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    SubjectRe: [PATCH v4 3/8] foundations of per-cgroup memory pressure controlling.
    On 10/04/2011 04:57 AM, KAMEZAWA Hiroyuki wrote:
    > On Mon, 3 Oct 2011 14:18:38 +0400
    > Glauber Costa<glommer@parallels.com> wrote:
    >
    >> This patch converts struct sock fields memory_pressure,
    >> memory_allocated, sockets_allocated, and sysctl_mem (now prot_mem)
    >> to function pointers, receiving a struct mem_cgroup parameter.
    >>
    >> enter_memory_pressure is kept the same, since all its callers
    >> have socket a context, and the kmem_cgroup can be derived from
    >> the socket itself.
    >>
    >> To keep things working, the patch convert all users of those fields
    >> to use acessor functions.
    >>
    >> In my benchmarks I didn't see a significant performance difference
    >> with this patch applied compared to a baseline (around 1 % diff, thus
    >> inside error margin).
    >>
    >> Signed-off-by: Glauber Costa<glommer@parallels.com>
    >> CC: David S. Miller<davem@davemloft.net>
    >> CC: Hiroyouki Kamezawa<kamezawa.hiroyu@jp.fujitsu.com>
    >> CC: Eric W. Biederman<ebiederm@xmission.com>
    >
    > A nitpick.
    >
    >
    >> #ifdef CONFIG_INET
    >> struct sock;
    >> +struct proto;
    >> #ifdef CONFIG_CGROUP_MEM_RES_CTLR_KMEM
    >> void sock_update_memcg(struct sock *sk);
    >> void sock_release_memcg(struct sock *sk);
    >> -
    >> +void memcg_sock_mem_alloc(struct mem_cgroup *mem, struct proto *prot,
    >> + int amt, int *parent_failure);
    >> +void memcg_sock_mem_free(struct mem_cgroup *mem, struct proto *prot, int amt);
    >> +void memcg_sockets_allocated_dec(struct mem_cgroup *mem, struct proto *prot);
    >> +void memcg_sockets_allocated_inc(struct mem_cgroup *mem, struct proto *prot);
    >> #else
    >> +/* memcontrol includes sockets.h, that includes memcontrol.h ... */
    >> +static inline void memcg_sock_mem_alloc(struct mem_cgroup *mem,
    >> + struct proto *prot, int amt,
    >> + int *parent_failure)
    >> +{
    >> +}
    >
    > In these days, at naming memory cgroup pointers, we use "memcg" instead of
    > "mem". So, could you use "memcg" for represeinting memory cgroup ?
    >
    >
    >> +
    >> +void memcg_sock_mem_alloc(struct mem_cgroup *mem, struct proto *prot,
    >> + int amt, int *parent_failure)
    >> +{
    >> + mem = parent_mem_cgroup(mem);
    >> + for (; mem != NULL; mem = parent_mem_cgroup(mem)) {
    >> + long alloc;
    >> + long *prot_mem = prot->prot_mem(mem);
    >> + /*
    >> + * Large nestings are not the common case, and stopping in the
    >> + * middle would be complicated enough, that we bill it all the
    >> + * way through the root, and if needed, unbill everything later
    >> + */
    >> + alloc = atomic_long_add_return(amt,
    >> + prot->memory_allocated(mem));
    >> + *parent_failure |= (alloc> prot_mem[2]);
    >> + }
    >> +}
    >> +EXPORT_SYMBOL(memcg_sock_mem_alloc);
    >
    > Hmm. why not using res_counter ? for reusing 'unbill' code ?
    >
    > Thanks,
    > -Kame
    >
    Well, besides the cost, we'd have atomic_t for !cgroups, and res_counter
    for cgroups. I think there is value in keeping them the same.


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