Re: [PATCH v2 1/9] per-netns ipv4 sysctl_tcp_mem

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On Wed,  7 Sep 2011 01:23:11 -0300
Glauber Costa <glommer@xxxxxxxxxxxxx> wrote:

> This patch allows each namespace to independently set up
> its levels for tcp memory pressure thresholds. This patch
> alone does not buy much: we need to make this values
> per group of process somehow. This is achieved in the
> patches that follows in this patchset.
> 
> 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>


Hmm, it may be better to post this patch as independent one.

I'm not familiar with this area...but try review ;)

> ---
>  include/net/netns/ipv4.h   |    1 +
>  include/net/tcp.h          |    1 -
>  net/ipv4/sysctl_net_ipv4.c |   51 +++++++++++++++++++++++++++++++++++++------
>  net/ipv4/tcp.c             |   13 +++-------
>  4 files changed, 49 insertions(+), 17 deletions(-)
> 
> 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;

Hmm, in original placement, sysctl_tcp_mem[] was on __read_mostly
area. Doesn't this placement cause many cache invalidations ?



> diff --git a/include/net/tcp.h b/include/net/tcp.h
> index 149a415..6bfdd9b 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;
> diff --git a/net/ipv4/sysctl_net_ipv4.c b/net/ipv4/sysctl_net_ipv4.c
> index 69fd720..0d74b9d 100644
> --- a/net/ipv4/sysctl_net_ipv4.c
> +++ b/net/ipv4/sysctl_net_ipv4.c
> @@ -14,6 +14,7 @@
>  #include <linux/init.h>
>  #include <linux/slab.h>
>  #include <linux/nsproxy.h>
> +#include <linux/swap.h>
>  #include <net/snmp.h>
>  #include <net/icmp.h>
>  #include <net/ip.h>
> @@ -174,6 +175,36 @@ 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 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++)
> +		net->ipv4.sysctl_tcp_mem[i] = vec[i];
> +
> +	return 0;
> +}
> +
>  static struct ctl_table ipv4_table[] = {
>  	{
>  		.procname	= "tcp_timestamps",
> @@ -433,13 +464,6 @@ 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 +745,12 @@ 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 +764,7 @@ 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 +800,12 @@ 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;
> +
>  	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..f06df24 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>
> @@ -282,11 +283,9 @@ 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);
>  
> @@ -3277,14 +3276,10 @@ void __init tcp_init(void)
>  	sysctl_tcp_max_orphans = cnt / 2;
>  	sysctl_max_syn_backlog = max(128, cnt / 256);
>  
> -	limit = nr_free_buffer_pages() / 8;
> -	limit = max(limit, 128UL);
> -	sysctl_tcp_mem[0] = limit / 4 * 3;
> -	sysctl_tcp_mem[1] = limit;
> -	sysctl_tcp_mem[2] = sysctl_tcp_mem[0] * 2;
> -
>  	/* Set per-socket limits to no more than 1/128 the pressure threshold */
> -	limit = ((unsigned long)sysctl_tcp_mem[1]) << (PAGE_SHIFT - 7);
> +	limit = (unsigned long)init_net.ipv4.sysctl_tcp_mem[1];
> +	limit <<= (PAGE_SHIFT - 7);
> +

I'm not sure but...why defined as 'long'  ?



BTW, when I grep,

tcp_input.c:        atomic_long_read(&tcp_memory_allocated) < sysctl_tcp_mem[0])
tcp_input.c:    if (atomic_long_read(&tcp_memory_allocated) >= sysctl_tcp_mem[0])

Don't you need to change this ?



Thanks,
-Kame







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