On 04/15/2016 11:07 AM, Mel Gorman wrote:
There is a debugging check for callers that specify __GFP_DIRECT_RECLAIM from a context that cannot sleep. Triggering this is almost certainly a bug but it's also overhead in the fast path.
For CONFIG_DEBUG_ATOMIC_SLEEP, enabling is asking for the overhead. But for CONFIG_PREEMPT_VOLUNTARY which turns it into _cond_resched(), I guess it's not.
Move the check to the slow path. It'll be harder to trigger as it'll only be checked when watermarks are depleted but it'll also only be checked in a path that can sleep.
Hmm what about zone_reclaim_mode=1, should the check be also duplicated to that part of get_page_from_freelist()?
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> --- mm/page_alloc.c | 4 ++-- 1 file changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 21aaef6ddd7a..9ef2f4ab9ca5 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -3176,6 +3176,8 @@ __alloc_pages_slowpath(gfp_t gfp_mask, unsigned int order, return NULL; } + might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM); + /* * We also sanity check to catch abuse of atomic reserves being used by * callers that are not in atomic context. @@ -3369,8 +3371,6 @@ __alloc_pages_nodemask(gfp_t gfp_mask, unsigned int order, lockdep_trace_alloc(gfp_mask); - might_sleep_if(gfp_mask & __GFP_DIRECT_RECLAIM); - if (should_fail_alloc_page(gfp_mask, order)) return NULL;
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