From: Pablo Neira Ayuso <pablo@netfilter.org>
To: Florian Westphal <fw@strlen.de>
Cc: netfilter-devel@vger.kernel.org
Subject: Re: [PATCH v4 nf-next 0/2] netfilter: x_tables: speed up iptables-restore
Date: Tue, 24 Oct 2017 18:04:17 +0200 [thread overview]
Message-ID: <20171024160417.GA12134@salvia> (raw)
In-Reply-To: <20171011231351.8517-1-fw@strlen.de>
On Thu, Oct 12, 2017 at 01:13:49AM +0200, Florian Westphal wrote:
> iptables-restore can take quite a long time when sytem is busy, in order
> of half a minute or more.
>
> The main reason for this is the way ip(6)tables performs table swap:
>
> When xt_replace_table assigns the new ruleset pointer, it does
> not wait for other processors to finish with old ruleset.
>
> Instead it relies on the counter sequence lock in get_counters().
>
> This works but this is costly if system is busy as each counter read
> operation can possibly be restarted indefinitely.
>
> Instead, make xt_replace_table wait until all processors are known to not
> use the old ruleset anymore.
>
> This allows to read the old counters without any locking, no cpu is
> using the ruleset anymore so counters can't change either.
Series applied, thanks.
prev parent reply other threads:[~2017-10-24 16:04 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-10-11 23:13 [PATCH v4 nf-next 0/2] netfilter: x_tables: speed up iptables-restore Florian Westphal
2017-10-11 23:13 ` [PATCH nf-next v4 1/2] netfilter: x_tables: make xt_replace_table wait until old rules are not used anymore Florian Westphal
2017-10-11 23:13 ` [PATCH nf-next v4 2/2] netfilter: x_tables: don't use seqlock when fetching old counters Florian Westphal
2017-10-24 16:04 ` Pablo Neira Ayuso [this message]
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