Messages in this thread | | | Date | Sat, 20 Jan 2024 10:13:19 +0800 | Subject | Re: [PATCH v2] mm: memory: move mem_cgroup_charge() into alloc_anon_folio() | From | Kefeng Wang <> |
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On 2024/1/19 23:46, Michal Hocko wrote: > On Fri 19-01-24 20:59:22, Kefeng Wang wrote: >>>>> GFP_TRANSHUGE_LIGHT is more interesting though because those do not dive >>>>> into the direct reclaim at all. With the current code they will reclaim >>>>> charges to free up the space for the allocated THP page and that defeats >>>>> the light mode. I have a vague recollection of preparing a patch to >>>> >>>> We are interesting to GFP_TRANSHUGE_LIGHT and _GFP_NORETRY as mentioned >>>> above. >>> >>> if mTHP can be smaller than COSTLY_ORDER then you are correct and >>> NORETRY makes a difference. Please mention that in the changelog as >>> well. >>> >> >> For memory cgroup charge, _GFP_NORETRY checked to make us directly skip >> mem_cgroup_oom(), it has no concern with folio order or COSTLY_ORDER when >> check _GFP_NORETRY in try_charge_memcg(), so I think NORETRY should >> always make difference for all large order folio. > > we do not OOM on COSTLY_ORDER (see mem_cgroup_oom). So NORETRY really > makes a difference for small orders.
I see what you mean, but we may describe the different processes, if GFP_TRANSHUGE | __GFP_NORETRY returned from vma_thp_gfp_mask(), then we never involved with mem_cgroup_oom(), since mem_cgroup_oom() will be skipped in try_charge_memcg(), that is what I want to say, and in this case, no oom for order < COSTLY_ORDER or order > COSTLY_ORDER. But if GFP is GFP_TRANHUGE, then we may enter mem_cgroup_oom(), and maybe oom if order < COSTLY_ORDER.
So Yes, NORETRY really makes a difference for small orders.
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