Subject: Re: [PATCH] per-cgroup tcp buffer limitation

From: Glauber Costa <[email-masked]>
Date: Tue, 6 Sep 2011 12:28:04 -0300

On 09/06/2011 07:00 AM, KAMEZAWA Hiroyuki wrote:
> On Mon,  5 Sep 2011 23:35:56 -0300
> Glauber Costa<[email-masked]>  wrote:
>
>> This patch introduces per-cgroup tcp buffers limitation. This allows
>> sysadmins to specify a maximum amount of kernel memory that
>> tcp connections can use at any point in time. TCP is the main interest
>> in this work, but extending it to other protocols would be easy.
>>
>> It piggybacks in the memory control mechanism already present in
>> /proc/sys/net/ipv4/tcp_mem. There is a soft limit, and a hard limit,
>> that will suppress allocation when reached. For each cgroup, however,
>> the file kmem.tcp_maxmem will be used to cap those values.
>>
>> The usage I have in mind here is containers. Each container will
>> define its own values for soft and hard limits, but none of them will
>> be possibly bigger than the value the box' sysadmin specified from
>> the outside.
>>
>> To test for any performance impacts of this patch, I used netperf's
>> TCP_RR benchmark on localhost, so we can have both recv and snd in action.
>>
>> Command line used was ./src/netperf -t TCP_RR -H localhost, and the
>> results:
>>
>> Without the patch
>> =================
>>
>> Socket Size   Request  Resp.   Elapsed  Trans.
>> Send   Recv   Size     Size    Time     Rate
>> bytes  Bytes  bytes    bytes   secs.    per sec
>>
>> 16384  87380  1        1       10.00    26996.35
>> 16384  87380
>>
>> With the patch
>> ===============
>>
>> Local /Remote
>> Socket Size   Request  Resp.   Elapsed  Trans.
>> Send   Recv   Size     Size    Time     Rate
>> bytes  Bytes  bytes    bytes   secs.    per sec
>>
>> 16384  87380  1        1       10.00    27291.86
>> 16384  87380
>>
>> The difference is within a one-percent range.
>>
>> Nesting cgroups doesn't seem to be the dominating factor as well,
>> with nestings up to 10 levels not showing a significant performance
>> difference.
>>
>> Signed-off-by: Glauber Costa<[email-masked]>
>> CC: David S. Miller<[email-masked]>
>> CC: Hiroyouki Kamezawa<[email-masked]>
>> CC: Eric W. Biederman<[email-masked]>
>> ---
>>   crypto/af_alg.c               |    7 ++-
>>   include/linux/cgroup_subsys.h |    4 +
>>   include/net/netns/ipv4.h      |    1 +
>>   include/net/sock.h            |   66 +++++++++++++++-
>>   include/net/tcp.h             |   12 ++-
>>   include/net/udp.h             |    3 +-
>>   include/trace/events/sock.h   |   10 +-
>>   init/Kconfig                  |   11 +++
>>   mm/Makefile                   |    1 +
>>   net/core/sock.c               |  136 +++++++++++++++++++++++++++-------
>>   net/decnet/af_decnet.c        |   21 +++++-
>>   net/ipv4/proc.c               |    8 +-
>>   net/ipv4/sysctl_net_ipv4.c    |   59 +++++++++++++--
>>   net/ipv4/tcp.c                |  164 +++++++++++++++++++++++++++++++++++-----
>>   net/ipv4/tcp_input.c          |   17 ++--
>>   net/ipv4/tcp_ipv4.c           |   27 +++++--
>>   net/ipv4/tcp_output.c         |    2 +-
>>   net/ipv4/tcp_timer.c          |    2 +-
>>   net/ipv4/udp.c                |   20 ++++-
>>   net/ipv6/tcp_ipv6.c           |   16 +++-
>>   net/ipv6/udp.c                |    4 +-
>>   net/sctp/socket.c             |   35 +++++++--
>>   22 files changed, 514 insertions(+), 112 deletions(-)
>
> Hmm...could you please devide patches into a few patches ?
>
> If I was you, I'll devide the patches into
>
>   - Kconfig/Makefile/kmem_cgroup.c skelton.
>   - changes to struct sock and macro definition
>   - hooks to tcp.
>   - hooks to udp
>   - hooks to sctp

Sure, I can do it.

> And why not including mm/kmem_cgroup.c ?
Because I am an idiot and forgot to git add.

>
> some comments below.
>
>
>>
>> diff --git a/crypto/af_alg.c b/crypto/af_alg.c
>> index ac33d5f..df168d8 100644
>> --- a/crypto/af_alg.c
>> +++ b/crypto/af_alg.c
>> @@ -29,10 +29,15 @@ struct alg_type_list {
>>
>>   static atomic_long_t alg_memory_allocated;
>>
>> +static atomic_long_t *memory_allocated_alg(struct kmem_cgroup *sg)
>> +{
>> +	return&alg_memory_allocated;
>> +}
>> +
>>   static struct proto alg_proto = {
>>   	.name			= "ALG",
>>   	.owner			= THIS_MODULE,
>> -	.memory_allocated	=&alg_memory_allocated,
>> +	.memory_allocated	= memory_allocated_alg,
>>   	.obj_size		= sizeof(struct alg_sock),
>>   };
>>
>> diff --git a/include/linux/cgroup_subsys.h b/include/linux/cgroup_subsys.h
>> index ac663c1..363b8e8 100644
>> --- a/include/linux/cgroup_subsys.h
>> +++ b/include/linux/cgroup_subsys.h
>> @@ -35,6 +35,10 @@ SUBSYS(cpuacct)
>>   SUBSYS(mem_cgroup)
>>   #endif
>>
>> +#ifdef CONFIG_CGROUP_KMEM
>> +SUBSYS(kmem)
>> +#endif
>> +
>>   /* */
>>
>>   #ifdef CONFIG_CGROUP_DEVICE
>> diff --git a/include/net/netns/ipv4.h b/include/net/netns/ipv4.h
>> index d786b4f..bbd023a 100644
>> --- a/include/net/netns/ipv4.h
>> +++ b/include/net/netns/ipv4.h
>> @@ -55,6 +55,7 @@ struct netns_ipv4 {
>>   	int current_rt_cache_rebuild_count;
>>
>>   	unsigned int sysctl_ping_group_range[2];
>> +	long sysctl_tcp_mem[3];
>>
>>   	atomic_t rt_genid;
>>   	atomic_t dev_addr_genid;
>> diff --git a/include/net/sock.h b/include/net/sock.h
>> index 8e4062f..e085148 100644
>> --- a/include/net/sock.h
>> +++ b/include/net/sock.h
>> @@ -62,7 +62,9 @@
>>   #include<linux/atomic.h>
>>   #include<net/dst.h>
>>   #include<net/checksum.h>
>> +#include<linux/kmem_cgroup.h>
>>
>> +int sockets_populate(struct cgroup_subsys *ss, struct cgroup *cgrp);
>>   /*
>>    * This structure really needs to be cleaned up.
>>    * Most of it is for TCP, and not used by any of
>> @@ -339,6 +341,7 @@ struct sock {
>>   #endif
>>   	__u32			sk_mark;
>>   	u32			sk_classid;
>> +	struct kmem_cgroup	*sk_cgrp;
>>   	void			(*sk_state_change)(struct sock *sk);
>>   	void			(*sk_data_ready)(struct sock *sk, int bytes);
>>   	void			(*sk_write_space)(struct sock *sk);
>> @@ -786,16 +789,21 @@ struct proto {
>>
>>   	/* Memory pressure */
>>   	void			(*enter_memory_pressure)(struct sock *sk);
>> -	atomic_long_t		*memory_allocated;	/* Current allocated memory. */
>> -	struct percpu_counter	*sockets_allocated;	/* Current number of sockets. */
>> +	/* Current allocated memory. */
>> +	atomic_long_t		*(*memory_allocated)(struct kmem_cgroup *sg);
>> +	/* Current number of sockets. */
>> +	struct percpu_counter	*(*sockets_allocated)(struct kmem_cgroup *sg);
>> +
>> +	int			(*init_cgroup)(struct cgroup *cgrp,
>> +					       struct cgroup_subsys *ss);
>>   	/*
>>   	 * Pressure flag: try to collapse.
>>   	 * Technical note: it is used by multiple contexts non atomically.
>>   	 * All the __sk_mem_schedule() is of this nature: accounting
>>   	 * is strict, actions are advisory and have some latency.
>>   	 */
>> -	int			*memory_pressure;
>> -	long			*sysctl_mem;
>> +	int			*(*memory_pressure)(struct kmem_cgroup *sg);
>> +	long			*(*prot_mem)(struct kmem_cgroup *sg);
>
> Hmm. Socket interface callbacks doesn't have documentation ?
> Adding explanation in Documenation is better, isn't it ?

Okay, sure thing.

>
>>   	int			*sysctl_wmem;
>>   	int			*sysctl_rmem;
>>   	int			max_header;
>> @@ -826,6 +834,56 @@ struct proto {
>>   #endif
>>   };
>>
>> +#define sk_memory_pressure(sk)						\
>> +({									\
>> +	int *__ret = NULL;						\
>> +	if ((sk)->sk_prot->memory_pressure)				\
>> +		__ret = (sk)->sk_prot->memory_pressure(sk->sk_cgrp);	\
>> +	__ret;								\
>> +})
>> +
>> +#define sk_sockets_allocated(sk)				\
>> +({								\
>> +	struct percpu_counter *__p;				\
>> +	__p = (sk)->sk_prot->sockets_allocated(sk->sk_cgrp);	\
>> +	__p;							\
>> +})
>> +
>> +#define sk_memory_allocated(sk)					\
>> +({								\
>> +	atomic_long_t *__mem;					\
>> +	__mem = (sk)->sk_prot->memory_allocated(sk->sk_cgrp);	\
>> +	__mem;							\
>> +})
>> +
>> +#define sk_prot_mem(sk)						\
>> +({								\
>> +	long *__mem = (sk)->sk_prot->prot_mem(sk->sk_cgrp);	\
>> +	__mem;							\
>> +})
>> +
>> +#define sg_memory_pressure(prot, sg)				\
>> +({								\
>> +	int *__ret = NULL;					\
>> +	if (prot->memory_pressure)				\
>> +		__ret = (prot)->memory_pressure(sg);		\
>> +	__ret;							\
>> +})
>> +
>> +#define sg_memory_allocated(prot, sg)				\
>> +({								\
>> +	atomic_long_t *__mem;					\
>> +	__mem = (prot)->memory_allocated(sg);			\
>> +	__mem;							\
>> +})
>> +
>> +#define sg_sockets_allocated(prot, sg)				\
>> +({								\
>> +	struct percpu_counter *__p;				\
>> +	__p = (prot)->sockets_allocated(sg);			\
>> +	__p;							\
>> +})
>> +
>
> All functions are worth to be inlined ?
Using the law of minimum disruption, I wanted to make them all
valid left values for any expressions, that's why it is this way.
I see that below, you suggest using things like 
sg_sockets_allocated_inc() , dec() and read(). I prefer them to be 
lvalues, but I am fine with either.

>
>
>>   extern int proto_register(struct proto *prot, int alloc_slab);
>>   extern void proto_unregister(struct proto *prot);
>>
>> diff --git a/include/net/tcp.h b/include/net/tcp.h
>> index 149a415..8e1ec4a 100644
>> --- a/include/net/tcp.h
>> +++ b/include/net/tcp.h
>> @@ -230,7 +230,6 @@ extern int sysctl_tcp_fack;
>>   extern int sysctl_tcp_reordering;
>>   extern int sysctl_tcp_ecn;
>>   extern int sysctl_tcp_dsack;
>> -extern long sysctl_tcp_mem[3];
>>   extern int sysctl_tcp_wmem[3];
>>   extern int sysctl_tcp_rmem[3];
>>   extern int sysctl_tcp_app_win;
>> @@ -253,9 +252,12 @@ extern int sysctl_tcp_cookie_size;
>>   extern int sysctl_tcp_thin_linear_timeouts;
>>   extern int sysctl_tcp_thin_dupack;
>>
>> -extern atomic_long_t tcp_memory_allocated;
>> -extern struct percpu_counter tcp_sockets_allocated;
>> -extern int tcp_memory_pressure;
>> +struct kmem_cgroup;
>> +extern long *tcp_sysctl_mem(struct kmem_cgroup *sg);
>> +struct percpu_counter *sockets_allocated_tcp(struct kmem_cgroup *sg);
>> +int *memory_pressure_tcp(struct kmem_cgroup *sg);
>> +int tcp_init_cgroup(struct cgroup *cgrp, struct cgroup_subsys *ss);
>> +atomic_long_t *memory_allocated_tcp(struct kmem_cgroup *sg);
>>
>>   /*
>>    * The next routines deal with comparing 32 bit unsigned ints
>> @@ -286,7 +288,7 @@ static inline bool tcp_too_many_orphans(struct sock *sk, int shift)
>>   	}
>>
>>   	if (sk->sk_wmem_queued>  SOCK_MIN_SNDBUF&&
>> -	    atomic_long_read(&tcp_memory_allocated)>  sysctl_tcp_mem[2])
>> +	    atomic_long_read(sk_memory_allocated(sk))>  sk_prot_mem(sk)[2])
>
> Why not sk_memory_allocated() returns the value ?
> Is it required to return pointer ?

Same thing. I don't feel strongly about this, and can change it.

>
>>   		return true;
>>   	return false;
>>   }
>> diff --git a/include/net/udp.h b/include/net/udp.h
>> index 67ea6fc..0e27388 100644
>> --- a/include/net/udp.h
>> +++ b/include/net/udp.h
>> @@ -105,7 +105,8 @@ static inline struct udp_hslot *udp_hashslot2(struct udp_table *table,
>>
>>   extern struct proto udp_prot;
>>
>> -extern atomic_long_t udp_memory_allocated;
>> +atomic_long_t *memory_allocated_udp(struct kmem_cgroup *sg);
>> +long *udp_sysctl_mem(struct kmem_cgroup *sg);
>>
>>   /* sysctl variables for udp */
>>   extern long sysctl_udp_mem[3];
>> diff --git a/include/trace/events/sock.h b/include/trace/events/sock.h
>> index 779abb9..12a6083 100644
>> --- a/include/trace/events/sock.h
>> +++ b/include/trace/events/sock.h
>> @@ -37,7 +37,7 @@ TRACE_EVENT(sock_exceed_buf_limit,
>>
>>   	TP_STRUCT__entry(
>>   		__array(char, name, 32)
>> -		__field(long *, sysctl_mem)
>> +		__field(long *, prot_mem)
>>   		__field(long, allocated)
>>   		__field(int, sysctl_rmem)
>>   		__field(int, rmem_alloc)
>> @@ -45,7 +45,7 @@ TRACE_EVENT(sock_exceed_buf_limit,
>>
>>   	TP_fast_assign(
>>   		strncpy(__entry->name, prot->name, 32);
>> -		__entry->sysctl_mem = prot->sysctl_mem;
>> +		__entry->prot_mem = sk->sk_prot->prot_mem(sk->sk_cgrp);
>>   		__entry->allocated = allocated;
>>   		__entry->sysctl_rmem = prot->sysctl_rmem[0];
>>   		__entry->rmem_alloc = atomic_read(&sk->sk_rmem_alloc);
>> @@ -54,9 +54,9 @@ TRACE_EVENT(sock_exceed_buf_limit,
>>   	TP_printk("proto:%s sysctl_mem=%ld,%ld,%ld allocated=%ld "
>>   		"sysctl_rmem=%d rmem_alloc=%d",
>>   		__entry->name,
>> -		__entry->sysctl_mem[0],
>> -		__entry->sysctl_mem[1],
>> -		__entry->sysctl_mem[2],
>> +		__entry->prot_mem[0],
>> +		__entry->prot_mem[1],
>> +		__entry->prot_mem[2],
>>   		__entry->allocated,
>>   		__entry->sysctl_rmem,
>>   		__entry->rmem_alloc)
>> diff --git a/init/Kconfig b/init/Kconfig
>> index d627783..5955ac2 100644
>> --- a/init/Kconfig
>> +++ b/init/Kconfig
>> @@ -690,6 +690,17 @@ config CGROUP_MEM_RES_CTLR_SWAP_ENABLED
>>   	  select this option (if, for some reason, they need to disable it
>>   	  then swapaccount=0 does the trick).
>>
>> +config CGROUP_KMEM
>> +	bool "Kernel Memory Resource Controller for Control Groups"
>> +	depends on CGROUPS
>> +	help
>> +	  The Kernel Memory cgroup can limit the amount of memory used by
>> +	  certain kernel objects in the system. Those are fundamentally
>> +	  different from the entities handled by the Memory Controller,
>> +	  which are page-based, and can be swapped. Users of the kmem
>> +	  cgroup can use it to guarantee that no group of processes will
>> +	  ever exhaust kernel resources alone.
>> +
>
> This help seems nice but please add Documentation/cgroup/kmem.
Yes, sure.

>
>
>
>
>>   config CGROUP_PERF
>>   	bool "Enable perf_event per-cpu per-container group (cgroup) monitoring"
>>   	depends on PERF_EVENTS&&  CGROUPS
>> diff --git a/mm/Makefile b/mm/Makefile
>> index 836e416..1b1aa24 100644
>> --- a/mm/Makefile
>> +++ b/mm/Makefile
>> @@ -45,6 +45,7 @@ obj-$(CONFIG_MIGRATION) += migrate.o
>>   obj-$(CONFIG_QUICKLIST) += quicklist.o
>>   obj-$(CONFIG_TRANSPARENT_HUGEPAGE) += huge_memory.o
>>   obj-$(CONFIG_CGROUP_MEM_RES_CTLR) += memcontrol.o page_cgroup.o
>> +obj-$(CONFIG_CGROUP_KMEM) += kmem_cgroup.o
>>   obj-$(CONFIG_MEMORY_FAILURE) += memory-failure.o
>>   obj-$(CONFIG_HWPOISON_INJECT) += hwpoison-inject.o
>>   obj-$(CONFIG_DEBUG_KMEMLEAK) += kmemleak.o
>> diff --git a/net/core/sock.c b/net/core/sock.c
>> index 3449df8..2d968ea 100644
>> --- a/net/core/sock.c
>> +++ b/net/core/sock.c
>> @@ -134,6 +134,24 @@
>>   #include<net/tcp.h>
>>   #endif
>>
>> +static DEFINE_RWLOCK(proto_list_lock);
>> +static LIST_HEAD(proto_list);
>> +
>> +int sockets_populate(struct cgroup_subsys *ss, struct cgroup *cgrp)
>> +{
>> +	struct proto *proto;
>> +	int ret = 0;
>> +
>> +	read_lock(&proto_list_lock);
>> +	list_for_each_entry(proto,&proto_list, node) {
>> +		if (proto->init_cgroup)
>> +			ret |= proto->init_cgroup(cgrp, ss);
>> +	}
>> +	read_unlock(&proto_list_lock);
>> +
>> +	return ret;
>> +}
>> +
>>   /*
>>    * Each address family might have different locking rules, so we have
>>    * one slock key per address family:
>> @@ -1114,6 +1132,31 @@ void sock_update_classid(struct sock *sk)
>>   EXPORT_SYMBOL(sock_update_classid);
>>   #endif
>>
>> +void sock_update_kmem_cgrp(struct sock *sk)
>> +{
>> +#ifdef CONFIG_CGROUP_KMEM
>> +	sk->sk_cgrp = kcg_from_task(current);
>> +
>> +	/*
>> +	 * We don't need to protect against anything task-related, because
>> +	 * we are basically stuck with the sock pointer that won't change,
>> +	 * even if the task that originated the socket changes cgroups.
>> +	 *
>> +	 * What we do have to guarantee, is that the chain leading us to
>> +	 * the top level won't change under our noses. Incrementing the
>> +	 * reference count via cgroup_exclude_rmdir guarantees that.
>> +	 */
>> +	cgroup_exclude_rmdir(&sk->sk_cgrp->css);
>> +#endif
>> +}
>
> I'm not sure this kind of bare cgroup code in core/sock.c will be
> welcomed by network guys.

What is your suggestion then? Just a wrapper or do you have something 
else in mind ?

>
>
>
>
>> +
>> +void sock_release_kmem_cgrp(struct sock *sk)
>> +{
>> +#ifdef CONFIG_CGROUP_KMEM
>> +	cgroup_release_and_wakeup_rmdir(&sk->sk_cgrp->css);
>> +#endif
>> +}
>> +
>>   /**
>>    *	sk_alloc - All socket objects are allocated here
>>    *	@net: the applicable net namespace
>> @@ -1139,6 +1182,7 @@ struct sock *sk_alloc(struct net *net, int family, gfp_t priority,
>>   		atomic_set(&sk->sk_wmem_alloc, 1);
>>
>>   		sock_update_classid(sk);
>> +		sock_update_kmem_cgrp(sk);
>>   	}
>>
>>   	return sk;
>> @@ -1170,6 +1214,7 @@ static void __sk_free(struct sock *sk)
>>   		put_cred(sk->sk_peer_cred);
>>   	put_pid(sk->sk_peer_pid);
>>   	put_net(sock_net(sk));
>> +	sock_release_kmem_cgrp(sk);
>>   	sk_prot_free(sk->sk_prot_creator, sk);
>>   }
>>
>> @@ -1287,8 +1332,8 @@ struct sock *sk_clone(const struct sock *sk, const gfp_t priority)
>>   		sk_set_socket(newsk, NULL);
>>   		newsk->sk_wq = NULL;
>>
>> -		if (newsk->sk_prot->sockets_allocated)
>> -			percpu_counter_inc(newsk->sk_prot->sockets_allocated);
>> +		if (sk_sockets_allocated(sk))
>> +			percpu_counter_inc(sk_sockets_allocated(sk));
> How about
> 	sk_sockets_allocated_inc(sk);
> ?
>
>
>>
>>   		if (sock_flag(newsk, SOCK_TIMESTAMP) ||
>>   		    sock_flag(newsk, SOCK_TIMESTAMPING_RX_SOFTWARE))
>> @@ -1676,29 +1721,51 @@ EXPORT_SYMBOL(sk_wait_data);
>>    */
>>   int __sk_mem_schedule(struct sock *sk, int size, int kind)
>>   {
>> -	struct proto *prot = sk->sk_prot;
>>   	int amt = sk_mem_pages(size);
>> +	struct proto *prot = sk->sk_prot;
>>   	long allocated;
>> +	int *memory_pressure;
>> +	long *prot_mem;
>> +	int parent_failure = 0;
>> +	struct kmem_cgroup *sg;
>>
>>   	sk->sk_forward_alloc += amt * SK_MEM_QUANTUM;
>> -	allocated = atomic_long_add_return(amt, prot->memory_allocated);
>> +
>> +	memory_pressure = sk_memory_pressure(sk);
>> +	prot_mem = sk_prot_mem(sk);
>> +
>> +	allocated = atomic_long_add_return(amt, sk_memory_allocated(sk));
>> +
>> +#ifdef CONFIG_CGROUP_KMEM
>> +	for (sg = sk->sk_cgrp->parent; sg != NULL; sg = sg->parent) {
>> +		long alloc;
>> +		/*
>> +		 * 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,
>> +					       sg_memory_allocated(prot, sg));
>> +		parent_failure |= (alloc>  sk_prot_mem(sk)[2]);
>> +	}
>> +#endif
>> +
>> +	/* Over hard limit (we, or our parents) */
>> +	if (parent_failure || (allocated>  prot_mem[2]))
>> +		goto suppress_allocation;
>>
>>   	/* Under limit. */
>> -	if (allocated<= prot->sysctl_mem[0]) {
>> -		if (prot->memory_pressure&&  *prot->memory_pressure)
>> -			*prot->memory_pressure = 0;
>> +	if (allocated<= prot_mem[0]) {
>> +		if (memory_pressure&&  *memory_pressure)
>> +			*memory_pressure = 0;
>>   		return 1;
>>   	}
>>
>>   	/* Under pressure. */
>> -	if (allocated>  prot->sysctl_mem[1])
>> +	if (allocated>  prot_mem[1])
>>   		if (prot->enter_memory_pressure)
>>   			prot->enter_memory_pressure(sk);
>>
>> -	/* Over hard limit. */
>> -	if (allocated>  prot->sysctl_mem[2])
>> -		goto suppress_allocation;
>> -
>>   	/* guarantee minimum buffer size under pressure */
>>   	if (kind == SK_MEM_RECV) {
>>   		if (atomic_read(&sk->sk_rmem_alloc)<  prot->sysctl_rmem[0])
>> @@ -1712,13 +1779,13 @@ int __sk_mem_schedule(struct sock *sk, int size, int kind)
>>   				return 1;
>>   	}
>>
>> -	if (prot->memory_pressure) {
>> +	if (memory_pressure) {
>>   		int alloc;
>>
>> -		if (!*prot->memory_pressure)
>> +		if (!*memory_pressure)
>>   			return 1;
>> -		alloc = percpu_counter_read_positive(prot->sockets_allocated);
>> -		if (prot->sysctl_mem[2]>  alloc *
>> +		alloc = percpu_counter_read_positive(sk_sockets_allocated(sk));
>> +		if (prot_mem[2]>  alloc *
>>   		    sk_mem_pages(sk->sk_wmem_queued +
>>   				 atomic_read(&sk->sk_rmem_alloc) +
>>   				 sk->sk_forward_alloc))
>> @@ -1741,7 +1808,13 @@ suppress_allocation:
>>
>>   	/* Alas. Undo changes. */
>>   	sk->sk_forward_alloc -= amt * SK_MEM_QUANTUM;
>> -	atomic_long_sub(amt, prot->memory_allocated);
>> +
>> +	atomic_long_sub(amt, sk_memory_allocated(sk));
>> +
>> +#ifdef CONFIG_CGROUP_KMEM
>> +	for (sg = sk->sk_cgrp->parent; sg != NULL; sg = sg->parent)
>> +		atomic_long_sub(amt, sg_memory_allocated(prot, sg));
>> +#endif
>>   	return 0;
>>   }
>>   EXPORT_SYMBOL(__sk_mem_schedule);
>> @@ -1753,14 +1826,24 @@ EXPORT_SYMBOL(__sk_mem_schedule);
>>   void __sk_mem_reclaim(struct sock *sk)
>>   {
>>   	struct proto *prot = sk->sk_prot;
>> +	struct kmem_cgroup *sg = sk->sk_cgrp;
>> +	int *memory_pressure = sk_memory_pressure(sk);
>>
>>   	atomic_long_sub(sk->sk_forward_alloc>>  SK_MEM_QUANTUM_SHIFT,
>> -		   prot->memory_allocated);
>> +		   sk_memory_allocated(sk));
>> +
>> +#ifdef CONFIG_CGROUP_KMEM
>> +	for (sg = sk->sk_cgrp->parent; sg != NULL; sg = sg->parent) {
>> +		atomic_long_sub(sk->sk_forward_alloc>>  SK_MEM_QUANTUM_SHIFT,
>> +						sg_memory_allocated(prot, sg));
>> +	}
>> +#endif
>> +
>>   	sk->sk_forward_alloc&= SK_MEM_QUANTUM - 1;
>>
>> -	if (prot->memory_pressure&&  *prot->memory_pressure&&
>> -	    (atomic_long_read(prot->memory_allocated)<  prot->sysctl_mem[0]))
>> -		*prot->memory_pressure = 0;
>> +	if (memory_pressure&&  *memory_pressure&&
>> +	    (atomic_long_read(sk_memory_allocated(sk))<  sk_prot_mem(sk)[0]))
>> +		*memory_pressure = 0;
>>   }
>>   EXPORT_SYMBOL(__sk_mem_reclaim);
>>
>
> IMHO, I like to hide atomic_long_xxxx ops under kmem cgroup ops.
>
> And use callbacks like
> 	kmem_cgroup_read(SOCKET_MEM_ALLOCATED, sk)
>
> If other component uses kmem_cgroup, a generic interface will be
> helpful because optimization/fix in generic interface will improve
> all users of kmem_cgroup.

I honestly don't like it too much.
It introduces at least one conditional to test for the kind of variable,
which can harm some fast paths, and the return value will not always be 
of the same type. Also, kmem_cgroup_read would not do too much besides 
acessing a data. Not a likely hot target for future optimizations.

>
>
>> @@ -2252,9 +2335,6 @@ void sk_common_release(struct sock *sk)
>>   }
>>   EXPORT_SYMBOL(sk_common_release);
>>
>> -static DEFINE_RWLOCK(proto_list_lock);
>> -static LIST_HEAD(proto_list);
>> -
>>   #ifdef CONFIG_PROC_FS
>>   #define PROTO_INUSE_NR	64	/* should be enough for the first time */
>>   struct prot_inuse {
>> @@ -2479,13 +2559,17 @@ static char proto_method_implemented(const void *method)
>>
>>   static void proto_seq_printf(struct seq_file *seq, struct proto *proto)
>>   {
>> +	struct kmem_cgroup *sg = kcg_from_task(current);
>> +
>>   	seq_printf(seq, "%-9s %4u %6d  %6ld   %-3s %6u   %-3s  %-10s "
>>   			"%2c %2c %2c %2c %2c %2c %2c %2c %2c %2c %2c %2c %2c %2c %2c %2c %2c %2c %2c\n",
>>   		   proto->name,
>>   		   proto->obj_size,
>>   		   sock_prot_inuse_get(seq_file_net(seq), proto),
>> -		   proto->memory_allocated != NULL ? atomic_long_read(proto->memory_allocated) : -1L,
>> -		   proto->memory_pressure != NULL ? *proto->memory_pressure ? "yes" : "no" : "NI",
>> +		   proto->memory_allocated != NULL ?
>> +			atomic_long_read(sg_memory_allocated(proto, sg)) : -1L,
>> +		   proto->memory_pressure != NULL ?
>> +			*sg_memory_pressure(proto, sg) ? "yes" : "no" : "NI",
>>   		   proto->max_header,
>>   		   proto->slab == NULL ? "no" : "yes",
>>   		   module_name(proto->owner),
>> diff --git a/net/decnet/af_decnet.c b/net/decnet/af_decnet.c
>> index 19acd00..463b299 100644
>> --- a/net/decnet/af_decnet.c
>> +++ b/net/decnet/af_decnet.c
>> @@ -458,13 +458,28 @@ static void dn_enter_memory_pressure(struct sock *sk)
>>   	}
>>   }
>>
>> +static atomic_long_t *memory_allocated_dn(struct kmem_cgroup *sg)
>> +{
>> +	return&decnet_memory_allocated;
>> +}
>> +
>> +static int *memory_pressure_dn(struct kmem_cgroup *sg)
>> +{
>> +	return&dn_memory_pressure;
>> +}
>> +
>> +static long *dn_sysctl_mem(struct kmem_cgroup *sg)
>> +{
>> +	return sysctl_decnet_mem;
>> +}
>> +
>>   static struct proto dn_proto = {
>>   	.name			= "NSP",
>>   	.owner			= THIS_MODULE,
>>   	.enter_memory_pressure	= dn_enter_memory_pressure,
>> -	.memory_pressure	=&dn_memory_pressure,
>> -	.memory_allocated	=&decnet_memory_allocated,
>> -	.sysctl_mem		= sysctl_decnet_mem,
>> +	.memory_pressure	= memory_pressure_dn,
>> +	.memory_allocated	= memory_allocated_dn,
>> +	.prot_mem		= dn_sysctl_mem,
>>   	.sysctl_wmem		= sysctl_decnet_wmem,
>>   	.sysctl_rmem		= sysctl_decnet_rmem,
>>   	.max_header		= DN_MAX_NSP_DATA_HEADER + 64,
>> diff --git a/net/ipv4/proc.c b/net/ipv4/proc.c
>> index b14ec7d..9c80acf 100644
>> --- a/net/ipv4/proc.c
>> +++ b/net/ipv4/proc.c
>> @@ -52,20 +52,22 @@ static int sockstat_seq_show(struct seq_file *seq, void *v)
>>   {
>>   	struct net *net = seq->private;
>>   	int orphans, sockets;
>> +	struct kmem_cgroup *sg = kcg_from_task(current);
>> +	struct percpu_counter *allocated = sg_sockets_allocated(&tcp_prot, sg);
>>
>>   	local_bh_disable();
>>   	orphans = percpu_counter_sum_positive(&tcp_orphan_count);
>> -	sockets = percpu_counter_sum_positive(&tcp_sockets_allocated);
>> +	sockets = percpu_counter_sum_positive(allocated);
>>   	local_bh_enable();
>>
>>   	socket_seq_show(seq);
>>   	seq_printf(seq, "TCP: inuse %d orphan %d tw %d alloc %d mem %ld\n",
>>   		   sock_prot_inuse_get(net,&tcp_prot), orphans,
>>   		   tcp_death_row.tw_count, sockets,
>> -		   atomic_long_read(&tcp_memory_allocated));
>> +		   atomic_long_read(sg_memory_allocated((&tcp_prot), sg)));
>>   	seq_printf(seq, "UDP: inuse %d mem %ld\n",
>>   		   sock_prot_inuse_get(net,&udp_prot),
>> -		   atomic_long_read(&udp_memory_allocated));
>> +		   atomic_long_read(sg_memory_allocated((&udp_prot), sg)));
>>   	seq_printf(seq, "UDPLITE: inuse %d\n",
>>   		   sock_prot_inuse_get(net,&udplite_prot));
>>   	seq_printf(seq, "RAW: inuse %d\n",
>> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
>> index 69fd720..5e89480 100644
>> --- a/net/ipv4/sysctl_net_ipv4.c
>> +++ b/net/ipv4/sysctl_net_ipv4.c
>> @@ -14,6 +14,8 @@
>>   #include<linux/init.h>
>>   #include<linux/slab.h>
>>   #include<linux/nsproxy.h>
>> +#include<linux/kmem_cgroup.h>
>> +#include<linux/swap.h>
>>   #include<net/snmp.h>
>>   #include<net/icmp.h>
>>   #include<net/ip.h>
>> @@ -174,6 +176,43 @@ static int proc_allowed_congestion_control(ctl_table *ctl,
>>   	return ret;
>>   }
>>
>> +static int ipv4_tcp_mem(ctl_table *ctl, int write,
>> +			   void __user *buffer, size_t *lenp,
>> +			   loff_t *ppos)
>> +{
>> +	int ret;
>> +	unsigned long vec[3];
>> +	struct kmem_cgroup *kmem = kcg_from_task(current);
>> +	struct net *net = current->nsproxy->net_ns;
>> +	int i;
>> +
>> +	ctl_table tmp = {
>> +		.data =&vec,
>> +		.maxlen = sizeof(vec),
>> +		.mode = ctl->mode,
>> +	};
>> +
>> +	if (!write) {
>> +		ctl->data =&net->ipv4.sysctl_tcp_mem;
>> +		return proc_doulongvec_minmax(ctl, write, buffer, lenp, ppos);
>> +	}
>> +
>> +	ret = proc_doulongvec_minmax(&tmp, write, buffer, lenp, ppos);
>> +	if (ret)
>> +		return ret;
>> +
>> +	for (i = 0; i<  3; i++)
>> +		if (vec[i]>  kmem->tcp_max_memory)
>> +			return -EINVAL;
>> +
>> +	for (i = 0; i<  3; i++) {
>> +		net->ipv4.sysctl_tcp_mem[i] = vec[i];
>> +		kmem->tcp_prot_mem[i] = net->ipv4.sysctl_tcp_mem[i];
>> +	}
>> +
>> +	return 0;
>> +}
>> +
>>   static struct ctl_table ipv4_table[] = {
>>   	{
>>   		.procname	= "tcp_timestamps",
>> @@ -433,13 +472,6 @@ static struct ctl_table ipv4_table[] = {
>>   		.proc_handler	= proc_dointvec
>>   	},
>>   	{
>> -		.procname	= "tcp_mem",
>> -		.data		=&sysctl_tcp_mem,
>> -		.maxlen		= sizeof(sysctl_tcp_mem),
>> -		.mode		= 0644,
>> -		.proc_handler	= proc_doulongvec_minmax
>> -	},
>> -	{
>>   		.procname	= "tcp_wmem",
>>   		.data		=&sysctl_tcp_wmem,
>>   		.maxlen		= sizeof(sysctl_tcp_wmem),
>> @@ -721,6 +753,12 @@ static struct ctl_table ipv4_net_table[] = {
>>   		.mode		= 0644,
>>   		.proc_handler	= ipv4_ping_group_range,
>>   	},
>> +	{
>> +		.procname	= "tcp_mem",
>> +		.maxlen		= sizeof(init_net.ipv4.sysctl_tcp_mem),
>> +		.mode		= 0644,
>> +		.proc_handler	= ipv4_tcp_mem,
>> +	},
>>   	{ }
>>   };
>>
>> @@ -734,6 +772,7 @@ EXPORT_SYMBOL_GPL(net_ipv4_ctl_path);
>>   static __net_init int ipv4_sysctl_init_net(struct net *net)
>>   {
>>   	struct ctl_table *table;
>> +	unsigned long limit;
>>
>>   	table = ipv4_net_table;
>>   	if (!net_eq(net,&init_net)) {
>> @@ -769,6 +808,12 @@ static __net_init int ipv4_sysctl_init_net(struct net *net)
>>
>>   	net->ipv4.sysctl_rt_cache_rebuild_count = 4;
>>
>> +	limit = nr_free_buffer_pages() / 8;
>> +	limit = max(limit, 128UL);
>> +	net->ipv4.sysctl_tcp_mem[0] = limit / 4 * 3;
>> +	net->ipv4.sysctl_tcp_mem[1] = limit;
>> +	net->ipv4.sysctl_tcp_mem[2] = net->ipv4.sysctl_tcp_mem[0] * 2;
>> +
>
> What this calculation means ? Documented somewhere ?
I just copied the numbers from the socket initialization, because I 
wanted to keep the same behaviour. No documentation there, no 
documentation here. I don't know if there is any particular reason to 
choose them over any other. If someone more knowleadgeable would
comment, I can use the chance to introduce a comment.

>
>
>
>>   	net->ipv4.ipv4_hdr = register_net_sysctl_table(net,
>>   			net_ipv4_ctl_path, table);
>>   	if (net->ipv4.ipv4_hdr == NULL)
>> diff --git a/net/ipv4/tcp.c b/net/ipv4/tcp.c
>> index 46febca..e1918fa 100644
>> --- a/net/ipv4/tcp.c
>> +++ b/net/ipv4/tcp.c
>> @@ -266,6 +266,7 @@
>>   #include<linux/crypto.h>
>>   #include<linux/time.h>
>>   #include<linux/slab.h>
>> +#include<linux/nsproxy.h>
>>
>>   #include<net/icmp.h>
>>   #include<net/tcp.h>
>> @@ -282,23 +283,12 @@ int sysctl_tcp_fin_timeout __read_mostly = TCP_FIN_TIMEOUT;
>>   struct percpu_counter tcp_orphan_count;
>>   EXPORT_SYMBOL_GPL(tcp_orphan_count);
>>
>> -long sysctl_tcp_mem[3] __read_mostly;
>>   int sysctl_tcp_wmem[3] __read_mostly;
>>   int sysctl_tcp_rmem[3] __read_mostly;
>>
>> -EXPORT_SYMBOL(sysctl_tcp_mem);
>>   EXPORT_SYMBOL(sysctl_tcp_rmem);
>>   EXPORT_SYMBOL(sysctl_tcp_wmem);
>>
>> -atomic_long_t tcp_memory_allocated;	/* Current allocated memory. */
>> -EXPORT_SYMBOL(tcp_memory_allocated);
>> -
>> -/*
>> - * Current number of TCP sockets.
>> - */
>> -struct percpu_counter tcp_sockets_allocated;
>> -EXPORT_SYMBOL(tcp_sockets_allocated);
>> -
>>   /*
>>    * TCP splice context
>>    */
>> @@ -308,23 +298,157 @@ struct tcp_splice_state {
>>   	unsigned int flags;
>>   };
>>
>> +#ifdef CONFIG_CGROUP_KMEM
>>   /*
>>    * Pressure flag: try to collapse.
>>    * Technical note: it is used by multiple contexts non atomically.
>>    * All the __sk_mem_schedule() is of this nature: accounting
>>    * is strict, actions are advisory and have some latency.
>>    */
>> -int tcp_memory_pressure __read_mostly;
>> -EXPORT_SYMBOL(tcp_memory_pressure);
>> -
>>   void tcp_enter_memory_pressure(struct sock *sk)
>>   {
>> +	struct kmem_cgroup *sg = sk->sk_cgrp;
>> +	if (!sg->tcp_memory_pressure) {
>> +		NET_INC_STATS(sock_net(sk), LINUX_MIB_TCPMEMORYPRESSURES);
>> +		sg->tcp_memory_pressure = 1;
>> +	}
>> +}
>> +
>> +long *tcp_sysctl_mem(struct kmem_cgroup *sg)
>> +{
>> +	return sg->tcp_prot_mem;
>> +}
>> +
>> +atomic_long_t *memory_allocated_tcp(struct kmem_cgroup *sg)
>> +{
>> +	return&(sg->tcp_memory_allocated);
>> +}
>> +
>> +static int tcp_write_maxmem(struct cgroup *cgrp, struct cftype *cft, u64 val)
>> +{
>> +	struct kmem_cgroup *sg = kcg_from_cgroup(cgrp);
>> +	struct net *net = current->nsproxy->net_ns;
>> +	int i;
>> +
>> +	if (!cgroup_lock_live_group(cgrp))
>> +		return -ENODEV;
>> +
>> +	/*
>> +	 * We can't allow more memory than our parents. Since this
>> +	 * will be tested for all calls, by induction, there is no need
>> +	 * to test any parent other than our own
>> +	 * */
>> +	if (sg->parent&&  (val>  sg->parent->tcp_max_memory))
>> +		val = sg->parent->tcp_max_memory;
>> +
>> +	sg->tcp_max_memory = val;
>> +
>> +	for (i = 0; i<  3; i++)
>> +		sg->tcp_prot_mem[i]  = min_t(long, val,
>> +					     net->ipv4.sysctl_tcp_mem[i]);
>> +
>> +	cgroup_unlock();
>> +
>> +	return 0;
>> +}
>> +
>
> Do we really need cgroup_lock/unlock ?
The task writing to a cgroup file not necessarily belongs to it. This 
means there is no guarantee that the cgroup will exist through the rest 
of this operation. Maybe this could be done with rcu, since all we need 
is a reference to the cgroup (and the parent). But other cgroup file 
writers seem to use this lock...
>
>
>
>> +static u64 tcp_read_maxmem(struct cgroup *cgrp, struct cftype *cft)
>> +{
>> +	struct kmem_cgroup *sg = kcg_from_cgroup(cgrp);
>> +	u64 ret;
>> +
>> +	if (!cgroup_lock_live_group(cgrp))
>> +		return -ENODEV;
>> +	ret = sg->tcp_max_memory;
>> +
>> +	cgroup_unlock();
>> +	return ret;
>> +}
>> +
>
>
> Hmm, can't you implement this function as
>
> 	kmem_cgroup_read(SOCK_TCP_MAXMEM, sg);

I can, but as I stated above, I don't think it is a nice change.

> Thanks,
> -Kame

Thank you very much for you attention.

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