Message ID | 20220708053653.964464-2-naoya.horiguchi@linux.dev (mailing list archive) |
---|---|
State | New |
Headers | show |
Series | mm, hwpoison: enable 1GB hugepage support (v5) | expand |
On 2022/7/8 13:36, Naoya Horiguchi wrote: > From: Naoya Horiguchi <naoya.horiguchi@nec.com> > > I found a weird state of 1GB hugepage pool, caused by the following > procedure: > > - run a process reserving all free 1GB hugepages, > - shrink free 1GB hugepage pool to zero (i.e. writing 0 to > /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages), then > - kill the reserving process. > > , then all the hugepages are free *and* surplus at the same time. > > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/nr_hugepages > 3 > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/free_hugepages > 3 > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/resv_hugepages > 0 > $ cat /sys/kernel/mm/hugepages/hugepages-1048576kB/surplus_hugepages > 3 > > This state is resolved by reserving and allocating the pages then > freeing them again, so this seems not to result in serious problem. > But it's a little surprising (shrinking pool suddenly fails). > > This behavior is caused by hstate_is_gigantic() check in > return_unused_surplus_pages(). This was introduced so long ago in 2008 > by commit aa888a74977a ("hugetlb: support larger than MAX_ORDER"), and > at that time the gigantic pages were not supposed to be allocated/freed > at run-time. Now kernel can support runtime allocation/free, so let's > check gigantic_page_runtime_supported() together. > > Signed-off-by: Naoya Horiguchi <naoya.horiguchi@nec.com> Looks good to me. Thanks. Reviewed-by: Miaohe Lin <linmiaohe@huawei.com>
diff --git a/mm/hugetlb.c b/mm/hugetlb.c index a4506ed1f1db..cf8ccee7654c 100644 --- a/mm/hugetlb.c +++ b/mm/hugetlb.c @@ -2432,8 +2432,7 @@ static void return_unused_surplus_pages(struct hstate *h, /* Uncommit the reservation */ h->resv_huge_pages -= unused_resv_pages; - /* Cannot return gigantic pages currently */ - if (hstate_is_gigantic(h)) + if (hstate_is_gigantic(h) && !gigantic_page_runtime_supported()) goto out; /*