netdev - Re: /proc/net/sockstat invalid memory accounting or memory leak in latest kernels? (trying to debug)

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Date:	Sun, 16 Nov 2014 10:11:35 -0800
From:	Eric Dumazet <eric.dumazet@...il.com>
To:	Denys Fedoryshchenko <nuclearcat@...learcat.com>
Cc:	Neal Cardwell <ncardwell@...gle.com>,
	Yuchung Cheng <ycheng@...gle.com>, netdev@...r.kernel.org
Subject: Re: /proc/net/sockstat invalid memory accounting or memory leak in
 latest kernels? (trying to debug)

On Sun, 2014-11-16 at 10:54 +0200, Denys Fedoryshchenko wrote:
> As latest findings, when servers are going crazy because of tcp memory 
> invalid accounting.
> First of all i upgraded kernel to latest version 3.17.3 and added also 
> patch from upcoming kernel,
> "12) Don't call sock_kfree_s() with NULL pointers, this function also 
> has the side effect of adjusting
> the socket memory usage.  From Cong Wang.", but it didnt helped.
> 
> I added printk_ratelimited to places where suspicious values might 
> appear, and got some more information.
> First, is not very suspicious, no idea if it is a problem:
> [ 1413.031622] sk ffff8817184d8680 sk_mem_charge negative -10752 by 4352
> [ 1413.032027] sk ffff8817184d8680 sk_mem_charge negative -15104 by 4352
> [ 1415.768465] sk ffff881666842d80 sk_mem_charge negative -9984 by 4352
> [ 1415.768868] sk ffff881666842d80 sk_mem_charge negative -14336 by 4352
> [ 1415.769268] sk ffff881666842d80 sk_mem_charge negative -18688 by 4352
> [ 1415.769681] sk ffff881666842d80 sk_mem_charge negative -9088 by 4352
> [ 1418.933799] sk ffff8816dd640000 sk_mem_charge negative -9984 by 4352
> [ 1418.934205] sk ffff8816dd640000 sk_mem_charge negative -14336 by 4352
> [ 1418.934604] sk ffff8816dd640000 sk_mem_charge negative -18688 by 4352
> [ 1427.131310] sk ffff881731801a00 sk_mem_charge negative -11776 by 4352
> [ 1428.564640] sk ffff881731801a00 sk_mem_charge negative -11008 by 4352
> [ 1429.134279] sk ffff881731801a00 sk_mem_charge negative -11776 by 4352
> [ 1429.134691] sk ffff881731801a00 sk_mem_charge negative -16128 by 4352
> [ 1430.666541] sk ffff881731801a00 sk_mem_charge negative -10496 by 4352
> [ 1431.395099] sk ffff881731801a00 sk_mem_charge negative -12032 by 4352
> [ 1431.395506] sk ffff881731801a00 sk_mem_charge negative -16384 by 4352
> [ 1431.877862] sk ffff881731801a00 sk_mem_charge negative -11648 by 4352
> Second is always linked with crashes, it is sk_mem_uncharge and 
> sk_forward_alloc goes negative. Patch to show message
> for sk_mem_uncharge in sock.h is very simple:
> 
>   static inline void sk_mem_uncharge(struct sock *sk, int size)
> @@ -1480,6 +1485,8 @@
>          if (!sk_has_account(sk))
>                  return;
>          sk->sk_forward_alloc += size;
> +       if (sk->sk_forward_alloc < -8192)
> +           printk_ratelimited(KERN_WARNING"sk %p sk_mem_uncharge 
> negative %d by %d\n", sk, sk->sk_forward_alloc, size);
>   }
> 


Could you describe your hardware setup and networking setup ?



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