[PATCH v4] Improve the performance of --num-threads -d 31

[Minfei Huang]

On 03/15/16 at 03:12pm, "Zhou, Wenjian/周文剑" wrote:
> Hello Minfei,
> 
> I guess the result is affected by the caches.
> How about executing the following command before running makedumpfile each time?
> # echo 3 > /proc/sys/vm/drop_caches

All of cache will be dropped before starting new test. Hmm, it is
limited to debug in kdump kernel. I will use "strace" to debug it later.

Thanks
Minfei

> 
> -- 
> Thanks
> Zhou
> 
> On 03/15/2016 02:34 PM, Minfei Huang wrote:
> >Hi, Zhou.
> >
> >I have applied this patch base on 1.5.9. There are several testcases I
> >have tested.
> >
> >- makedumpfile --num-threads 64 -d 31
> >     real    0m0.010s
> >     user    0m0.002s
> >     sys 0m0.009s
> >
> >- makedumpfile --num-threads 31 -d 31
> >     real    2m40.915s
> >     user    10m50.900s
> >     sys 23m9.664s
> >
> >makedumpfile --num-threads 30 -d 31
> >     real    0m0.006s
> >     user    0m0.002s
> >     sys 0m0.004s
> >
> >makedumpfile --num-threads 32 -d 31
> >     real    0m0.007s
> >     user    0m0.002s
> >     sys 0m0.005s
> >
> >- makedumpfile --num-threads 8 -d 31
> >     real    2m32.692s
> >     user    7m4.630s
> >     sys 2m0.369s
> >
> >- makedumpfile --num-threads 1 -d 31
> >     real    4m42.423s
> >     user    7m27.153s
> >     sys 0m22.490s
> >
> >- makedumpfile.orig -d 31
> >     real    4m1.297s
> >     user    3m39.696s
> >     sys 0m15.200s
> >
> >This patch has a huge increment to the filter performance under 31. But
> >it is not stable, since makedumpfile fails to dump vmcore intermittently.
> >You can find the above test result, makedumpfile fails to dump vmcore
> >with option --num-threads 64, also it may occur with option
> >--number-threads 8.
> >
> >Thanks
> >Minfei