On 06/26/2015 03:07 PM, Atsushi Kumagai wrote: > Hello Zhou, > >> >Hello Atsushi Kumagai, >> > >> >I test this patch set in several machines and the following is the benchmark. > Thanks for your report, it looks good as before. > I also did simple test on kernel 3.19 on a 5GB Virtual Machine, > but I can't get such good result as below: > > / # time makedumpfile -c --num-threads 0 /proc/vmcore /mnt/dumpfile > Copying data : [100.0 %] / > > The dumpfile is saved to /mnt/dumpfile. > > makedumpfile Completed. > real 0m 44.40s > user 0m 43.62s > sys 0m 0.69s > / # > > / # time makedumpfile -c --num-threads 4 /proc/vmcore /mnt/dumpfile > Copying data : [100.0 %] - > Copying data : [100.0 %] / > > The dumpfile is saved to /mnt/dumpfile. > > makedumpfile Completed. > real 5m 29.54s > user 6m 8.18s > sys 16m 33.25s > / # > > > There is a big performance degradation. > Do you have any ideas why this happens ? Does your Virtual Machine have more than 2 processors? If so, check the value:nr_cpus in KDUMP_COMMANDLINE_APPEND of /etc/sysconfig/kdump. It should be also set to the number larger than 2. To "--num-threads 4", the most suitable number of processors is 5. -- Thanks Zhou Wenjian
