From: Jakub Kicinski <kuba@kernel.org>
To: Herbert Xu <herbert@gondor.apana.org.au>
Cc: davem@davemloft.net, netdev@vger.kernel.org, edumazet@google.com,
pabeni@redhat.com, alexander.duyck@gmail.com,
hkallweit1@gmail.com, andrew@lunn.ch, willemb@google.com,
michael.chan@broadcom.com, jesse.brandeburg@intel.com,
anthony.l.nguyen@intel.com
Subject: Re: [PATCH net-next v3 7/7] net: piggy back on the memory barrier in bql when waking queues
Date: Wed, 12 Apr 2023 06:54:08 -0700 [thread overview]
Message-ID: <20230412065408.59e02bb7@kernel.org> (raw)
In-Reply-To: <ZDZKaoPaiy6Itj7P@gondor.apana.org.au>
On Wed, 12 Apr 2023 14:06:34 +0800 Herbert Xu wrote:
> On Thu, Apr 06, 2023 at 05:41:40PM -0700, Jakub Kicinski wrote:
> > I wanted to keep the same semantics as netdev_tx_completed_queue()
> > which only barriers if (bytes). Not in the least to make it obvious
> > to someone looking at the code of netdev_txq_completed_mb() (and not
> > the comment above it) that it doesn't _always_ put a barrier in.
>
> OK, but I think we should instead change netdev_tx_compelted_queue
> to do the smp_mb unconditionally. We should never optimise for the
> unlikely case, and it is extremely unlikely for a TX cleanup routine
> to wind up with nothing to do.
I don't understand what you're trying to argue. The whole point of
the patch is to use the BQL barrier and BQL returns early, before
the barrier.
I don't think many people actually build kernels with BQL=n so the other
branch is more *documentation* than it is relevant, executed code.
next prev parent reply other threads:[~2023-04-12 13:54 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-04-05 22:31 [PATCH net-next v3 0/7] net: lockless stop/wake combo macros Jakub Kicinski
2023-04-05 22:31 ` [PATCH net-next v3 1/7] docs: net: reformat driver.rst from a list to sections Jakub Kicinski
2023-04-05 22:31 ` [PATCH net-next v3 2/7] docs: net: move the probe and open/close sections of driver.rst up Jakub Kicinski
2023-04-05 22:31 ` [PATCH net-next v3 3/7] docs: net: use C syntax highlight in driver.rst Jakub Kicinski
2023-04-05 22:31 ` [PATCH net-next v3 4/7] net: provide macros for commonly copied lockless queue stop/wake code Jakub Kicinski
2023-04-06 7:22 ` Herbert Xu
2023-04-05 22:31 ` [PATCH net-next v3 5/7] ixgbe: use new queue try_stop/try_wake macros Jakub Kicinski
2023-04-05 22:31 ` [PATCH net-next v3 6/7] bnxt: " Jakub Kicinski
2023-04-05 22:31 ` [PATCH net-next v3 7/7] net: piggy back on the memory barrier in bql when waking queues Jakub Kicinski
2023-04-06 7:35 ` Herbert Xu
2023-04-07 0:41 ` Jakub Kicinski
2023-04-12 6:06 ` Herbert Xu
2023-04-12 13:54 ` Jakub Kicinski [this message]
2023-04-13 2:31 ` Herbert Xu
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