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 <g...@fb.com> > > Cc: Johannes Weiner <han...@cmpxchg.org> > > Cc: Michal Hocko <mho...@kernel.org> > > Cc: Vladimir Davydov <vdavydov....@gmail.com> > > Cc: cgro...@vger.kernel.org > > Cc: kernel-t...@fb.com > > Cc: linux...@kvack.org > > Cc: linux-kernel@vger.kernel.org > > Acked-by: Johannes Weiner <han...@cmpxchg.org> > > Neat! > > As far as other types of pages go: page cache and anon are already > batched pretty well, but I think kmem might benefit from this > too. Have you considered using the stock in memcg_kmem_uncharge()?
Good idea! I'll try to find an appropriate testcase and check if it really brings any benefits. If so, I'll master a patch. Thanks!
