Messages in this thread | | | Date | Thu, 24 Aug 2023 14:26:25 +0800 | Subject | Re: [PATCH v2 0/4] Extend migrate_misplaced_page() to support batch migration | From | Baolin Wang <> |
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On 8/24/2023 12:51 PM, Huang, Ying wrote: > Baolin Wang <baolin.wang@linux.alibaba.com> writes: > >> On 8/22/2023 10:47 AM, Huang, Ying wrote: >>> Baolin Wang <baolin.wang@linux.alibaba.com> 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);
Yes, I overlooked this. Thanks for reminding.
> >>> 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@linux.alibaba.com/t/#mc45929849b5d0e29b5fdd9d50425f8e95b8f2563 >>>> [2] https://lore.kernel.org/all/20230213123444.155149-1-ying.huang@intel.com/T/#u >>>> [3] https://lore.kernel.org/all/f8d47176-03a8-99bf-a813-b5942830fd73@arm.com/ >>>> >>>> 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(-)
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