Re: [PATCH] mm: memcontrol: use per-cpu stocks for socket memory uncharging

Roman Gushchin
2017-08-30T10:57:19Z

On Tue, Aug 29, 2017 at 03:26:21PM -0400, Johannes Weiner wrote:
> On Tue, Aug 29, 2017 at 11:01:50AM +0100, 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-b10kYP2dOMg@public.gmane.org>
> > Cc: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
> > Cc: Michal Hocko <mhocko-DgEjT+Ai2ygdnm+yROfE0A@public.gmane.org>
> > Cc: Vladimir Davydov <vdavydov.dev-Re5JQEeQqe8AvxtiuMwx3w@public.gmane.org>
> > Cc: cgroups-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
> > Cc: kernel-team-b10kYP2dOMg@public.gmane.org
> > Cc: linux-mm-Bw31MaZKKs3YtjvyW6yDsg@public.gmane.org
> > Cc: linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org
>
> Acked-by: Johannes Weiner <hannes-druUgvl0LCNAfugRpC6u6w@public.gmane.org>
>
> Neat!

Hi, Andrew!

Can you, please, pull this patch?

Thank you!

Roman