From: Jakub Kicinski <kuba@kernel.org>
To: Kris Pan <kris.pan@intel.com>
Cc: edumazet@google.com, davem@davemloft.net, pabeni@redhat.com,
horms@kernel.org, atomasov@redhat.com, oliver.sang@intel.com,
netdev@vger.kernel.org, linux-kernel@vger.kernel.org
Subject: Re: [PATCH v2] net: iterate online nodes in skb_defer_free_flush()
Date: Tue, 15 Sep 2026 16:40:08 -0700 [thread overview]
Message-ID: <20260915164008.4f65ddc4@kernel.org> (raw)
In-Reply-To: <20260911023804.3503989-1-kris.pan@intel.com>
On Fri, 11 Sep 2026 10:38:04 +0800 Kris Pan wrote:
> skb_attempt_defer_free() only queues skbs on the current CPU's node
> (numa_node_id() of a running CPU), which is always online, so the
> flush loop never needs to visit nodes that are merely possible.
>
> for_each_node() walks node_possible_map. On machines where the
> possible map is much larger than the online map -- e.g. a POWER10
> LPAR with 32 possible but 1 online node -- the flush loop touches 31
> cold, always-empty per-node lists on every softirq pass, showing up
> as skb_defer_free_flush() and _find_next_bit() overhead.
>
> Use for_each_online_node() to iterate only node_online_map.
>
> Loopback UDP throughput in a QEMU guest with 32 possible / 1 online
> nodes (bench_udp, 8 senders, 6 interleaved runs) improves by ~5%.
Clashiko confirms this is racy:
https://netdev-ai.bots.linux.dev/sashiko/#/patchset/20260911023804.3503989-1-kris.pan@intel.com
--
pw-bot: cr
next prev parent reply other threads:[~2026-09-15 23:40 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2026-09-11 2:04 [PATCH] " Kris Pan
2026-09-11 2:38 ` [PATCH v2] " Kris Pan
2026-09-15 23:40 ` Jakub Kicinski [this message]
2026-09-15 23:53 ` Kris Pan
2026-09-16 0:00 ` Eric Dumazet
2026-09-11 2:39 ` [PATCH] " Eric Dumazet
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