Re: [Qemu-devel] qemu core file size

[Wanpeng Li]

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