Re: [PATCH v4 3/8] foundations of per-cgroup memory pressure controlling.

[Glauber Costa]

On 10/04/2011 04:57 AM, KAMEZAWA Hiroyuki wrote:
> On Mon,  3 Oct 2011 14:18:38 +0400
> Glauber Costa<glommer@xxxxxxxxxxxxx>  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@xxxxxxxxxxxxx>
> > CC: David S. Miller<davem@xxxxxxxxxxxxx>
> > CC: Hiroyouki Kamezawa<kamezawa.hiroyu@xxxxxxxxxxxxxx>
> > CC: Eric W. Biederman<ebiederm@xxxxxxxxxxxx>
>
> 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 ?
Well,

res_counters are slightly more expensive than needed here, since we need 
to clear interrupts and hold a spinlock. No particular reason besides it.


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