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Re: [Qemu-devel] vm performance degradation after kvm live migration or
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From: |
Michael S. Tsirkin |
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Subject: |
Re: [Qemu-devel] vm performance degradation after kvm live migration or save-restore with ETP enabled |
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Date: |
Thu, 11 Jul 2013 13:28:25 +0300 |
On Thu, Jul 11, 2013 at 09:36:47AM +0000, Zhanghaoyu (A) wrote:
> hi all,
>
> I met similar problem to these, while performing live migration or
> save-restore test on the kvm platform (qemu:1.4.0, host:suse11sp2,
> guest:suse11sp2), running tele-communication software suite in guest,
> https://lists.gnu.org/archive/html/qemu-devel/2013-05/msg00098.html
> http://comments.gmane.org/gmane.comp.emulators.kvm.devel/102506
> http://thread.gmane.org/gmane.comp.emulators.kvm.devel/100592
> https://bugzilla.kernel.org/show_bug.cgi?id=58771
>
> After live migration or virsh restore [savefile], one process's CPU
> utilization went up by about 30%, resulted in throughput degradation of this
> process.
> oprofile report on this process in guest,
> pre live migration:
> CPU: CPU with timer interrupt, speed 0 MHz (estimated)
> Profiling through timer interrupt
> samples % app name symbol name
> 248 12.3016 no-vmlinux (no symbols)
> 78 3.8690 libc.so.6 memset
> 68 3.3730 libc.so.6 memcpy
> 30 1.4881 cscf.scu SipMmBufMemAlloc
> 29 1.4385 libpthread.so.0 pthread_mutex_lock
> 26 1.2897 cscf.scu SipApiGetNextIe
> 25 1.2401 cscf.scu DBFI_DATA_Search
> 20 0.9921 libpthread.so.0 __pthread_mutex_unlock_usercnt
> 16 0.7937 cscf.scu DLM_FreeSlice
> 16 0.7937 cscf.scu receivemessage
> 15 0.7440 cscf.scu SipSmCopyString
> 14 0.6944 cscf.scu DLM_AllocSlice
>
> post live migration:
> CPU: CPU with timer interrupt, speed 0 MHz (estimated)
> Profiling through timer interrupt
> samples % app name symbol name
> 1586 42.2370 libc.so.6 memcpy
> 271 7.2170 no-vmlinux (no symbols)
> 83 2.2104 libc.so.6 memset
> 41 1.0919 libpthread.so.0 __pthread_mutex_unlock_usercnt
> 35 0.9321 cscf.scu SipMmBufMemAlloc
> 29 0.7723 cscf.scu DLM_AllocSlice
> 28 0.7457 libpthread.so.0 pthread_mutex_lock
> 23 0.6125 cscf.scu SipApiGetNextIe
> 17 0.4527 cscf.scu SipSmCopyString
> 16 0.4261 cscf.scu receivemessage
> 15 0.3995 cscf.scu SipcMsgStatHandle
> 14 0.3728 cscf.scu Urilex
> 12 0.3196 cscf.scu DBFI_DATA_Search
> 12 0.3196 cscf.scu SipDsmGetHdrBitValInner
> 12 0.3196 cscf.scu SipSmGetDataFromRefString
>
> So, memcpy costs much more cpu cycles after live migration. Then, I restart
> the process, this problem disappeared. save-restore has the similar problem.
>
> perf report on vcpu thread in host,
> pre live migration:
> Performance counter stats for thread id '21082':
>
> 0 page-faults
> 0 minor-faults
> 0 major-faults
> 31616 cs
> 506 migrations
> 0 alignment-faults
> 0 emulation-faults
> 5075957539 L1-dcache-loads
> [21.32%]
> 324685106 L1-dcache-load-misses # 6.40% of all L1-dcache hits
> [21.85%]
> 3681777120 L1-dcache-stores
> [21.65%]
> 65251823 L1-dcache-store-misses # 1.77%
> [22.78%]
> 0 L1-dcache-prefetches
> [22.84%]
> 0 L1-dcache-prefetch-misses
> [22.32%]
> 9321652613 L1-icache-loads
> [22.60%]
> 1353418869 L1-icache-load-misses # 14.52% of all L1-icache hits
> [21.92%]
> 169126969 LLC-loads
> [21.87%]
> 12583605 LLC-load-misses # 7.44% of all LL-cache hits
> [ 5.84%]
> 132853447 LLC-stores
> [ 6.61%]
> 10601171 LLC-store-misses #7.9%
> [ 5.01%]
> 25309497 LLC-prefetches #30%
> [ 4.96%]
> 7723198 LLC-prefetch-misses
> [ 6.04%]
> 4954075817 dTLB-loads
> [11.56%]
> 26753106 dTLB-load-misses # 0.54% of all dTLB cache
> hits [16.80%]
> 3553702874 dTLB-stores
> [22.37%]
> 4720313 dTLB-store-misses #0.13%
> [21.46%]
> <not counted> dTLB-prefetches
> <not counted> dTLB-prefetch-misses
>
> 60.000920666 seconds time elapsed
>
> post live migration:
> Performance counter stats for thread id '1579':
>
> 0 page-faults
> [100.00%]
> 0 minor-faults
> [100.00%]
> 0 major-faults
> [100.00%]
> 34979 cs
> [100.00%]
> 441 migrations
> [100.00%]
> 0 alignment-faults
> [100.00%]
> 0 emulation-faults
> 6903585501 L1-dcache-loads
> [22.06%]
> 525939560 L1-dcache-load-misses # 7.62% of all L1-dcache hits
> [21.97%]
> 5042552685 L1-dcache-stores
> [22.20%]
> 94493742 L1-dcache-store-misses #1.8%
> [22.06%]
> 0 L1-dcache-prefetches
> [22.39%]
> 0 L1-dcache-prefetch-misses
> [22.47%]
> 13022953030 L1-icache-loads
> [22.25%]
> 1957161101 L1-icache-load-misses # 15.03% of all L1-icache hits
> [22.47%]
> 348479792 LLC-loads
> [22.27%]
> 80662778 LLC-load-misses # 23.15% of all LL-cache hits
> [ 5.64%]
> 198745620 LLC-stores
> [ 5.63%]
> 14236497 LLC-store-misses # 7.1%
> [ 5.41%]
> 20757435 LLC-prefetches
> [ 5.42%]
> 5361819 LLC-prefetch-misses # 25%
> [ 5.69%]
> 7235715124 dTLB-loads
> [11.26%]
> 49895163 dTLB-load-misses # 0.69% of all dTLB cache
> hits [16.96%]
> 5168276218 dTLB-stores
> [22.44%]
> 6765983 dTLB-store-misses #0.13%
> [22.24%]
> <not counted> dTLB-prefetches
> <not counted> dTLB-prefetch-misses
>
> The "LLC-load-misses" went up by about 16%. Then, I restarted the process in
> guest, the perf data back to normal,
> Performance counter stats for thread id '1579':
>
> 0 page-faults
> [100.00%]
> 0 minor-faults
> [100.00%]
> 0 major-faults
> [100.00%]
> 30594 cs
> [100.00%]
> 327 migrations
> [100.00%]
> 0 alignment-faults
> [100.00%]
> 0 emulation-faults
> 7707091948 L1-dcache-loads
> [22.10%]
> 559829176 L1-dcache-load-misses # 7.26% of all L1-dcache hits
> [22.28%]
> 5976654983 L1-dcache-stores
> [23.22%]
> 160436114 L1-dcache-store-misses
> [22.80%]
> 0 L1-dcache-prefetches
> [22.51%]
> 0 L1-dcache-prefetch-misses
> [22.53%]
> 13798415672 L1-icache-loads
> [22.28%]
> 2017724676 L1-icache-load-misses # 14.62% of all L1-icache hits
> [22.49%]
> 254598008 LLC-loads
> [22.86%]
> 16035378 LLC-load-misses # 6.30% of all LL-cache hits
> [ 5.36%]
> 307019606 LLC-stores
> [ 5.60%]
> 13665033 LLC-store-misses
> [ 5.43%]
> 17715554 LLC-prefetches
> [ 5.57%]
> 4187006 LLC-prefetch-misses
> [ 5.44%]
> 7811502895 dTLB-loads
> [10.72%]
> 40547330 dTLB-load-misses # 0.52% of all dTLB cache
> hits [16.31%]
> 6144202516 dTLB-stores
> [21.58%]
> 6313363 dTLB-store-misses
> [21.91%]
> <not counted> dTLB-prefetches
> <not counted> dTLB-prefetch-misses
>
> 60.000812523 seconds time elapsed
>
> If EPT disabled, this problem gone.
>
> I suspect that kvm hypervisor has business with this problem.
> Based on above suspect, I want to find the two adjacent versions of kvm-kmod
> which triggers this problem or not (e.g. 2.6.39, 3.0-rc1),
> and analyze the differences between this two versions, or apply the patches
> between this two versions by bisection method, finally find the key patches.
>
> Any better ideas?
>
> Thanks,
> Zhang Haoyu
Does this happen even if you migrate between two qemu instances on the
same CPU?
--
MST