From: Florian Westphal <fw@strlen.de>
To: Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz>
Cc: pablo@netfilter.org, kadlec@netfilter.org, fw@strlen.de,
netfilter-devel@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH 1/3] Revert "netfilter: x_tables: Update remaining dereference to RCU"
Date: Thu, 4 Mar 2021 08:43:37 +0100 [thread overview]
Message-ID: <20210304074337.GH17911@breakpoint.cc> (raw)
In-Reply-To: <20210304013116.8420-2-mark.tomlinson@alliedtelesis.co.nz>
Mark Tomlinson <mark.tomlinson@alliedtelesis.co.nz> wrote:
> This reverts commit 443d6e86f821a165fae3fc3fc13086d27ac140b1.
>
> This (and the following) patch basically re-implemented the RCU
> mechanisms of patch 784544739a25. That patch was replaced because of the
> performance problems that it created when replacing tables. Now, we have
> the same issue: the call to synchronize_rcu() makes replacing tables
> slower by as much as an order of magnitude.
>
> See https://lore.kernel.org/patchwork/patch/151796/ for why using RCU is
> not a good idea.
Please don't add links for the rationale.
next prev parent reply other threads:[~2021-03-04 7:45 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-03-04 1:31 [PATCH 0/3] Don't use RCU for x_tables synchronization Mark Tomlinson
2021-03-04 1:31 ` [PATCH 1/3] Revert "netfilter: x_tables: Update remaining dereference to RCU" Mark Tomlinson
2021-03-04 7:43 ` Florian Westphal [this message]
2021-03-04 1:31 ` [PATCH 2/3] Revert "netfilter: x_tables: Switch synchronization " Mark Tomlinson
2021-03-04 7:44 ` Florian Westphal
2021-03-04 1:31 ` [PATCH 3/3] netfilter: x_tables: Use correct memory barriers Mark Tomlinson
2021-03-04 7:46 ` Florian Westphal
2021-03-05 3:30 ` Mark Tomlinson
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