Commit c5bb27e2 authored Mar 30, 2025 by Alexei Starovoitov Committed by Andrew Morton Apr 11, 2025

mm/page_alloc: avoid second trylock of zone->lock

spin_trylock followed by spin_lock will cause extra write cache access. 
If the lock is contended it may cause unnecessary cache line bouncing and
will execute redundant irq restore/save pair.  Therefore, check
alloc/fpi_flags first and use spin_trylock or spin_lock.

Link: https://lkml.kernel.org/r/20250331002809.94758-1-alexei.starovoitov@gmail.com


Fixes: 97769a53 ("mm, bpf: Introduce try_alloc_pages() for opportunistic page allocation")
Signed-off-by: Alexei Starovoitov <ast@kernel.org>
Suggested-by: Linus Torvalds <torvalds@linux-foundation.org>
Reviewed-by: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Acked-by: Michal Hocko <mhocko@suse.com>
Acked-by: Vlastimil Babka <vbabka@suse.cz>
Reviewed-by: Harry Yoo <harry.yoo@oracle.com>
Reviewed-by: Shakeel Butt <shakeel.butt@linux.dev>
Cc: Andrii Nakryiko <andrii@kernel.org>
Cc: Daniel Borkman <daniel@iogearbox.net>
Cc: Martin KaFai Lau <martin.lau@kernel.org>
Cc: Michal Hocko <mhocko@suse.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>

parent a84edd52

mm/page_alloc.c

+9 −6

Original line number	Diff line number	Diff line
		@@ -1400,11 +1400,12 @@ static void free_one_page(struct zone zone, struct page page,
		struct llist_head *llhead;
		unsigned long flags;

		if (!spin_trylock_irqsave(&zone->lock, flags)) {
		if (unlikely(fpi_flags & FPI_TRYLOCK)) {
		if (!spin_trylock_irqsave(&zone->lock, flags)) {
		add_page_to_zone_llist(zone, page, order);
		return;
		}
		} else {
		spin_lock_irqsave(&zone->lock, flags);
		}

		@@ -2314,9 +2315,10 @@ static int rmqueue_bulk(struct zone *zone, unsigned int order,
		unsigned long flags;
		int i;

		if (!spin_trylock_irqsave(&zone->lock, flags)) {
		if (unlikely(alloc_flags & ALLOC_TRYLOCK))
		if (unlikely(alloc_flags & ALLOC_TRYLOCK)) {
		if (!spin_trylock_irqsave(&zone->lock, flags))
		return 0;
		} else {
		spin_lock_irqsave(&zone->lock, flags);
		}
		for (i = 0; i < count; ++i) {
		@@ -2937,9 +2939,10 @@ struct page rmqueue_buddy(struct zone preferred_zone, struct zone *zone,

		do {
		page = NULL;
		if (!spin_trylock_irqsave(&zone->lock, flags)) {
		if (unlikely(alloc_flags & ALLOC_TRYLOCK))
		if (unlikely(alloc_flags & ALLOC_TRYLOCK)) {
		if (!spin_trylock_irqsave(&zone->lock, flags))
		return NULL;
		} else {
		spin_lock_irqsave(&zone->lock, flags);
		}
		if (alloc_flags & ALLOC_HIGHATOMIC)