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()?
