From: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
IRQ context were excluded from using the Per-Cpu-Pages (PCP) lists caching
of order-0 pages in commit 374ad05ab64d ("mm, page_alloc: only use per-cpu
allocator for irq-safe requests").
This unfortunately also included excluded SoftIRQ. This hurt the performance
for the use-case of refilling DMA RX rings in softirq context.
This patch re-allow softirq context, which should be safe by disabling
BH/softirq, while accessing the list. PCP-lists access from both hard-IRQ
and NMI context must not be allowed. Peter Zijlstra says in_nmi() code
never access the page allocator, thus it should be sufficient to only test
for !in_irq().
One concern with this change is adding a BH (enable) scheduling point at
both PCP alloc and free. If further concerns are highlighted by this patch,
the result wiill be to revert 374ad05ab64d and try again at a later date
to offset the irq enable/disable overhead.
Fixes: 374ad05ab64d ("mm, page_alloc: only use per-cpu allocator for irq-safe requests")
Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 26 +++++++++++++++++---------
1 file changed, 17 insertions(+), 9 deletions(-)
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6cbde310abed..d7e986967910 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2351,9 +2351,9 @@ static void drain_local_pages_wq(struct work_struct *work)
* cpu which is allright but we also have to make sure to not move to
* a different one.
*/
- preempt_disable();
+ local_bh_disable();
drain_local_pages(NULL);
- preempt_enable();
+ local_bh_enable();
}
/*
@@ -2481,7 +2481,11 @@ void free_hot_cold_page(struct page *page, bool cold)
unsigned long pfn = page_to_pfn(page);
int migratetype;
- if (in_interrupt()) {
+ /*
+ * Exclude (hard) IRQ and NMI context from using the pcplists.
+ * But allow softirq context, via disabling BH.
+ */
+ if (in_irq() || irqs_disabled()) {
__free_pages_ok(page, 0);
return;
}
@@ -2491,7 +2495,7 @@ void free_hot_cold_page(struct page *page, bool cold)
migratetype = get_pfnblock_migratetype(page, pfn);
set_pcppage_migratetype(page, migratetype);
- preempt_disable();
+ local_bh_disable();
/*
* We only track unmovable, reclaimable and movable on pcp lists.
@@ -2522,7 +2526,7 @@ void free_hot_cold_page(struct page *page, bool cold)
}
out:
- preempt_enable();
+ local_bh_enable();
}
/*
@@ -2647,7 +2651,7 @@ static struct page *__rmqueue_pcplist(struct zone *zone, int migratetype,
{
struct page *page;
- VM_BUG_ON(in_interrupt());
+ VM_BUG_ON(in_irq() || irqs_disabled());
do {
if (list_empty(list)) {
@@ -2680,7 +2684,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
bool cold = ((gfp_flags & __GFP_COLD) != 0);
struct page *page;
- preempt_disable();
+ local_bh_disable();
pcp = &this_cpu_ptr(zone->pageset)->pcp;
list = &pcp->lists[migratetype];
page = __rmqueue_pcplist(zone, migratetype, cold, pcp, list);
@@ -2688,7 +2692,7 @@ static struct page *rmqueue_pcplist(struct zone *preferred_zone,
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
zone_statistics(preferred_zone, zone);
}
- preempt_enable();
+ local_bh_enable();
return page;
}
@@ -2704,7 +2708,11 @@ struct page *rmqueue(struct zone *preferred_zone,
unsigned long flags;
struct page *page;
- if (likely(order == 0) && !in_interrupt()) {
+ /*
+ * Exclude (hard) IRQ and NMI context from using the pcplists.
+ * But allow softirq context, via disabling BH.
+ */
+ if (likely(order == 0) && !(in_irq() || irqs_disabled()) ) {
page = rmqueue_pcplist(preferred_zone, zone, order,
gfp_flags, migratetype);
goto out;
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
