Messages in this thread | | | Subject | Re: [External] Re: [PATCH v21 0/9] Free some vmemmap pages of HugeTLB page | From | Mike Kravetz <> | Date | Thu, 29 Apr 2021 16:19:40 -0700 |
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On 4/29/21 3:23 PM, Mike Kravetz wrote: > On 4/28/21 9:02 PM, Muchun Song wrote: >> On Thu, Apr 29, 2021 at 10:32 AM Mike Kravetz <mike.kravetz@oracle.com> wrote: >>> >>> On 4/28/21 5:26 AM, Muchun Song wrote: >>>> On Wed, Apr 28, 2021 at 7:47 AM Mike Kravetz <mike.kravetz@oracle.com> wrote: >>>>> >>>>> Thanks! I will take a look at the modifications soon. >>>>> >>>>> I applied the patches to Andrew's mmotm-2021-04-21-23-03, ran some tests and >>>>> got the following warning. We may need to special case that call to >>>>> __prep_new_huge_page/free_huge_page_vmemmap from alloc_and_dissolve_huge_page >>>>> as it is holding hugetlb lock with IRQs disabled. >>>> >>>> Good catch. Thanks Mike. I will fix it in the next version. How about this: >>>> >>>> @@ -1618,7 +1617,8 @@ static void __prep_new_huge_page(struct hstate >>>> *h, struct page *page) >>>> >>>> static void prep_new_huge_page(struct hstate *h, struct page *page, int nid) >>>> { >>>> + free_huge_page_vmemmap(h, page); >>>> __prep_new_huge_page(page); >>>> spin_lock_irq(&hugetlb_lock); >>>> __prep_account_new_huge_page(h, nid); >>>> spin_unlock_irq(&hugetlb_lock); >>>> @@ -2429,6 +2429,7 @@ static int alloc_and_dissolve_huge_page(struct >>>> hstate *h, struct page *old_page, >>>> if (!new_page) >>>> return -ENOMEM; >>>> >>>> + free_huge_page_vmemmap(h, new_page); >>>> retry: >>>> spin_lock_irq(&hugetlb_lock); >>>> if (!PageHuge(old_page)) { >>>> @@ -2489,7 +2490,7 @@ static int alloc_and_dissolve_huge_page(struct >>>> hstate *h, struct page *old_page, >>>> >>>> free_new: >>>> spin_unlock_irq(&hugetlb_lock); >>>> - __free_pages(new_page, huge_page_order(h)); >>>> + update_and_free_page(h, new_page, false); >>>> >>>> return ret; >>>> } >>>> >>>> >>> >>> Another option would be to leave the prep* routines as is and only >>> modify alloc_and_dissolve_huge_page as follows: >> >> OK. LGTM. I will use this. Thanks Mike. > > There are issues with my suggested patch below. I am occasionally > hitting the BUG that checks for page ref count being zero at put_page > time. Still do not fully understand, but I do not hit the same BUG > with your patch above. Please do not use my patch below. >
Ah! The issue is pretty obvious.
> @@ -2489,7 +2489,7 @@ static int alloc_and_dissolve_huge_page(struct hstate *h, struct page *old_page, > > free_new: > spin_unlock_irq(&hugetlb_lock); > - __free_pages(new_page, huge_page_order(h)); > + update_and_free_page(h, old_page, false);
That should of course be: update_and_free_page(h, new_page, false);
> > return ret; > } >
-- Mike Kravetz
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