On 23/03/2017 4:51 PM, Mel Gorman wrote:
On Thu, Mar 23, 2017 at 02:43:47PM +0100, Jesper Dangaard Brouer wrote:
On Wed, 22 Mar 2017 23:40:04 +0000
Mel Gorman <mgorman@xxxxxxxxxxxxxxxxxxx> wrote:
On Wed, Mar 22, 2017 at 07:39:17PM +0200, Tariq Toukan wrote:
This modification may slow allocations from IRQ context slightly
but the
main gain from the per-cpu allocator is that it scales better for
allocations from multiple contexts. There is an implicit
assumption that
intensive allocations from IRQ contexts on multiple CPUs from a single
NUMA node are rare
Hi Mel, Jesper, and all.
This assumption contradicts regular multi-stream traffic that is naturally
handled
over close numa cores. I compared iperf TCP multistream (8 streams)
over CX4 (mlx5 driver) with kernels v4.10 (before this series) vs
kernel v4.11-rc1 (with this series).
I disabled the page-cache (recycle) mechanism to stress the page allocator,
and see a drastic degradation in BW, from 47.5 G in v4.10 to 31.4 G in
v4.11-rc1 (34% drop).
I noticed queued_spin_lock_slowpath occupies 62.87% of CPU time.
Can you get the stack trace for the spin lock slowpath to confirm it's
from IRQ context?
AFAIK allocations happen in softirq. Argh and during review I missed
that in_interrupt() also covers softirq. To Mel, can we use a in_irq()
check instead?
(p.s. just landed and got home)
Glad to hear. Thanks for your suggestion.
Not built or even boot tested. I'm unable to run tests at the moment
Thanks Mel, I will test it soon.
diff --git a/mm/page_alloc.c b/mm/page_alloc.c
index 6cbde310abed..f82225725bc1 100644
--- a/mm/page_alloc.c
+++ b/mm/page_alloc.c
@@ -2481,7 +2481,7 @@ void free_hot_cold_page(struct page *page, bool cold)
unsigned long pfn = page_to_pfn(page);
int migratetype;
- if (in_interrupt()) {
+ if (in_irq()) {
__free_pages_ok(page, 0);
return;
}
@@ -2647,7 +2647,7 @@ static struct page *__rmqueue_pcplist(struct zone *zone, int migratetype,
{
struct page *page;
- VM_BUG_ON(in_interrupt());
+ VM_BUG_ON(in_irq());
do {
if (list_empty(list)) {
@@ -2704,7 +2704,7 @@ struct page *rmqueue(struct zone *preferred_zone,
unsigned long flags;
struct page *page;
- if (likely(order == 0) && !in_interrupt()) {
+ if (likely(order == 0) && !in_irq()) {
page = rmqueue_pcplist(preferred_zone, zone, order,
gfp_flags, migratetype);
goto out;
--
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