----- Original Message ----- > From: "Wenjian Zhou/???" <zhouwj-fnst at cn.fujitsu.com> > To: "Chao Fan" <cfan at redhat.com> > Cc: "Atsushi Kumagai" <ats-kumagai at wm.jp.nec.com>, kexec at lists.infradead.org > Sent: Thursday, December 10, 2015 6:32:32 PM > Subject: Re: [PATCH RFC 00/11] makedumpfile: parallel processing > > On 12/10/2015 05:58 PM, Chao Fan wrote: > > > > > > ----- Original Message ----- > >> From: "Wenjian Zhou/???" <zhouwj-fnst at cn.fujitsu.com> > >> To: "Atsushi Kumagai" <ats-kumagai at wm.jp.nec.com> > >> Cc: kexec at lists.infradead.org > >> Sent: Thursday, December 10, 2015 5:36:47 PM > >> Subject: Re: [PATCH RFC 00/11] makedumpfile: parallel processing > >> > >> On 12/10/2015 04:14 PM, Atsushi Kumagai wrote: > >>>> Hello Kumagai, > >>>> > >>>> On 12/04/2015 10:30 AM, Atsushi Kumagai wrote: > >>>>> Hello, Zhou > >>>>> > >>>>>> On 12/02/2015 03:24 PM, Dave Young wrote: > >>>>>>> Hi, > >>>>>>> > >>>>>>> On 12/02/15 at 01:29pm, "Zhou, Wenjian/???" wrote: > >>>>>>>> I think there is no problem if other test results are as expected. > >>>>>>>> > >>>>>>>> --num-threads mainly reduces the time of compressing. > >>>>>>>> So for lzo, it can't do much help at most of time. > >>>>>>> > >>>>>>> Seems the help of --num-threads does not say it exactly: > >>>>>>> > >>>>>>> [--num-threads THREADNUM]: > >>>>>>> Using multiple threads to read and compress data of each > >>>>>>> page > >>>>>>> in parallel. > >>>>>>> And it will reduces time for saving DUMPFILE. > >>>>>>> This feature only supports creating DUMPFILE in > >>>>>>> kdump-comressed format from > >>>>>>> VMCORE in kdump-compressed format or elf format. > >>>>>>> > >>>>>>> Lzo is also a compress method, it should be mentioned that > >>>>>>> --num-threads only > >>>>>>> supports zlib compressed vmcore. > >>>>>>> > >>>>>> > >>>>>> Sorry, it seems that something I said is not so clear. > >>>>>> lzo is also supported. Since lzo compresses data at a high speed, the > >>>>>> improving of the performance is not so obvious at most of time. > >>>>>> > >>>>>>> Also worth to mention about the recommended -d value for this > >>>>>>> feature. > >>>>>>> > >>>>>> > >>>>>> Yes, I think it's worth. I forgot it. > >>>>> > >>>>> I saw your patch, but I think I should confirm what is the problem > >>>>> first. > >>>>> > >>>>>> However, when "-d 31" is specified, it will be worse. > >>>>>> Less than 50 buffers are used to cache the compressed page. > >>>>>> And even the page has been filtered, it will also take a buffer. > >>>>>> So if "-d 31" is specified, the filtered page will use a lot > >>>>>> of buffers. Then the page which needs to be compressed can't > >>>>>> be compressed parallel. > >>>>> > >>>>> Could you explain why compression will not be parallel in more detail ? > >>>>> Actually the buffers are used also for filtered pages, it sounds > >>>>> inefficient. > >>>>> However, I don't understand why it prevents parallel compression. > >>>>> > >>>> > >>>> Think about this, in a huge memory, most of the page will be filtered, > >>>> and > >>>> we have 5 buffers. > >>>> > >>>> page1 page2 page3 page4 page5 page6 page7 > >>>> ..... > >>>> [buffer1] [2] [3] [4] [5] > >>>> unfiltered filtered filtered filtered filtered unfiltered > >>>> filtered > >>>> > >>>> Since filtered page will take a buffer, when compressing page1, > >>>> page6 can't be compressed at the same time. > >>>> That why it will prevent parallel compression. > >>> > >>> Thanks for your explanation, I understand. > >>> This is just an issue of the current implementation, there is no > >>> reason to stand this restriction. > >>> > >>>>> Further, according to Chao's benchmark, there is a big performance > >>>>> degradation even if the number of thread is 1. (58s vs 240s) > >>>>> The current implementation seems to have some problems, we should > >>>>> solve them. > >>>>> > >>>> > >>>> If "-d 31" is specified, on the one hand we can't save time by > >>>> compressing > >>>> parallel, on the other hand we will introduce some extra work by adding > >>>> "--num-threads". So it is obvious that it will have a performance > >>>> degradation. > >>> > >>> Sure, there must be some overhead due to "some extra work"(e.g. exclusive > >>> lock), > >>> but "--num-threads=1 is 4 times slower than --num-threads=0" still sounds > >>> too slow, the degradation is too big to be called "some extra work". > >>> > >>> Both --num-threads=0 and --num-threads=1 are serial processing, > >>> the above "buffer fairness issue" will not be related to this > >>> degradation. > >>> What do you think what make this degradation ? > >>> > >> > >> I can't get such result at this moment, so I can't do some further > >> investigation > >> right now. I guess it may be caused by the underlying implementation of > >> pthread. > >> I reviewed the test result of the patch v2 and found in different > >> machines, > >> the results are quite different. > > > > Hi Zhou Wenjian, > > > > I have done more tests in another machine with 128G memory, and get the > > result: > > > > the size of vmcore is 300M in "-d 31" > > makedumpfile -l --message-level 1 -d 31: > > time: 8.6s page-faults: 2272 > > > > makedumpfile -l --num-threads 1 --message-level 1 -d 31: > > time: 28.1s page-faults: 2359 > > > > > > and the size of vmcore is 2.6G in "-d 0". > > In this machine, I get the same result as yours: > > > > > > makedumpfile -c --message-level 1 -d 0: > > time: 597s page-faults: 2287 > > > > makedumpfile -c --num-threads 1 --message-level 1 -d 0: > > time: 602s page-faults: 2361 > > > > makedumpfile -c --num-threads 2 --message-level 1 -d 0: > > time: 337s page-faults: 2397 > > > > makedumpfile -c --num-threads 4 --message-level 1 -d 0: > > time: 175s page-faults: 2461 > > > > makedumpfile -c --num-threads 8 --message-level 1 -d 0: > > time: 103s page-faults: 2611 > > > > > > But the machine of my first test is not under my control, should I wait for > > the first machine to do more tests? > > If there are still some problems in my tests, please tell me. > > > > Thanks a lot for your test, it seems that there is nothing wrong. > And I haven't got any idea about more tests... > > Could you provide the information of your cpu ? > I will do some further investigation later. > OK, of course, here is the information of cpu: # lscpu Architecture: x86_64 CPU op-mode(s): 32-bit, 64-bit Byte Order: Little Endian CPU(s): 48 On-line CPU(s) list: 0-47 Thread(s) per core: 1 Core(s) per socket: 6 Socket(s): 8 NUMA node(s): 8 Vendor ID: AuthenticAMD CPU family: 16 Model: 8 Model name: Six-Core AMD Opteron(tm) Processor 8439 SE Stepping: 0 CPU MHz: 2793.040 BogoMIPS: 5586.22 Virtualization: AMD-V L1d cache: 64K L1i cache: 64K L2 cache: 512K L3 cache: 5118K NUMA node0 CPU(s): 0,8,16,24,32,40 NUMA node1 CPU(s): 1,9,17,25,33,41 NUMA node2 CPU(s): 2,10,18,26,34,42 NUMA node3 CPU(s): 3,11,19,27,35,43 NUMA node4 CPU(s): 4,12,20,28,36,44 NUMA node5 CPU(s): 5,13,21,29,37,45 NUMA node6 CPU(s): 6,14,22,30,38,46 NUMA node7 CPU(s): 7,15,23,31,39,47 Flags: fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush mmx fxsr sse sse2 ht syscall mmxext fxsr_opt pdpe1gb rdtscp lm 3dnowext 3dnow constant_tsc rep_good nopl nonstop_tsc extd_apicid pni monitor cx16 popcnt lahf_lm cmp_legacy svm extapic cr8_legacy abm sse4a misalignsse 3dnowprefetch osvw ibs skinit wdt hw_pstate npt lbrv svm_lock nrip_save pausefilter vmmcall > But I still believe it's better not to use "-l -d 31" and "--num-threads" > at the same time, though it's very strange that the performance > degradation is so big. > > -- > Thanks > Zhou > > > Thanks, > > Chao Fan > > > > > >> > >> It seems that I can get almost the same result of Chao from "PRIMEQUEST > >> 1800E". > >> > >> ################################### > >> - System: PRIMERGY RX300 S6 > >> - CPU: Intel(R) Xeon(R) CPU x5660 > >> - memory: 16GB > >> ################################### > >> ************ makedumpfile -d 7 ****************** > >> core-data 0 256 > >> threads-num > >> -l > >> 0 10 144 > >> 4 5 110 > >> 8 5 111 > >> 12 6 111 > >> > >> ************ makedumpfile -d 31 ****************** > >> core-data 0 256 > >> threads-num > >> -l > >> 0 0 0 > >> 4 2 2 > >> 8 2 3 > >> 12 2 3 > >> > >> ################################### > >> - System: PRIMEQUEST 1800E > >> - CPU: Intel(R) Xeon(R) CPU E7540 > >> - memory: 32GB > >> ################################### > >> ************ makedumpfile -d 7 ****************** > >> core-data 0 256 > >> threads-num > >> -l > >> 0 34 270 > >> 4 63 154 > >> 8 64 131 > >> 12 65 159 > >> > >> ************ makedumpfile -d 31 ****************** > >> core-data 0 256 > >> threads-num > >> -l > >> 0 2 1 > >> 4 48 48 > >> 8 48 49 > >> 12 49 50 > >> > >>>> I'm not so sure if it is a problem that the performance degradation is > >>>> so > >>>> big. > >>>> But I think if in other cases, it works as expected, this won't be a > >>>> problem( > >>>> or a problem needs to be fixed), for the performance degradation > >>>> existing > >>>> in theory. > >>>> > >>>> Or the current implementation should be replaced by a new arithmetic. > >>>> For example: > >>>> We can add an array to record whether the page is filtered or not. > >>>> And only the unfiltered page will take the buffer. > >>> > >>> We should discuss how to implement new mechanism, I'll mention this > >>> later. > >>> > >>>> But I'm not sure if it is worth. > >>>> For "-l -d 31" is fast enough, the new arithmetic also can't do much > >>>> help. > >>> > >>> Basically the faster, the better. There is no obvious target time. > >>> If there is room for improvement, we should do it. > >>> > >> > >> Maybe we can improve the performance of "-c -d 31" in some case. > >> > >> BTW, we can easily get the theoretical performance by using the "--split". > >> > >> -- > >> Thanks > >> Zhou > >> > >> > >> > >> _______________________________________________ > >> kexec mailing list > >> kexec at lists.infradead.org > >> http://lists.infradead.org/mailman/listinfo/kexec > >> > > > > > _______________________________________________ > kexec mailing list > kexec at lists.infradead.org > http://lists.infradead.org/mailman/listinfo/kexec >
