[Devel] [PATCH RH8] mm, page_alloc: drop should_suppress_show_mem

[Vasily Averin]

should_suppress_show_mem() was introduced to reduce the overhead of
show_mem on large NUMA systems.  Things have changed since then though.
Namely c78e93630d15 ("mm: do not walk all of system memory during
show_mem") has reduced the overhead considerably.

Moreover warn_alloc_show_mem clears SHOW_MEM_FILTER_NODES when called from
the IRQ context already so we are not printing per node stats.

Remove should_suppress_show_mem because we are losing potentially
interesting information about allocation failures.  We have seen a bug
report where system gets unresponsive under memory pressure and there is
only

kernel: [2032243.696888] qlge 0000:8b:00.1 ql1: Could not get a page chunk, i=8, clean_idx =200 .
kernel: [2032243.710725] swapper/7: page allocation failure: order:1, mode:0x1084120(GFP_ATOMIC|__GFP_COLD|__GFP_COMP)

without an additional information for debugging.  It would be great to see
the state of the page allocator at the moment.

Link: http://lkml.kernel.org/r/20180907114334.7088-1-mhocko@kernel.org
Signed-off-by: Michal Hocko <mhocko at suse.com>
Acked-by: Vlastimil Babka <vbabka at suse.cz>
Cc: David Rientjes <rientjes at google.com>
Cc: Mel Gorman <mgorman at techsingularity.net>
Signed-off-by: Andrew Morton <akpm at linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds at linux-foundation.org>
(cherry picked from commit 2c029a1ea3aac296cd5b47584a579defcc4b4aa0)
taken from vz7 commit efa5c397b9d7
Signed-off-by: Vasily Averin <vvs at virtuozzo.com>
---
 mm/page_alloc.c | 16 +---------------
 1 file changed, 1 insertion(+), 15 deletions(-)

diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 548c4d087664..44bf30817a28 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -3489,26 +3489,12 @@ get_page_from_freelist(gfp_t gfp_mask, unsigned int order, int alloc_flags,
 	return NULL;
 }
 
-/*
- * Large machines with many possible nodes should not always dump per-node
- * meminfo in irq context.
- */
-static inline bool should_suppress_show_mem(void)
-{
-	bool ret = false;
-
-#if NODES_SHIFT > 8
-	ret = in_interrupt();
-#endif
-	return ret;
-}
-
 static void warn_alloc_show_mem(gfp_t gfp_mask, nodemask_t *nodemask)
 {
 	unsigned int filter = SHOW_MEM_FILTER_NODES;
 	static DEFINE_RATELIMIT_STATE(show_mem_rs, HZ, 1);
 
-	if (should_suppress_show_mem() || !__ratelimit(&show_mem_rs))
+	if (!__ratelimit(&show_mem_rs))
 		return;
 
 	/*
-- 
2.25.1