On 09/18/2015 08:45 PM, Nikolay Borisov wrote: > 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? As I recall, it is OK to go on the test. > > 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 >>>> >>>> >>>> >>> . >>> >> >> > . > -- Regards Qiao Nuohan
