2017-11-06 20:02 GMT+08:00 Paolo Bonzini <pbonzini@redhat.com>:
>>> 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.

But as Fam mentioned, the latest qemu still has issue.

Regards,
Wanpeng Li