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#include >>>> +#include >>>> >>>> #include >>>> >>>> @@ -51,12 +52,6 @@ >>>> #include "internal.h" >>>> #include "swap.h" >>>> >>>> -/* For now, never offload. Wired up in later patch. */ >>>> -static bool migrate_should_offload(int reason) >>>> -{ >>>> - return false; >>>> -} >>>> - >>>> static const struct movable_operations *offline_movable_ops; >>>> static const struct movable_operations *zsmalloc_movable_ops; >>>> >>>> @@ -2050,7 +2045,7 @@ static int migrate_pages_batch(struct list_head *from, >>>> >>>> /* Batch-copy eligible folios before the move phase */ >>>> if (!list_empty(&unmap_batch)) >>>> - migrate_folios_mc_copy(&dst_batch, &unmap_batch, nr_batch); >>>> + migrate_offload_batch_copy(&dst_batch, &unmap_batch, nr_batch); >>>> >>>> retry = 1; >>>> for (pass = 0; pass < nr_pass && retry; pass++) { >>> >>> Found a difference between v5 and v6 here. In v5, migrate_pages_batch() >>> checks the return value of migrate_offload_batch_copy() and acts >>> accordingly. While in v6, it does not. Why was this changed? >>> >>> IIUC, FOLIO_CONTENT_COPIED is now used to indicate a copy failure. Is >>> this necessary? Is it possible that some (but not all) folios fail to >>> be copied? >> >> Based on the discussion[1], FOLIO_CONTENT_COPIED is used to indicate both >> 1. folio is copied via offloading, and 2. MC copy failure. So the code >> no longer needs to store the return value of migrate_offload_batch_copy() >> and can just check dst->migrate_info & FOLIO_CONTENT_COPIED. >> >> For 32bit, FOLIO_CONTENT_COPIED is always 0, so all folios are always >> copied in the serialized path. Hmm, that might be causing double copying, >> since migrate_folios_mc_copy() copies batched folios and later >> migrate_folios_move() copies them again since >> dst->migrate_info & FOLIO_CONTENT_COPIED is always false. Maybe we could >> make migrate_folios_mc_copy() return immediately in 32bit, otherwise, >> we will need to find somewhere else to store FOLIO_CONTENT_COPIED. >> >> [1] https://lore.kernel.org/all/c2bfdf39-8caa-43bd-b1ad-2285b4cc767a@amd.com/ >> >>> > It is not cause double copying. > migrate_should_offload() /and migrate_offload_enabled > gate if folio can be added to unmap_batch/dst_batch. So migrate_should_offload() is actually migrate_should_offload_batched_copy(). 32BIT does not get batched copy nor offloaded copy. > > migrate_offload_enabled branch is enabled from the offload driver like DCBM (which > again depends on 64_BIT) will call migrate_offload_register(). > > I think I can add a defensive 64_BIT check in migrate_should_offload() to prevent > any potential bugs. I think a better name would be helpful and sufficient. BTW, ideally, batched copy and offloaded copy are two separate features and could be enabled separately. But considering the hassle of finding a place to store FOLIO_CONTENT_COPIED on 32BIT, it might be fine to have a combined batched and offloaded copy. Best Regards, Yan, Zi