From c24ad77d962c31af92f2b731dad2104cbf3fbb03 Mon Sep 17 00:00:00 2001 From: Lucas Stach Date: Thu, 14 Dec 2017 15:32:55 -0800 Subject: mm/page_alloc.c: avoid excessive IRQ disabled times in free_unref_page_list() Since commit 9cca35d42eb6 ("mm, page_alloc: enable/disable IRQs once when freeing a list of pages") we see excessive IRQ disabled times of up to 25ms on an embedded ARM system (tracing overhead included). This is due to graphics buffers being freed back to the system via release_pages(). Graphics buffers can be huge, so it's not hard to hit cases where the list of pages to free has 2048 entries. Disabling IRQs while freeing all those pages is clearly not a good idea. Introduce a batch limit, which allows IRQ servicing once every few pages. The batch count is the same as used in other parts of the MM subsystem when dealing with IRQ disabled regions. Link: http://lkml.kernel.org/r/20171207170314.4419-1-l.stach@pengutronix.de Fixes: 9cca35d42eb6 ("mm, page_alloc: enable/disable IRQs once when freeing a list of pages") Signed-off-by: Lucas Stach Acked-by: Mel Gorman Cc: Michal Hocko Cc: Vlastimil Babka Signed-off-by: Andrew Morton Signed-off-by: Linus Torvalds --- mm/page_alloc.c | 11 +++++++++++ 1 file changed, 11 insertions(+) (limited to 'mm') diff --git a/mm/page_alloc.c b/mm/page_alloc.c index 73f5d4556b3d..7e5e775e97f4 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -2684,6 +2684,7 @@ void free_unref_page_list(struct list_head *list) { struct page *page, *next; unsigned long flags, pfn; + int batch_count = 0; /* Prepare pages for freeing */ list_for_each_entry_safe(page, next, list, lru) { @@ -2700,6 +2701,16 @@ void free_unref_page_list(struct list_head *list) set_page_private(page, 0); trace_mm_page_free_batched(page); free_unref_page_commit(page, pfn); + + /* + * Guard against excessive IRQ disabled times when we get + * a large list of pages to free. + */ + if (++batch_count == SWAP_CLUSTER_MAX) { + local_irq_restore(flags); + batch_count = 0; + local_irq_save(flags); + } } local_irq_restore(flags); } -- cgit