[PATCH] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

[PATCH] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

[Eric Dumazet]

From: Eric Dumazet <edumazet@google.com>

order-5 allocations can fail with current kernels, we should
try to reduce allocation sizes to allow network namespace
creation.

Reported-by: Julien Tinnes <jln@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_metrics.c |   13 ++++++++-----
 1 file changed, 8 insertions(+), 5 deletions(-)

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 53bc584..15e93c4 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -1030,14 +1030,17 @@ static int __net_init tcp_net_metrics_init(struct net *net)
 		else
 			slots = 8 * 1024;
 	}
-
+retry:
 	net->ipv4.tcp_metrics_hash_log = order_base_2(slots);
 	size = sizeof(struct tcpm_hash_bucket) << net->ipv4.tcp_metrics_hash_log;
 
-	net->ipv4.tcp_metrics_hash = kzalloc(size, GFP_KERNEL);
-	if (!net->ipv4.tcp_metrics_hash)
-		return -ENOMEM;
-
+	net->ipv4.tcp_metrics_hash = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
+	if (!net->ipv4.tcp_metrics_hash) {
+		if (slots <= 16)
+			return -ENOMEM;
+		slots >>= 1;
+		goto retry;
+	}
 	return 0;
 }
 

Re: [PATCH] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

[Joe Perches]

On Thu, 2012-11-15 at 15:41 -0800, Eric Dumazet wrote:
> From: Eric Dumazet <edumazet@google.com>
> 
> order-5 allocations can fail with current kernels, we should
> try to reduce allocation sizes to allow network namespace
> creation.
> 
> Reported-by: Julien Tinnes <jln@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>
> ---
>  net/ipv4/tcp_metrics.c |   13 ++++++++-----
>  1 file changed, 8 insertions(+), 5 deletions(-)
> 
> diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
> index 53bc584..15e93c4 100644
> --- a/net/ipv4/tcp_metrics.c
> +++ b/net/ipv4/tcp_metrics.c
> @@ -1030,14 +1030,17 @@ static int __net_init tcp_net_metrics_init(struct net *net)
>  		else
>  			slots = 8 * 1024;
>  	}
> -
> +retry:
>  	net->ipv4.tcp_metrics_hash_log = order_base_2(slots);
>  	size = sizeof(struct tcpm_hash_bucket) << net->ipv4.tcp_metrics_hash_log;
>  
> -	net->ipv4.tcp_metrics_hash = kzalloc(size, GFP_KERNEL);
> -	if (!net->ipv4.tcp_metrics_hash)
> -		return -ENOMEM;
> -
> +	net->ipv4.tcp_metrics_hash = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
> +	if (!net->ipv4.tcp_metrics_hash) {
> +		if (slots <= 16)
> +			return -ENOMEM;

maybe readd the warning for OOM reporting here?

Re: [PATCH] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

[Eric Dumazet]

On Thu, 2012-11-15 at 15:55 -0800, Joe Perches wrote:

> maybe readd the warning for OOM reporting here?
> 


Storing tcp metrics is a best effort, this can be silently ignored.

And order-0 are going to work, unless machine is in critical state,
that gives enough room.

Re: [PATCH] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Thu, 15 Nov 2012 15:41:04 -0800

> From: Eric Dumazet <edumazet@google.com>
> 
> order-5 allocations can fail with current kernels, we should
> try to reduce allocation sizes to allow network namespace
> creation.
> 
> Reported-by: Julien Tinnes <jln@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

Indeed, this has to be done better.

But this kind of retry solution results in non-deterministic behavior.
Yes the tcp metrics cache is best effort, but it's size can influence
behavior in a substantial way depending upon the workload.

I would suggest that we instead use different limits, ones which the
page allocator will satisfy for us always with GFP_KERNEL.

1) include linux/mmzone.h

2) Make the two limits based upon PAGE_ALLOC_COSTLY_ORDER.

That is, make the larger table size PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER
and the smaller one PAGE_SIZE << (PAGE_ALLOC_COSTLY_ORDER - 1).

How about something like this?

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 53bc584..d4b2d42 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -1,7 +1,6 @@
 #include <linux/rcupdate.h>
 #include <linux/spinlock.h>
 #include <linux/jiffies.h>
-#include <linux/bootmem.h>
 #include <linux/module.h>
 #include <linux/cache.h>
 #include <linux/slab.h>
@@ -9,6 +8,7 @@
 #include <linux/tcp.h>
 #include <linux/hash.h>
 #include <linux/tcp_metrics.h>
+#include <linux/mmzone.h>
 
 #include <net/inet_connection_sock.h>
 #include <net/net_namespace.h>
@@ -1025,10 +1025,12 @@ static int __net_init tcp_net_metrics_init(struct net *net)
 
 	slots = tcpmhash_entries;
 	if (!slots) {
-		if (totalram_pages >= 128 * 1024)
-			slots = 16 * 1024;
-		else
-			slots = 8 * 1024;
+		int order = PAGE_ALLOC_COSTLY_ORDER;
+
+		if (totalram_pages < 128 * 1024)
+			order--;
+		slots = (PAGE_SIZE << order) /
+			sizeof(struct tcpm_hash_bucket);
 	}
 
 	net->ipv4.tcp_metrics_hash_log = order_base_2(slots);

Re: [PATCH] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

[Eric Dumazet]

On Fri, 2012-11-16 at 01:39 -0500, David Miller wrote:
> From: Eric Dumazet <eric.dumazet@gmail.com>
> Date: Thu, 15 Nov 2012 15:41:04 -0800
> 
> > From: Eric Dumazet <edumazet@google.com>
> > 
> > order-5 allocations can fail with current kernels, we should
> > try to reduce allocation sizes to allow network namespace
> > creation.
> > 
> > Reported-by: Julien Tinnes <jln@google.com>
> > Signed-off-by: Eric Dumazet <edumazet@google.com>
> 
> Indeed, this has to be done better.
> 
> But this kind of retry solution results in non-deterministic behavior.
> Yes the tcp metrics cache is best effort, but it's size can influence
> behavior in a substantial way depending upon the workload.
> 
> I would suggest that we instead use different limits, ones which the
> page allocator will satisfy for us always with GFP_KERNEL.
> 
> 1) include linux/mmzone.h
> 
> 2) Make the two limits based upon PAGE_ALLOC_COSTLY_ORDER.
> 
> That is, make the larger table size PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER
> and the smaller one PAGE_SIZE << (PAGE_ALLOC_COSTLY_ORDER - 1).

Well, we dont really know what the size needs to be, and your proposal
reduces the size by a 4 factor, even for the initial namespace.

Julien report was about Chrome browser own netns, on a suspend/resume
cycle (or something like that)

If size can influence behavior, we could try a vmalloc() if kmalloc()
fails...

Thanks

[PATCH v3] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

order-5 allocations can fail with current kernels, we should
try vmalloc() as well.

Reported-by: Julien Tinnes <jln@google.com>
Signed-off-by: Eric Dumazet <edumazet@google.com>
---
 net/ipv4/tcp_metrics.c |   12 +++++++++---
 1 file changed, 9 insertions(+), 3 deletions(-)

diff --git a/net/ipv4/tcp_metrics.c b/net/ipv4/tcp_metrics.c
index 53bc584..f696d7c 100644
--- a/net/ipv4/tcp_metrics.c
+++ b/net/ipv4/tcp_metrics.c
@@ -1,7 +1,6 @@
 #include <linux/rcupdate.h>
 #include <linux/spinlock.h>
 #include <linux/jiffies.h>
-#include <linux/bootmem.h>
 #include <linux/module.h>
 #include <linux/cache.h>
 #include <linux/slab.h>
@@ -9,6 +8,7 @@
 #include <linux/tcp.h>
 #include <linux/hash.h>
 #include <linux/tcp_metrics.h>
+#include <linux/vmalloc.h>
 
 #include <net/inet_connection_sock.h>
 #include <net/net_namespace.h>
@@ -1034,7 +1034,10 @@ static int __net_init tcp_net_metrics_init(struct net *net)
 	net->ipv4.tcp_metrics_hash_log = order_base_2(slots);
 	size = sizeof(struct tcpm_hash_bucket) << net->ipv4.tcp_metrics_hash_log;
 
-	net->ipv4.tcp_metrics_hash = kzalloc(size, GFP_KERNEL);
+	net->ipv4.tcp_metrics_hash = kzalloc(size, GFP_KERNEL | __GFP_NOWARN);
+	if (!net->ipv4.tcp_metrics_hash)
+		net->ipv4.tcp_metrics_hash = vzalloc(size);
+
 	if (!net->ipv4.tcp_metrics_hash)
 		return -ENOMEM;
 
@@ -1055,7 +1058,10 @@ static void __net_exit tcp_net_metrics_exit(struct net *net)
 			tm = next;
 		}
 	}
-	kfree(net->ipv4.tcp_metrics_hash);
+	if (is_vmalloc_addr(net->ipv4.tcp_metrics_hash))
+		vfree(net->ipv4.tcp_metrics_hash);
+	else
+		kfree(net->ipv4.tcp_metrics_hash);
 }
 
 static __net_initdata struct pernet_operations tcp_net_metrics_ops = {

Re: [PATCH] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

[David Miller]

From: Eric Dumazet <eric.dumazet@gmail.com>
Date: Fri, 16 Nov 2012 07:31:53 -0800

> Well, we dont really know what the size needs to be, and your proposal
> reduces the size by a 4 factor, even for the initial namespace.
> 
> Julien report was about Chrome browser own netns, on a suspend/resume
> cycle (or something like that)
> 
> If size can influence behavior, we could try a vmalloc() if kmalloc()
> fails...

Agreed.

> [PATCH v3] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures
> 
> order-5 allocations can fail with current kernels, we should
> try vmalloc() as well.
> 
> Reported-by: Julien Tinnes <jln@google.com>
> Signed-off-by: Eric Dumazet <edumazet@google.com>

This looks great, applied, thanks.

Re: [PATCH] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

[Julien Tinnes]

On Fri, Nov 16, 2012 at 7:31 AM, Eric Dumazet <eric.dumazet@gmail.com> wrote:
> On Fri, 2012-11-16 at 01:39 -0500, David Miller wrote:
>> From: Eric Dumazet <eric.dumazet@gmail.com>
>> Date: Thu, 15 Nov 2012 15:41:04 -0800
>>
>> > From: Eric Dumazet <edumazet@google.com>
>> >
>> > order-5 allocations can fail with current kernels, we should
>> > try to reduce allocation sizes to allow network namespace
>> > creation.
>> >
>> > Reported-by: Julien Tinnes <jln@google.com>
>> > Signed-off-by: Eric Dumazet <edumazet@google.com>
>>
>> Indeed, this has to be done better.
>>
>> But this kind of retry solution results in non-deterministic behavior.
>> Yes the tcp metrics cache is best effort, but it's size can influence
>> behavior in a substantial way depending upon the workload.
>>
>> I would suggest that we instead use different limits, ones which the
>> page allocator will satisfy for us always with GFP_KERNEL.
>>
>> 1) include linux/mmzone.h
>>
>> 2) Make the two limits based upon PAGE_ALLOC_COSTLY_ORDER.
>>
>> That is, make the larger table size PAGE_SIZE << PAGE_ALLOC_COSTLY_ORDER
>> and the smaller one PAGE_SIZE << (PAGE_ALLOC_COSTLY_ORDER - 1).
>
> Well, we dont really know what the size needs to be, and your proposal
> reduces the size by a 4 factor, even for the initial namespace.
>
> Julien report was about Chrome browser own netns, on a suspend/resume
> cycle (or something like that)

It happens when users start Chrome. Chrome will create one new network
NS (for the sandbox).

This has been used for a few years now, but we had our first report in
January of this year and we've been getting a few reports very
recently at a rate that is starting to worry me (crbug.com/110756).

Thanks a lot for helping with this!

Julien

Re: [PATCH] tcp: handle tcp_net_metrics_init() order-5 memory allocation failures

[Eric Dumazet]

On Fri, 2012-11-16 at 10:51 -0800, Julien Tinnes wrote:

> It happens when users start Chrome. Chrome will create one new network
> NS (for the sandbox).
> 
> This has been used for a few years now, but we had our first report in
> January of this year and we've been getting a few reports very
> recently at a rate that is starting to worry me (crbug.com/110756).
> 
> Thanks a lot for helping with this!

Thanks for bringing this issue to our attention !