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Re: [PATCH] netfilter: nf_conntrack: use safer way to lock all buckets

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Sasha Levin <sasha.levin@oracle.com> wrote:
> When we need to lock all buckets in the connection hashtable we'd attempt to
> lock 1024 spinlocks, which is way more preemption levels than supported by
> the kernel.

You're right.

> Fix this by using a global lock and synchronize all buckets on it when we
> need to lock them all. This is pretty heavyweight, but is only done when we
> need to resize the hashtable, and that doesn't happen often enough (or at all).

> diff --git a/net/netfilter/nf_conntrack_core.c b/net/netfilter/nf_conntrack_core.c
> index 3cb3cb8..3c008ce 100644
> --- a/net/netfilter/nf_conntrack_core.c
> +++ b/net/netfilter/nf_conntrack_core.c
> @@ -66,6 +66,32 @@ EXPORT_SYMBOL_GPL(nf_conntrack_locks);
>  __cacheline_aligned_in_smp DEFINE_SPINLOCK(nf_conntrack_expect_lock);
>  EXPORT_SYMBOL_GPL(nf_conntrack_expect_lock);
>  
> +spinlock_t nf_conntrack_locks_all_lock;
> +bool nf_conntrack_locks_all;

Seems both of these can be static and __read_mostly too --
as you already note resizing virtually never happens.

Otherwise:
Reviewed-by: Florian Westphal <fw@strlen.de>

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[PATCH] netfilter: nf_conntrack: use safer way to lock all buckets Sasha Levin <sasha.levin@oracle.com> - 2016-01-05 03:30 +0100
  RE: [PATCH] netfilter: nf_conntrack: use safer way to lock all  buckets David Laight <David.Laight@ACULAB.COM> - 2016-01-05 12:20 +0100
  Re: [PATCH] netfilter: nf_conntrack: use safer way to lock all  buckets Florian Westphal <fw@strlen.de> - 2016-01-10 02:10 +0100
    Re: [PATCH] netfilter: nf_conntrack: use safer way to lock all  buckets Pablo Neira Ayuso <pablo@netfilter.org> - 2016-01-13 18:00 +0100
      Re: [PATCH] netfilter: nf_conntrack: use safer way to lock all  buckets Sasha Levin <sasha.levin@oracle.com> - 2016-01-13 19:40 +0100
  Re: [PATCH] netfilter: nf_conntrack: use safer way to lock all  buckets Jesper Dangaard Brouer <brouer@redhat.com> - 2016-01-14 15:20 +0100

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