Cliff Wickman <cpw@xxxxxxx> writes:
> From: Cliff Wickman <cpw@xxxxxxx>
>
> Gentlemen,
> I see that you all have done maintenance on mm/hugetlb.c, so I'm hoping one
> or two of you could comment on a problem and proposed fix.
>
>
> I am seeing list corruption occurring from within gather_surplus_pages()
> (mm/hugetlb.c). The problem occurs under a heavy load, and seems to be
> because this function drops the hugetlb_lock.
>
> I have CONFIG_DEBUG_LIST=y, and am running an MPI application with 64 threads
> and a library that creates a large heap of hugetlbfs pages for it.
>
> The below patch fixes the problem.
> The gist of this patch is that gather_surplus_pages() does not have to drop
> the lock if alloc_buddy_huge_page() is told whether the lock is
> already held.
But you didn't explain the corruption details right ? What cause the
corruption ? It would be nice to document that in the commit.
>
> But I may be missing some reason why gather_surplus_pages() is unlocking and
> locking the hugetlb_lock several times (besides around the allocator).
>
> Could you take a look and advise?
>
> Signed-off-by: Cliff Wickman <cpw@xxxxxxx>
> ---
> mm/hugetlb.c | 28 +++++++++++++++++-----------
> 1 file changed, 17 insertions(+), 11 deletions(-)
>
> Index: linux/mm/hugetlb.c
> ===================================================================
> --- linux.orig/mm/hugetlb.c
> +++ linux/mm/hugetlb.c
> @@ -747,7 +747,9 @@ static int free_pool_huge_page(struct hs
> return ret;
> }
>
> -static struct page *alloc_buddy_huge_page(struct hstate *h, int nid)
> +/* already_locked means the caller has already locked hugetlb_lock */
> +static struct page *alloc_buddy_huge_page(struct hstate *h, int nid,
> + int already_locked)
> {
Why ? Why can't we always call this with lock held ?
> struct page *page;
> unsigned int r_nid;
> @@ -778,7 +780,8 @@ static struct page *alloc_buddy_huge_pag
> * the node values until we've gotten the hugepage and only the
-aneesh
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>