Re: [PATCH 53 of 66] add numa awareness to hugepage allocations

Andrea Arcangeli
2010-11-30T19:03:24Z

On Tue, Nov 30, 2010 at 09:38:04AM +0900, Daisuke Nishimura wrote:
> I'm sorry if I miss something, "new_page" will be reused in !CONFIG_NUMA case
> as you say, but, in CONFIG_NUMA case, it is allocated in this function
> (collapse_huge_page()) by alloc_hugepage_vma(), and is not freed when memcg's
> charge failed.
> Actually, we do in collapse_huge_page():
> if (unlikely(!isolated)) {
> ...
> #ifdef CONFIG_NUMA
> put_page(new_page);
> #endif
> goto out;
> }
> later. I think we need a similar logic in memcg's failure path too.

Apologies, you really found a minor memleak in case of memcg
accounting failure.

diff --git a/mm/huge_memory.c b/mm/huge_memory.c
--- a/mm/huge_memory.c
+++ b/mm/huge_memory.c
@@ -1726,7 +1726,7 @@ static void collapse_huge_page(struct mm
}
#endif
if (unlikely(mem_cgroup_newpage_charge(new_page, mm, GFP_KERNEL)))
- goto out;
+ goto out_put_page;

anon_vma_lock(vma->anon_vma);

@@ -1755,10 +1755,7 @@ static void collapse_huge_page(struct mm
spin_unlock(&mm->page_table_lock);
anon_vma_unlock(vma->anon_vma);
mem_cgroup_uncharge_page(new_page);
-#ifdef CONFIG_NUMA
- put_page(new_page);
-#endif
- goto out;
+ goto out_put_page;
}

/*
@@ -1799,6 +1796,13 @@ static void collapse_huge_page(struct mm
khugepaged_pages_collapsed++;
out:
up_write(&mm->mmap_sem);
+ return;
+
+out_put_page:
+#ifdef CONFIG_NUMA
+ put_page(new_page);
+#endif
+ goto out;
}

static int khugepaged_scan_pmd(struct mm_struct *mm,

I was too optimistic that there wasn't really a bug, I thought it was
some confusion about the hpage usage that differs with numa and not
numa.

On a side note, the CONFIG_NUMA case will later change further to move
the allocation out of the mmap_sem write mode to make the fs
submitting I/O from userland and doing memory allocations in the I/O
paths happier.