Messages in this thread | | | Date | Tue, 6 Feb 2024 09:01:29 +0800 | Subject | Re: [PATCH v2] mm: hugetlb: improve the handling of hugetlb allocation failure for freed or in-use hugetlb | From | Baolin Wang <> |
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On 2/5/2024 10:47 PM, Michal Hocko wrote: > On Mon 05-02-24 20:50:51, Baolin Wang wrote: >> When handling the freed hugetlb or in-use hugetlb, we should ignore the >> failure of alloc_buddy_hugetlb_folio() to dissolve the old hugetlb successfully, >> since we did not use the new allocated hugetlb in this 2 cases. Moreover, >> moving the allocation into the free hugetlb handling branch. > > The changelog is a bit hard for me to understand. What about the > following instead? > alloc_and_dissolve_hugetlb_folio preallocates a new huge page before it > takes hugetlb_lock. In 3 out of 4 cases the page is not really used and > therefore the newly allocated page is just freed right away. This is > wasteful and it might cause pre-mature failures in those cases. > > Address that by moving the allocation down to the only case (hugetlb > page is really in the free pages pool). We need to drop hugetlb_lock > to do so and therefore need to recheck the page state after regaining > it. > > The patch is more of a cleanup than an actual fix to an existing > problem. There are no known reports about pre-mature failures.
Looks better. Thanks.
>> @@ -3075,6 +3063,24 @@ static int alloc_and_dissolve_hugetlb_folio(struct hstate *h, >> cond_resched(); >> goto retry; >> } else { >> + if (!new_folio) { >> + spin_unlock_irq(&hugetlb_lock); >> + /* >> + * Before dissolving the free hugetlb, we need to allocate >> + * a new one for the pool to remain stable. Here, we >> + * allocate the folio and 'prep' it by doing everything >> + * but actually updating counters and adding to the pool. >> + * This simplifies and let us do most of the processing >> + * under the lock. >> + */ > > This comment is not really needed anymore IMHO.
Acked.
> >> + new_folio = alloc_buddy_hugetlb_folio(h, gfp_mask, nid, >> + NULL, NULL); >> + if (!new_folio) >> + return -ENOMEM; >> + __prep_new_hugetlb_folio(h, new_folio); >> + goto retry; >> + } >> + >> /* >> * Ok, old_folio is still a genuine free hugepage. Remove it from >> * the freelist and decrease the counters. These will be >
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