From: Jakub Kicinski <kuba@kernel.org>
To: Breno Leitao <leitao@debian.org>
Cc: davem@davemloft.net, pabeni@redhat.com, edumazet@google.com,
linux-kernel@vger.kernel.org, netdev@vger.kernel.org
Subject: Re: [PATCH net-next v2 4/4] net: dqs: make struct dql more cache efficient
Date: Tue, 9 Apr 2024 17:21:49 -0700 [thread overview]
Message-ID: <20240409172149.6f285b68@kernel.org> (raw)
In-Reply-To: <20240408172605.635508-5-leitao@debian.org>
On Mon, 8 Apr 2024 10:25:56 -0700 Breno Leitao wrote:
> With the previous change, struct dqs->stall_thrs will be in the hot path
> (at queue side), even if DQS is disabled.
>
> The other fields accessed in this function (last_obj_cnt and num_queued)
> are in the first cache line, let's move this field (stall_thrs) to the
> very first cache line, since there is a hole there.
>
> This does not change the structure size, since it moves an short (2
> bytes) to 4-bytes whole in the first cache line.
Doesn't this move the cache line bouncing problem to the other side?
Eric said "copy" I read that as "have two fields with the same value".
I think it's single digit number of alu instructions we'd be saving
here, not super convinced patch 3 is the right trade off...
next prev parent reply other threads:[~2024-04-10 0:21 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2024-04-08 17:25 [PATCH v2 0/4] net : dqs: optimize if stall threshold is not set Breno Leitao
2024-04-08 17:25 ` [PATCH net-next v2 1/4] net: dql: Avoid calling BUG() when WARN() is enough Breno Leitao
2024-04-08 17:25 ` [PATCH net-next v2 2/4] net: dql: Separate queue function responsibilities Breno Leitao
2024-04-08 17:25 ` [PATCH net-next v2 3/4] net: dql: Optimize stall information population Breno Leitao
2024-04-08 17:25 ` [PATCH net-next v2 4/4] net: dqs: make struct dql more cache efficient Breno Leitao
2024-04-10 0:21 ` Jakub Kicinski [this message]
2024-04-10 13:52 ` Breno Leitao
2024-04-11 1:45 ` Jakub Kicinski
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