On Tue 29-08-17 11:01:50, Roman Gushchin wrote: > We've noticed a quite sensible performance overhead on some hosts > with significant network traffic when socket memory accounting > is enabled. > > Perf top shows that socket memory uncharging path is hot: > 2.13% [kernel] [k] page_counter_cancel > 1.14% [kernel] [k] __sk_mem_reduce_allocated > 1.14% [kernel] [k] _raw_spin_lock > 0.87% [kernel] [k] _raw_spin_lock_irqsave > 0.84% [kernel] [k] tcp_ack > 0.84% [kernel] [k] ixgbe_poll > 0.83% < workload > > 0.82% [kernel] [k] enqueue_entity > 0.68% [kernel] [k] __fget > 0.68% [kernel] [k] tcp_delack_timer_handler > 0.67% [kernel] [k] __schedule > 0.60% < workload > > 0.59% [kernel] [k] __inet6_lookup_established > 0.55% [kernel] [k] __switch_to > 0.55% [kernel] [k] menu_select > 0.54% libc-2.20.so [.] __memcpy_avx_unaligned > > To address this issue, the existing per-cpu stock infrastructure > can be used. > > refill_stock() can be called from mem_cgroup_uncharge_skmem() > to move charge to a per-cpu stock instead of calling atomic > page_counter_uncharge(). > > To prevent the uncontrolled growth of per-cpu stocks, > refill_stock() will explicitly drain the cached charge, > if the cached value exceeds CHARGE_BATCH. > > This allows significantly optimize the load: > 1.21% [kernel] [k] _raw_spin_lock > 1.01% [kernel] [k] ixgbe_poll > 0.92% [kernel] [k] _raw_spin_lock_irqsave > 0.90% [kernel] [k] enqueue_entity > 0.86% [kernel] [k] tcp_ack > 0.85% < workload > > 0.74% perf-11120.map [.] 0x000000000061bf24 > 0.73% [kernel] [k] __schedule > 0.67% [kernel] [k] __fget > 0.63% [kernel] [k] __inet6_lookup_established > 0.62% [kernel] [k] menu_select > 0.59% < workload > > 0.59% [kernel] [k] __switch_to > 0.57% libc-2.20.so [.] __memcpy_avx_unaligned > > Signed-off-by: Roman Gushchin <guro@xxxxxx> > Cc: Johannes Weiner <hannes@xxxxxxxxxxx> > Cc: Michal Hocko <mhocko@xxxxxxxxxx> > Cc: Vladimir Davydov <vdavydov.dev@xxxxxxxxx> > Cc: cgroups@xxxxxxxxxxxxxxx > Cc: kernel-team@xxxxxx > Cc: linux-mm@xxxxxxxxx > Cc: linux-kernel@xxxxxxxxxxxxxxx Acked-by: Michal Hocko <mhocko@xxxxxxxx> > --- > mm/memcontrol.c | 6 ++++-- > 1 file changed, 4 insertions(+), 2 deletions(-) > > diff --git a/mm/memcontrol.c b/mm/memcontrol.c > index b9cf3cf4a3d0..a69d23082abf 100644 > --- a/mm/memcontrol.c > +++ b/mm/memcontrol.c > @@ -1792,6 +1792,9 @@ static void refill_stock(struct mem_cgroup *memcg, unsigned int nr_pages) > } > stock->nr_pages += nr_pages; > > + if (stock->nr_pages > CHARGE_BATCH) > + drain_stock(stock); > + > local_irq_restore(flags); > } > > @@ -5886,8 +5889,7 @@ void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages) > > this_cpu_sub(memcg->stat->count[MEMCG_SOCK], nr_pages); > > - page_counter_uncharge(&memcg->memory, nr_pages); > - css_put_many(&memcg->css, nr_pages); > + refill_stock(memcg, nr_pages); > } > > static int __init cgroup_memory(char *s) > -- > 2.13.5 -- Michal Hocko SUSE Labs -- 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>
