Yeah, I did see the commit browser. But in my case I haven't even tested the split option so I guess there are things to try. Am I correct in my understanding as to how --split is supposed to work ( i tried that to no avail though): My core_collector line is this: core_collector makedumpfile --message-level 1 -d 3 --split dump1 dump2 dump3 dump4 dump5 dump6 And then in /etc/sysconfig/kdump I have: KDUMP_COMMANDLINE_APPEND="irqpoll nr_cpus=6 reset_devices cgroup_disable=memory mce=off" (the machine I'm testing on has 4 cores x2 hyperthreads so 8 logical cores in total). Do I need to do something else to utilize the --split option? On 09/18/2015 05:38 AM, qiaonuohan wrote: > On 09/17/2015 02:32 PM, 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? > > I cannot recall percentage of each part. But writing/compression takes most > of the time > > 1. mmap is used for reading faster > 2. --split is used to split the dump task into several processes, so > compressing > and writing will be speeded up. > 3. multiple-thread is another option for speeding up compressing, it is > a recently > committed patch, so you cannot find it in the master branch, checkout > devel branch > or find it here: > > http://sourceforge.net/p/makedumpfile/code/commit_browser > > Make makedumpfile available to read and compress pages parallelly. > >> >> 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 >>> >>> >>> >> . >> > >
