|
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-devel] ctx suddenly rises in HVM Xen Guest
Hello, I have tested HVM XEN GUEST performance with LMbench and found a problem with the context switch time in guest. Following results are with CREDIT scheduler, but SEDF scheduler has similar results. The context switch time will rise suddenly when the PROCESS NUMBER (in context switch microbenchmark) arrives a 'threshold', just like a step-function. Normally the 'threshold' of PROCESS NUMBER varies in the range of 35-44 (in UP HVM XEN guest) and 52-62 (in SMP HVM XEN guest), which is relevant to UP/SMP and size of processes defined by LMbench. Before the 'threshold' context switch time keeps a relative stable value, after threshold it also keeps a relative stable value. The native Linux has no such problem. *************************************** Comparison of Test Results 'size' denotes size of processes ProcNum denotes number of processes *************************************** (1) 'size=0k' HVM XEN UP-GUEST 3.58(ProcNum=42) 65.36(ProcNum=43) /* 'threshold' 43 */ HVM XEN SMP-Guest 29.71(ProcNum=60) 116.86(ProcNum=61) /* 'threshold' 61 */ (2) 'size=32k' HVM XEN UP-GUEST 3.01(ProcNum=37) 101.81(ProcNum=38) /* 'threshold' 38 */ HVM XEN SMP-Guest 31.53(ProcNum=53) 158.46(ProcNum=54) /* 'threshold' 54 */ I profiling the TLB misses with following configuration to see whether it is relevant to TLB misses or not. 1. Count TLB misses in Dom0 when DomU running modified context switch microbenchmark 40 times (with only ProcNum=32, which can gurantee it has not arrived 'threshold') 2. Count TLB misses in Dom0 when DomU running modified context switch microbenchmark 40 times (with only ProcNum=64, which can gurantee it has not arrived 'threshold') 3. Count TLB misses in Dom0 when no ctx microbenchmark running in DomU So the only difference between the three configurations are ProcNum and Running/NotRunning ctx microbenchmark in DomU. But results show that there is no obvious difference between ProcNum=32 and ProcNum=64. **************************************** TLB misses Comparison **************************************** DTLB-misses (/second) 4387800 (ProcNum=32) /* before 'threshold' */ 4326450 (ProcNum=64) /* after 'threshold' */ 2935300 (no ctx running) ITLB-misses (/second) 230167 (ProcNum=32) /* before 'threshold' */ 235384 (ProcNum=64) /* after 'threshold' */ 85988 (no ctx running) **************************************** version **************************************** Xen:xen-3.0.3-8 Dom0: 2.6.19-1.2911.6.5.fc6xen DomU: 2.6.22.9-61.fc6 Tools: lmbench-3.0-a8 oprofile 0.9.2 **************************************** CPUINFO **************************************** processor : 0 vendor_id : GenuineIntel cpu family : 6 model : 15 model name : Intel(R) Core(TM)2 CPU T7400 @ 2.16GHz stepping : 6 cpu MHz : 2168.220 cache size : 4096 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm bogomips : 5422.48 processor : 1 vendor_id : GenuineIntel cpu family : 6 model : 15 model name : Intel(R) Core(TM)2 CPU T7400 @ 2.16GHz stepping : 6 cpu MHz : 2168.220 cache size : 4096 KB fdiv_bug : no hlt_bug : no f00f_bug : no coma_bug : no fpu : yes fpu_exception : yes cpuid level : 10 wp : yes flags : fpu tsc msr pae mce cx8 apic mtrr mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm pbe nx lm constant_tsc up pni monitor ds_cpl vmx est tm2 ssse3 cx16 xtpr lahf_lm bogomips : 5422.48 Can anyone explain this problem for me? Any comments/advices will be appreciated. Songtao _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
|
 |
Lists.xenproject.org is hosted with RackSpace, monitoring our |