Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> writes: > On 8/22/2023 10:47 AM, Huang, Ying wrote: >> Baolin Wang <baolin.wang@xxxxxxxxxxxxxxxxx> writes: >> >>> Hi, >>> >>> Currently, on our ARM servers with NUMA enabled, we found the cross-die latency >>> is a little larger that will significantly impact the workload's performance. >>> So on ARM servers we will rely on the NUMA balancing to avoid the cross-die >>> accessing. And I posted a patchset[1] to support speculative numa fault to >>> improve the NUMA balancing's performance according to the principle of data >>> locality. Moreover, thanks to Huang Ying's patchset[2], which introduced batch >>> migration as a way to reduce the cost of TLB flush, and it will also benefit >>> the migration of multiple pages all at once during NUMA balancing. >>> >>> So we plan to continue to support batch migration in do_numa_page() to improve >>> the NUMA balancing's performance, but before adding complicated batch migration >>> algorithm for NUMA balancing, some cleanup and preparation work need to do firstly, >>> which are done in this patch set. In short, this patchset extends the >>> migrate_misplaced_page() interface to support batch migration, and no functional >>> changes intended. >>> >>> In addition, these cleanup can also benefit the compound page's NUMA balancing, >>> which was discussed in previous thread[3]. IIUC, for the compound page's NUMA >>> balancing, it is possible that partial pages were successfully migrated, so it is >>> necessary to return the number of pages that were successfully migrated from >>> migrate_misplaced_page(). >> But I don't find the return number is used except as bool now. > > As I said above, this is a preparation for batch migration and > compound page NUMA balancing in future. > > In addition, after looking into the THP' NUMA migration, I found this > change is necessary for THP migration. Since it is possible that > partial subpages were successfully migrated if the THP is split, so > below THP numa fault statistics is not always correct: > > if (page_nid != NUMA_NO_NODE) > task_numa_fault(last_cpupid, page_nid, HPAGE_PMD_NR, > flags); > > I will try to fix this in next version. IIUC, THP will not be split for NUMA balancing. Please check the nosplit logic in migrate_pages_batch(). bool nosplit = (reason == MR_NUMA_MISPLACED); -- Best Regards, Huang, Ying >> Per my understanding, I still don't find much value of the changes >> except as preparation for batch migration in NUMA balancing. So I still > > IMO, only patch 3 is just a preparation for batch migration, but other > patches are some cleanups for migrate_misplaced_page(). I can drop the > preparation patches in this series and revise the commit message. > >> think it's better to wait for the whole series. Where we can check why >> these changes are necessary for batch migration. And I think that you >> will provide some number to justify the batch migration, including pros >> and cons. >> -- >> Best Regards, >> Huang, Ying >> >>> This series is based on the latest mm-unstable(d226b59b30cc). >>> >>> [1] https://lore.kernel.org/lkml/cover.1639306956.git.baolin.wang@xxxxxxxxxxxxxxxxx/t/#mc45929849b5d0e29b5fdd9d50425f8e95b8f2563 >>> [2] https://lore.kernel.org/all/20230213123444.155149-1-ying.huang@xxxxxxxxx/T/#u >>> [3] https://lore.kernel.org/all/f8d47176-03a8-99bf-a813-b5942830fd73@xxxxxxx/ >>> >>> Changes from v1: >>> - Move page validation into a new function suggested by Huang Ying. >>> - Change numamigrate_isolate_page() to boolean type. >>> - Update some commit message. >>> >>> Baolin Wang (4): >>> mm: migrate: factor out migration validation into >>> numa_page_can_migrate() >>> mm: migrate: move the numamigrate_isolate_page() into do_numa_page() >>> mm: migrate: change migrate_misplaced_page() to support multiple pages >>> migration >>> mm: migrate: change to return the number of pages migrated >>> successfully >>> >>> include/linux/migrate.h | 15 +++++++--- >>> mm/huge_memory.c | 23 +++++++++++++-- >>> mm/internal.h | 1 + >>> mm/memory.c | 43 ++++++++++++++++++++++++++- >>> mm/migrate.c | 64 +++++++++-------------------------------- >>> 5 files changed, 88 insertions(+), 58 deletions(-)
