The patch titled
Subject: mm, page_alloc: re-enable softirq use of per-cpu page allocator
has been removed from the -mm tree. Its filename was
mm-page_alloc-re-enable-softirq-use-of-per-cpu-page-allocator.patch
This patch was dropped because it is obsolete
------------------------------------------------------
From: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Subject: mm, page_alloc: re-enable softirq use of per-cpu page allocator
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 will 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")
Link: http://lkml.kernel.org/r/20170410150821.vcjlz7ntabtfsumm@xxxxxxxxxxxxxxxxxxx
Signed-off-by: Jesper Dangaard Brouer <brouer@xxxxxxxxxx>
Signed-off-by: Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx>
Reported-by: Tariq Toukan <tariqt@xxxxxxxxxxxx>
Cc: Matthew Wilcox <willy@xxxxxxxxxxxxx>
Cc: Peter Zijlstra <peterz@xxxxxxxxxxxxx>
Cc: Pankaj Gupta <pagupta@xxxxxxxxxx>
Cc: Tariq Toukan <ttoukan.linux@xxxxxxxxx>
Cc: Saeed Mahameed <saeedm@xxxxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
mm/page_alloc.c | 26 +++++++++++++++++---------
1 file changed, 17 insertions(+), 9 deletions(-)
diff -puN mm/page_alloc.c~mm-page_alloc-re-enable-softirq-use-of-per-cpu-page-allocator mm/page_alloc.c
--- a/mm/page_alloc.c~mm-page_alloc-re-enable-softirq-use-of-per-cpu-page-allocator
+++ a/mm/page_alloc.c
@@ -2351,9 +2351,9 @@ static void drain_local_pages_wq(struct
* 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();
}
/*
@@ -2488,7 +2488,11 @@ void free_hot_cold_page(struct page *pag
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;
}
@@ -2498,7 +2502,7 @@ void free_hot_cold_page(struct page *pag
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.
@@ -2529,7 +2533,7 @@ void free_hot_cold_page(struct page *pag
}
out:
- preempt_enable();
+ local_bh_enable();
}
/*
@@ -2654,7 +2658,7 @@ static struct page *__rmqueue_pcplist(st
{
struct page *page;
- VM_BUG_ON(in_interrupt());
+ VM_BUG_ON(in_irq() || irqs_disabled());
do {
if (list_empty(list)) {
@@ -2687,7 +2691,7 @@ static struct page *rmqueue_pcplist(stru
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);
@@ -2695,7 +2699,7 @@ static struct page *rmqueue_pcplist(stru
__count_zid_vm_events(PGALLOC, page_zonenum(page), 1 << order);
zone_statistics(preferred_zone, zone);
}
- preempt_enable();
+ local_bh_enable();
return page;
}
@@ -2711,7 +2715,11 @@ struct page *rmqueue(struct zone *prefer
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;
_
Patches currently in -mm which might be from brouer@xxxxxxxxxx are
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