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SubjectRe: [PATCH net-next] net, mm: avoid unnecessary memcg charge skmem
On Sat, Jun 30, 2018 at 6:09 PM, Yafang Shao <laoar.shao@gmail.com> wrote:
> In __sk_mem_raise_allocated(), if mem_cgroup_charge_skmem() return
> false, mem_cgroup_uncharge_skmem will be executed.
>
> The logic is as bellow,
> __sk_mem_raise_allocated
> ret = mem_cgroup_uncharge_skmem
> try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages);
> return false
> if (!ret)
> mem_cgroup_uncharge_skmem(sk->sk_memcg, amt);
>
> So it is unnecessary to charge if it is not forced.
>
> Signed-off-by: Yafang Shao <laoar.shao@gmail.com>
> ---
> include/linux/memcontrol.h | 3 ++-
> mm/memcontrol.c | 12 +++++++++---
> net/core/sock.c | 5 +++--
> net/ipv4/tcp_output.c | 2 +-
> 4 files changed, 15 insertions(+), 7 deletions(-)
>
> diff --git a/include/linux/memcontrol.h b/include/linux/memcontrol.h
> index 6c6fb11..56c07c9 100644
> --- a/include/linux/memcontrol.h
> +++ b/include/linux/memcontrol.h
> @@ -1160,7 +1160,8 @@ static inline void mem_cgroup_wb_stats(struct bdi_writeback *wb,
> #endif /* CONFIG_CGROUP_WRITEBACK */
>
> struct sock;
> -bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
> +bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages,
> + bool force);
> void mem_cgroup_uncharge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages);
> #ifdef CONFIG_MEMCG
> extern struct static_key_false memcg_sockets_enabled_key;
> diff --git a/mm/memcontrol.c b/mm/memcontrol.c
> index e6f0d5e..1122be2 100644
> --- a/mm/memcontrol.c
> +++ b/mm/memcontrol.c
> @@ -5929,7 +5929,8 @@ void mem_cgroup_sk_free(struct sock *sk)
> * Charges @nr_pages to @memcg. Returns %true if the charge fit within
> * @memcg's configured limit, %false if the charge had to be forced.
> */
> -bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
> +bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages,
> + bool force)
> {
> gfp_t gfp_mask = GFP_KERNEL;
>
> @@ -5940,7 +5941,10 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
> memcg->tcpmem_pressure = 0;
> return true;
> }
> - page_counter_charge(&memcg->tcpmem, nr_pages);
> +
> + if (force)
> + page_counter_charge(&memcg->tcpmem, nr_pages);
> +
> memcg->tcpmem_pressure = 1;
> return false;
> }
> @@ -5954,7 +5958,9 @@ bool mem_cgroup_charge_skmem(struct mem_cgroup *memcg, unsigned int nr_pages)
> if (try_charge(memcg, gfp_mask, nr_pages) == 0)
> return true;
>
> - try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages);
> + if (force)
> + try_charge(memcg, gfp_mask|__GFP_NOFAIL, nr_pages);
> +
> return false;
> }
>
> diff --git a/net/core/sock.c b/net/core/sock.c
> index bcc4182..148a840 100644
> --- a/net/core/sock.c
> +++ b/net/core/sock.c
> @@ -2401,9 +2401,10 @@ int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)
> {
> struct proto *prot = sk->sk_prot;
> long allocated = sk_memory_allocated_add(sk, amt);
> + bool charged = false;
>
> if (mem_cgroup_sockets_enabled && sk->sk_memcg &&
> - !mem_cgroup_charge_skmem(sk->sk_memcg, amt))
> + !(charged = mem_cgroup_charge_skmem(sk->sk_memcg, amt, false)))
> goto suppress_allocation;
>
> /* Under limit. */
> @@ -2465,7 +2466,7 @@ int __sk_mem_raise_allocated(struct sock *sk, int size, int amt, int kind)
>
> sk_memory_allocated_sub(sk, amt);
>
> - if (mem_cgroup_sockets_enabled && sk->sk_memcg)
> + if (mem_cgroup_sockets_enabled && sk->sk_memcg && charged)
> mem_cgroup_uncharge_skmem(sk->sk_memcg, amt);
>
> return 0;
> diff --git a/net/ipv4/tcp_output.c b/net/ipv4/tcp_output.c
> index f8f6129..9b741d4 100644
> --- a/net/ipv4/tcp_output.c
> +++ b/net/ipv4/tcp_output.c
> @@ -3014,7 +3014,7 @@ void sk_forced_mem_schedule(struct sock *sk, int size)
> sk_memory_allocated_add(sk, amt);
>
> if (mem_cgroup_sockets_enabled && sk->sk_memcg)
> - mem_cgroup_charge_skmem(sk->sk_memcg, amt);
> + mem_cgroup_charge_skmem(sk->sk_memcg, amt, true);
> }
>
> /* Send a FIN. The caller locks the socket for us.
> --
> 1.8.3.1
>

Pls. ignore this patch.

Sorry about the noise.

Thanks
Yafang

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