On 02/17/2017 04:54 PM, Anshuman Khandual wrote: > This patch series is base on the work posted by Zi Yan back in > November 2016 (https://lkml.org/lkml/2016/11/22/457) but includes some > amount clean up and re-organization. This series depends on THP migration > optimization patch series posted by Naoya Horiguchi on 8th November 2016 > (https://lwn.net/Articles/705879/). Though Zi Yan has recently reposted > V3 of the THP migration patch series (https://lwn.net/Articles/713667/), > this series is yet to be rebased. > > Primary motivation behind this patch series is to achieve higher > bandwidth of memory migration when ever possible using multi threaded > instead of a single threaded copy. Did all the experiments using a two > socket X86 sytsem (Intel(R) Xeon(R) CPU E5-2650). All the experiments > here have same allocation size 4K * 100000 (which did not split evenly > for the 2MB huge pages). Here are the results. > > Vanilla: > > Moved 100000 normal pages in 247.000000 msecs 1.544412 GBs > Moved 100000 normal pages in 238.000000 msecs 1.602814 GBs > Moved 195 huge pages in 252.000000 msecs 1.513769 GBs > Moved 195 huge pages in 257.000000 msecs 1.484318 GBs > > THP migration improvements: > > Moved 100000 normal pages in 302.000000 msecs 1.263145 GBs > Moved 100000 normal pages in 262.000000 msecs 1.455991 GBs > Moved 195 huge pages in 120.000000 msecs 3.178914 GBs > Moved 195 huge pages in 129.000000 msecs 2.957130 GBs > > THP migration improvements + Multi threaded page copy: > > Moved 100000 normal pages in 1589.000000 msecs 0.240069 GBs ** > Moved 100000 normal pages in 1932.000000 msecs 0.197448 GBs ** > Moved 195 huge pages in 54.000000 msecs 7.064254 GBs *** > Moved 195 huge pages in 86.000000 msecs 4.435694 GBs *** > > > ** Using multi threaded copy can be detrimental to performance if > used for regular pages which are way too small. But then the > framework provides the means to use it if some kernel/driver > caller or user application wants to use it. > > *** These applications have used the new MPOL_MF_MOVE_MT flag while > calling the system calls like mbind() and move_pages(). > > On POWER8 the improvements are similar when tested with a draft patch > which enables migration at PMD level. Not putting out the results here > as the kernel is not stable with the that draft patch and crashes some > times. We are working on enabling PMD level migration on POWER8 and will > test this series out thoroughly when its ready. > > Patch Series Description:: > > Patch 1: Add new parameter to migrate_page_copy and copy_huge_page so > that it can differentiate between when to use single threaded > version (MIGRATE_ST) or multi threaded version (MIGRATE_MT). > > Patch 2: Make migrate_mode types non-exclusive. > > Patch 3: Add copy_pages_mthread function which does the actual multi > threaded copy. This involves splitting the copy work into > chunks, selecting threads and submitting copy jobs in the > work queues. > > Patch 4: Add new migrate mode MIGRATE_MT to be used by higher level > migration functions. > > Patch 5: Add new migration flag MPOL_MF_MOVE_MT for migration system > calls to be used in the user space. > > Patch 6: Define global mt_page_copy tunable which turns on the multi > threaded page copy no matter what for all migrations on the > system. > > Outstanding Issues:: > > Issue 1: The usefulness of the global multi threaded copy tunable i.e > vm.mt_page_copy. It makes sense and helps in validating the > framework. Should this be moved to debugfs instead ? > > Issue 2: We choose nr_copythreads = 8 as maximum number of threads on > a node can be 8 on any architecture (Which is on POWER8 if > I am not missing any other arch which might have equal or > more number of threads per node). It just denotes max number > of threads and we will be adjusted based on cpumask_weight > value on destination node. Can we do better, suggestions ? > > Issue 3: Multi threaded page migration works best with threads allocated > at different physical cores, not all in the same hyper-threaded > core. Work queues submitted jobs consume scheduler slots from > the given thread to execute the copy. This can interfere with > scheduling and affect some already running tasks on the system. > Should we be looking into arch topology information, scheduler > cpu idle details to decide on which threads to use before going > for multi threaded copy ? Abort multi threaded copy and fallback > to regular copy at times when the parameters are not good ? > > Any comments, suggestions are welcome. Hello Vlastimil/Michal/Minchan/Mel/Dave, Apart from the comments from Naoya on a different thread posted by Zi Yan, I did not get any more review comments on this series. Could you please kindly have a look on the over all design and its benefits from page migration performance point of view and let me know your views. Thank you. + Naoya Horiguchi <n-horiguchi@xxxxxxxxxxxxx> Regards Anshuman -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
