[patch 124/131] mm, sparse: do not swamp log with huge vmemmap allocation failures

[patch 124/131] mm, sparse: do not swamp log with huge vmemmap allocation failures

[akpm]

From: Michal Hocko <mhocko@suse.com>
Subject: mm, sparse: do not swamp log with huge vmemmap allocation failures

While doing memory hotplug tests under heavy memory pressure we have
noticed too many page allocation failures when allocating vmemmap memmap
backed by huge page

[146792.281354] kworker/u3072:1: page allocation failure: order:9, mode:0x24084c0(GFP_KERNEL|__GFP_REPEAT|__GFP_ZERO)
[...]
[146792.281394] Call Trace:
[146792.281430]  [<ffffffff81019a99>] dump_trace+0x59/0x310
[146792.281436]  [<ffffffff81019e3a>] show_stack_log_lvl+0xea/0x170
[146792.281440]  [<ffffffff8101abc1>] show_stack+0x21/0x40
[146792.281448]  [<ffffffff8130f040>] dump_stack+0x5c/0x7c
[146792.281464]  [<ffffffff8118c982>] warn_alloc_failed+0xe2/0x150
[146792.281471]  [<ffffffff8118cddd>] __alloc_pages_nodemask+0x3ed/0xb20
[146792.281489]  [<ffffffff811d3aaf>] alloc_pages_current+0x7f/0x100
[146792.281503]  [<ffffffff815dfa2c>] vmemmap_alloc_block+0x79/0xb6
[146792.281510]  [<ffffffff815dfbd3>] __vmemmap_alloc_block_buf+0x136/0x145
[146792.281524]  [<ffffffff815dd0c5>] vmemmap_populate+0xd2/0x2b9
[146792.281529]  [<ffffffff815dffd9>] sparse_mem_map_populate+0x23/0x30
[146792.281532]  [<ffffffff815df88d>] sparse_add_one_section+0x68/0x18e
[146792.281537]  [<ffffffff815d9f5a>] __add_pages+0x10a/0x1d0
[146792.281553]  [<ffffffff8106249a>] arch_add_memory+0x4a/0xc0
[146792.281559]  [<ffffffff815da1f9>] add_memory_resource+0x89/0x160
[146792.281564]  [<ffffffff815da33d>] add_memory+0x6d/0xd0
[146792.281585]  [<ffffffff813d36c4>] acpi_memory_device_add+0x181/0x251
[146792.281597]  [<ffffffff813946e5>] acpi_bus_attach+0xfd/0x19b
[146792.281602]  [<ffffffff81394866>] acpi_bus_scan+0x59/0x69
[146792.281604]  [<ffffffff813949de>] acpi_device_hotplug+0xd2/0x41f
[146792.281608]  [<ffffffff8138db67>] acpi_hotplug_work_fn+0x1a/0x23
[146792.281623]  [<ffffffff81093cee>] process_one_work+0x14e/0x410
[146792.281630]  [<ffffffff81094546>] worker_thread+0x116/0x490
[146792.281637]  [<ffffffff810999ed>] kthread+0xbd/0xe0
[146792.281651]  [<ffffffff815e4e7f>] ret_from_fork+0x3f/0x70

and we do see many of those because essentially every allocation fails for
each memory section.  This is an excessive way to tell the user that there
is nothing to really worry about because we do have a fallback mechanism
to use base pages.  The only downside might be a performance degradation
due to TLB pressure.

This patch changes vmemmap_alloc_block() to use __GFP_NOWARN and warn
explicitly once on the first allocation failure.  This will reduce the
noise in the kernel log considerably, while we still have an indication
that a performance might be impacted.

[mhocko@kernel.org: forgot to git add the follow up fix]
  Link: http://lkml.kernel.org/r/20171107090635.c27thtse2lchjgvb@dhcp22.suse.cz
Link: http://lkml.kernel.org/r/20171106092228.31098-1-mhocko@kernel.org
Signed-off-by: Johannes Weiner <hannes@cmpxchg.org>
Signed-off-by: Michal Hocko <mhocko@suse.com>
Cc: Joe Perches <joe@perches.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Cc: Khalid Aziz <khalid.aziz@oracle.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
---

 arch/x86/mm/init_64.c |    1 -
 mm/sparse-vmemmap.c   |   12 ++++++++++--
 2 files changed, 10 insertions(+), 3 deletions(-)

diff -puN arch/x86/mm/init_64.c~mm-sparse-do-not-swamp-log-with-huge-vmemmap-allocation-failures arch/x86/mm/init_64.c
--- a/arch/x86/mm/init_64.c~mm-sparse-do-not-swamp-log-with-huge-vmemmap-allocation-failures
+++ a/arch/x86/mm/init_64.c
@@ -1405,7 +1405,6 @@ static int __meminit vmemmap_populate_hu
 			vmemmap_verify((pte_t *)pmd, node, addr, next);
 			continue;
 		}
-		pr_warn_once("vmemmap: falling back to regular page backing\n");
 		if (vmemmap_populate_basepages(addr, next, node))
 			return -ENOMEM;
 	}
diff -puN mm/sparse-vmemmap.c~mm-sparse-do-not-swamp-log-with-huge-vmemmap-allocation-failures mm/sparse-vmemmap.c
--- a/mm/sparse-vmemmap.c~mm-sparse-do-not-swamp-log-with-huge-vmemmap-allocation-failures
+++ a/mm/sparse-vmemmap.c
@@ -53,12 +53,20 @@ void * __meminit vmemmap_alloc_block(uns
 {
 	/* If the main allocator is up use that, fallback to bootmem. */
 	if (slab_is_available()) {
+		gfp_t gfp_mask = GFP_KERNEL|__GFP_RETRY_MAYFAIL|__GFP_NOWARN;
+		int order = get_order(size);
+		static bool warned;
 		struct page *page;
 
-		page = alloc_pages_node(node, GFP_KERNEL | __GFP_RETRY_MAYFAIL,
-					get_order(size));
+		page = alloc_pages_node(node, gfp_mask, order);
 		if (page)
 			return page_address(page);
+
+		if (!warned) {
+			warn_alloc(gfp_mask & ~__GFP_NOWARN, NULL,
+				   "vmemmap alloc failure: order:%u", order);
+			warned = true;
+		}
 		return NULL;
 	} else
 		return __earlyonly_bootmem_alloc(node, size, size,
_