From: Herbert Xu <herbert@gondor.apana.org.au>
To: Arend Van Spriel <arend.vanspriel@broadcom.com>
Cc: "Toke Høiland-Jørgensen" <toke@redhat.com>,
"Felix Fietkau" <nbd@nbd.name>,
linux-wireless@vger.kernel.org, johannes@sipsolutions.net
Subject: Re: [PATCH 5/5] mac80211: set NETIF_F_LLTX when using intermediate tx queues
Date: Tue, 16 Apr 2019 15:44:44 +0800 [thread overview]
Message-ID: <20190416074444.pdubbh6fbibdnhi7@gondor.apana.org.au> (raw)
In-Reply-To: <773e4dff-29fd-22b4-e4bc-cd5a94c66dc2@broadcom.com>
On Sun, Apr 14, 2019 at 11:44:17AM +0200, Arend Van Spriel wrote:
> + Herbert
>
> On 3/16/2019 7:14 PM, Toke Høiland-Jørgensen wrote:
> > Felix Fietkau <nbd@nbd.name> writes:
> >
> > > When using iTXQ, tx sequence number allocation and statistics are run at
> > > dequeue time. Because of that, it is safe to enable NETIF_F_LLTX, which
> > > allows tx handlers to run on multiple CPUs in parallel.
> >
> > Cool, didn't know about that flag.
>
> It is water under the bridge as this patch got applied already, but I
> stumbled upon it just recently and didn't know about that flag either. So I
> looked for more information about it and found the definition [1], but the
> comment seemed important enough to send this reply.
>
> NETIF_F_LLTX_BIT, /* LockLess TX - deprecated. Please */
> /* do not use LLTX in new drivers */
The most obvious problem with LLTX is that it can cause AF_PACKET
to see packets twice. But the more subtle issue is that with a
proper design this lock should have no contention anyway.
So please explain why you want to use this in your driver and where
the contention is coming from?
Cheers,
--
Email: Herbert Xu <herbert@gondor.apana.org.au>
Home Page: http://gondor.apana.org.au/~herbert/
PGP Key: http://gondor.apana.org.au/~herbert/pubkey.txt
next prev parent reply other threads:[~2019-04-16 7:44 UTC|newest]
Thread overview: 43+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-03-16 17:06 [PATCH 1/5] mac80211: mesh: drop redundant rcu_read_lock/unlock calls Felix Fietkau
2019-03-16 17:06 ` [PATCH 2/5] mac80211: fix memory accounting with A-MSDU aggregation Felix Fietkau
2019-03-16 18:12 ` Toke Høiland-Jørgensen
2019-03-16 17:06 ` [PATCH 3/5] mac80211: calculate hash for fq without holding fq->lock in itxq enqueue Felix Fietkau
2019-03-16 18:13 ` Toke Høiland-Jørgensen
2019-03-16 17:06 ` [PATCH 4/5] mac80211: run late dequeue late tx handlers without holding fq->lock Felix Fietkau
2019-03-16 18:13 ` Toke Høiland-Jørgensen
2022-12-05 9:46 ` Wen Gong
2022-12-07 6:30 ` Wen Gong
2022-12-12 8:31 ` Wen Gong
2019-03-16 17:06 ` [PATCH 5/5] mac80211: set NETIF_F_LLTX when using intermediate tx queues Felix Fietkau
2019-03-16 18:14 ` Toke Høiland-Jørgensen
2019-04-14 9:44 ` Arend Van Spriel
2019-04-14 11:19 ` Felix Fietkau
2019-04-14 12:34 ` Arend Van Spriel
2019-04-16 7:34 ` Arend Van Spriel
2019-04-16 7:44 ` Herbert Xu [this message]
2019-04-16 8:04 ` Arend Van Spriel
2019-04-16 8:36 ` Herbert Xu
2019-04-16 8:37 ` Johannes Berg
2019-04-16 9:17 ` Arend Van Spriel
2019-04-16 9:29 ` Herbert Xu
2019-04-16 9:33 ` Toke Høiland-Jørgensen
2019-04-16 9:33 ` Johannes Berg
2019-04-16 9:37 ` Herbert Xu
2019-04-16 9:39 ` Johannes Berg
2019-04-16 10:02 ` Toke Høiland-Jørgensen
2019-04-17 2:11 ` Herbert Xu
2019-04-17 8:28 ` Toke Høiland-Jørgensen
2019-04-16 13:13 ` Herbert Xu
2019-04-16 13:18 ` Toke Høiland-Jørgensen
2019-04-17 3:38 ` Herbert Xu
2019-04-17 9:09 ` Toke Høiland-Jørgensen
2019-04-17 9:16 ` Arend Van Spriel
2019-04-17 9:17 ` Toke Høiland-Jørgensen
2019-04-23 12:41 ` Johannes Berg
2019-04-25 8:35 ` Herbert Xu
2019-04-25 8:39 ` Johannes Berg
2019-04-25 8:44 ` Herbert Xu
2019-04-25 8:49 ` Johannes Berg
2019-04-16 19:13 ` Johannes Berg
2019-04-17 2:13 ` Herbert Xu
2019-04-16 9:38 ` Toke Høiland-Jørgensen
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