Just to follow up: which version of kexec/makedumpfile are required to have the parallel dump feature? The thread you referenced adds documentation how to use that and I grepped the source of makedumpfile 1.5.8 and couldn't find any references to the num-threads option? So what version of the code do I need to test that ? On 09/17/2015 09:32 AM, Nikolay Borisov wrote: > Hi Qiao, > > Thanks for the reply. So far I haven't been using the the compression > feature of makedumpfile. But I want to ask if anything wouldn't > compression make the dump process slower since in addition to having to > write the dump to disk it also has to compress it which would put more > strain on the cpu. Also, which part of the dump process is the bottleneck: > > - Reading from /proc/vmcore - that has mmap support so should be fairly > fast? > - Discarding unnecessary pages as memory is being scanned? > - Writing/compressing content to disk? > > Regards, > Nikolay > > On 09/17/2015 06:27 AM, qiaonuohan wrote: >> On 09/16/2015 04:30 PM, Nikolay Borisov wrote: >>> Hello, >>> >>> I've been using makedumpfile as the crash collector with the -d31 >>> parameter. The machine this is being run on usually have 128-256GB of >>> ram and the resulting crash dumps are in the range of 14-20gb which is >>> very bug for the type of analysis I'm usually performing on crashed >>> machine. I was wondering whether there is a way to further reduce the >>> size and the time to take the dump (now it takes around 25 minutes to >>> collect such a dump). I've seen reports where people with TBs of ram >>> take that long, meaning for a machine with 256gb it should be even >>> faster. I've been running this configuration on kernels 3.12.28 and 4.1 >>> where mmap for the vmcore file is supported. >>> >>> Please advise >> >> Hi nikolay, >> >> Yes, this issue is what we are concerning a lot. >> About the current situation, try --split, it will save time. >> >> >> And lzo/snappy instead of zlib, these two compression format are faster >> but need more space to save. Or if you still want zlib (to save space), >> try multiple threads, check the following site, it will help you: >> >> https://lists.fedoraproject.org/pipermail/kexec/2015-September/002322.html >> >>
