The patch titled
Subject: mm/page_alloc: let GFP_ATOMIC order-0 allocs access highatomic reserves
has been added to the -mm mm-unstable branch. Its filename is
mm-page_alloc-let-gfp_atomic-order-0-allocs-access-highatomic-reserves.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/mm-page_alloc-let-gfp_atomic-order-0-allocs-access-highatomic-reserves.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Matt Fleming <mfleming@xxxxxxxxxxxxxx>
Subject: mm/page_alloc: let GFP_ATOMIC order-0 allocs access highatomic reserves
Date: Fri, 11 Oct 2024 13:07:37 +0100
Under memory pressure it's possible for GFP_ATOMIC order-0 allocations to
fail even though free pages are available in the highatomic reserves.
GFP_ATOMIC allocations cannot trigger unreserve_highatomic_pageblock()
since it's only run from reclaim.
Given that such allocations will pass the watermarks in
__zone_watermark_unusable_free(), it makes sense to fallback to highatomic
reserves the same way that ALLOC_OOM can.
This fixes order-0 page allocation failures observed on Cloudflare's
fleet when handling network packets:
kswapd1: page allocation failure: order:0, mode:0x820(GFP_ATOMIC),
nodemask=(null),cpuset=/,mems_allowed=0-7
CPU: 10 PID: 696 Comm: kswapd1 Kdump: loaded Tainted: G O 6.6.43-CUSTOM #1
Hardware name: MACHINE
Call Trace:
<IRQ>
dump_stack_lvl+0x3c/0x50
warn_alloc+0x13a/0x1c0
__alloc_pages_slowpath.constprop.0+0xc9d/0xd10
__alloc_pages+0x327/0x340
__napi_alloc_skb+0x16d/0x1f0
bnxt_rx_page_skb+0x96/0x1b0 [bnxt_en]
bnxt_rx_pkt+0x201/0x15e0 [bnxt_en]
__bnxt_poll_work+0x156/0x2b0 [bnxt_en]
bnxt_poll+0xd9/0x1c0 [bnxt_en]
__napi_poll+0x2b/0x1b0
bpf_trampoline_6442524138+0x7d/0x1000
__napi_poll+0x5/0x1b0
net_rx_action+0x342/0x740
handle_softirqs+0xcf/0x2b0
irq_exit_rcu+0x6c/0x90
sysvec_apic_timer_interrupt+0x72/0x90
</IRQ>
Link: https://lkml.kernel.org/r/20241011120737.3300370-1-matt@xxxxxxxxxxxxxxxx
Link: https://lore.kernel.org/all/CAGis_TWzSu=P7QJmjD58WWiu3zjMTVKSzdOwWE8ORaGytzWJwQ@xxxxxxxxxxxxxx/
Signed-off-by: Matt Fleming <mfleming@xxxxxxxxxxxxxx>
Suggested-by: Vlastimil Babka <vbabka@xxxxxxx>
Cc: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 2 +-
1 file changed, 1 insertion(+), 1 deletion(-)
--- a/mm/page_alloc.c~mm-page_alloc-let-gfp_atomic-order-0-allocs-access-highatomic-reserves
+++ a/mm/page_alloc.c
@@ -2898,7 +2898,7 @@ struct page *rmqueue_buddy(struct zone *
* failing a high-order atomic allocation in the
* future.
*/
- if (!page && (alloc_flags & ALLOC_OOM))
+ if (!page && (alloc_flags & (ALLOC_OOM|ALLOC_NON_BLOCK)))
page = __rmqueue_smallest(zone, order, MIGRATE_HIGHATOMIC);
if (!page) {
_
Patches currently in -mm which might be from mfleming@xxxxxxxxxxxxxx are
mm-page_alloc-let-gfp_atomic-order-0-allocs-access-highatomic-reserves.patch
