On 07/11/17 17:16, Wanpeng Li wrote: > 2017-11-07 14:12 GMT+08:00 Alexey Kardashevskiy <a...@ozlabs.ru>: >> On 07/11/17 17:02, Wanpeng Li wrote: >>> Hi Alexey, >>> 2017-11-07 13:46 GMT+08:00 Alexey Kardashevskiy <a...@ozlabs.ru>: >>>> 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 <pbonz...@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. >>>> >>>> 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.
So I tried: - QEMU with "-smp 8" and "(gdb) generate-core-file 1" creates 820MB file; - QEMU with "-smp 256" creates 11GB file, - QEMU with "-smp 256" with MALLOC_ARENA_MAX=1 creates 2.5GB file, - QEMU with "-smp 128" with MALLOC_ARENA_MAX=1 creates 1.3GB file; - QEMU with "-smp 1" creates 290MB file; - QEMU with "-smp 1" with MALLOC_ARENA_MAX=1 creates 222MB file. It is "qemu-system-ppc64 -nodefaults -m 2G -enable-kvm -S" (i.e. stopped) pretty much. -- Alexey
