* [patch for-4.12] mm, thp: remove cond_resched from __collapse_huge_page_copy
@ 2017-06-19 20:43 David Rientjes
2017-06-23 13:24 ` Michal Hocko
0 siblings, 1 reply; 2+ messages in thread
From: David Rientjes @ 2017-06-19 20:43 UTC (permalink / raw)
To: Andrew Morton, Larry Finger; +Cc: Vlastimil Babka, LKML, linux-mm
This is a partial revert of commit 338a16ba1549 ("mm, thp: copying user
pages must schedule on collapse") which added a cond_resched() to
__collapse_huge_page_copy().
On x86 with CONFIG_HIGHPTE, __collapse_huge_page_copy is called in atomic
context and thus scheduling is not possible. This is only a possible
config on arm and i386.
Although need_resched has been shown to be set for over 100 jiffies while
doing the iteration in __collapse_huge_page_copy, this is better than
doing
if (in_atomic())
cond_resched()
to cover only non-CONFIG_HIGHPTE configs.
Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
Signed-off-by: David Rientjes <rientjes@google.com>
---
Note: Larry should be back as of June 17 to test if this fixes the
reported issue.
mm/khugepaged.c | 1 -
1 file changed, 1 deletion(-)
diff --git a/mm/khugepaged.c b/mm/khugepaged.c
--- a/mm/khugepaged.c
+++ b/mm/khugepaged.c
@@ -652,7 +652,6 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
spin_unlock(ptl);
free_page_and_swap_cache(src_page);
}
- cond_resched();
}
}
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^ permalink raw reply [flat|nested] 2+ messages in thread
* Re: [patch for-4.12] mm, thp: remove cond_resched from __collapse_huge_page_copy
2017-06-19 20:43 [patch for-4.12] mm, thp: remove cond_resched from __collapse_huge_page_copy David Rientjes
@ 2017-06-23 13:24 ` Michal Hocko
0 siblings, 0 replies; 2+ messages in thread
From: Michal Hocko @ 2017-06-23 13:24 UTC (permalink / raw)
To: David Rientjes
Cc: Andrew Morton, Larry Finger, Vlastimil Babka, LKML, linux-mm
On Mon 19-06-17 13:43:11, David Rientjes wrote:
> This is a partial revert of commit 338a16ba1549 ("mm, thp: copying user
> pages must schedule on collapse") which added a cond_resched() to
> __collapse_huge_page_copy().
>
> On x86 with CONFIG_HIGHPTE, __collapse_huge_page_copy is called in atomic
> context and thus scheduling is not possible. This is only a possible
> config on arm and i386.
>
> Although need_resched has been shown to be set for over 100 jiffies while
> doing the iteration in __collapse_huge_page_copy, this is better than
> doing
>
> if (in_atomic())
> cond_resched()
>
> to cover only non-CONFIG_HIGHPTE configs.
>
> Reported-by: Larry Finger <Larry.Finger@lwfinger.net>
> Signed-off-by: David Rientjes <rientjes@google.com>
Acked-by: Michal Hocko <mhocko@suse.com>
> ---
> Note: Larry should be back as of June 17 to test if this fixes the
> reported issue.
>
> mm/khugepaged.c | 1 -
> 1 file changed, 1 deletion(-)
>
> diff --git a/mm/khugepaged.c b/mm/khugepaged.c
> --- a/mm/khugepaged.c
> +++ b/mm/khugepaged.c
> @@ -652,7 +652,6 @@ static void __collapse_huge_page_copy(pte_t *pte, struct page *page,
> spin_unlock(ptl);
> free_page_and_swap_cache(src_page);
> }
> - cond_resched();
> }
> }
>
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@kvack.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
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--
Michal Hocko
SUSE Labs
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