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From: "Björn Töpel" <bjorn.topel@intel.com>
To: "Jesper Dangaard Brouer" <brouer@redhat.com>,
	"Björn Töpel" <bjorn.topel@gmail.com>
Cc: ast@kernel.org, daniel@iogearbox.net, netdev@vger.kernel.org,
	bpf@vger.kernel.org, magnus.karlsson@intel.com,
	davem@davemloft.net, kuba@kernel.org, hawk@kernel.org,
	john.fastabend@gmail.com, intel-wired-lan@lists.osuosl.org
Subject: Re: [PATCH bpf-next 3/6] xsk: introduce xsk_do_redirect_rx_full() helper
Date: Fri, 4 Sep 2020 17:39:17 +0200	[thread overview]
Message-ID: <dfa75afc-ceb7-76ce-6ba3-3b89c53f92f3@intel.com> (raw)
In-Reply-To: <20200904171143.5868999a@carbon>

On 2020-09-04 17:11, Jesper Dangaard Brouer wrote:
> On Fri,  4 Sep 2020 15:53:28 +0200 Björn Töpel
> <bjorn.topel@gmail.com> wrote:
> 
>> From: Björn Töpel <bjorn.topel@intel.com>
>> 
>> The xsk_do_redirect_rx_full() helper can be used to check if a
>> failure of xdp_do_redirect() was due to the AF_XDP socket had a
>> full Rx ring.
> 
> This is very AF_XDP specific.  I think that the cpumap could likely 
> benefit from similar approach? e.g. if the cpumap kthread is
> scheduled on the same CPU.
> 

At least I thought this was *very* AF_XDP specific, since the kernel is
dependent of that userland runs. Allocation (source) and Rx ring (sink).
Maybe I was wrong! :-)

The thing with AF_XDP zero-copy, is that we sort of assume that if a
user enabled that most packets will have XDP_REDIRECT to an AF_XDP socket.


> But for cpumap we only want this behavior if sched on the same CPU
> as RX-NAPI.  This could be "seen" by the cpumap code itself in the
> case bq_flush_to_queue() drops packets, check if rcpu->cpu equal 
> smp_processor_id().  Maybe I'm taking this too far?
> 

Interesting. So, if you're running on the same core, and redirect fail
for CPUMAP, you'd like to yield the NAPI loop? Is that really OK from a
fairness perspective? I mean, with AF_XDP zero-copy we pretty much know
that all actions will be redirect to socket. For CPUMAP type of
applications, can that assumption be made?


Björn


WARNING: multiple messages have this Message-ID (diff)
From: =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?= <bjorn.topel@intel.com>
To: intel-wired-lan@osuosl.org
Subject: [Intel-wired-lan] [PATCH bpf-next 3/6] xsk: introduce xsk_do_redirect_rx_full() helper
Date: Fri, 4 Sep 2020 17:39:17 +0200	[thread overview]
Message-ID: <dfa75afc-ceb7-76ce-6ba3-3b89c53f92f3@intel.com> (raw)
In-Reply-To: <20200904171143.5868999a@carbon>

On 2020-09-04 17:11, Jesper Dangaard Brouer wrote:
> On Fri,  4 Sep 2020 15:53:28 +0200 Bj?rn T?pel
> <bjorn.topel@gmail.com> wrote:
> 
>> From: Bj?rn T?pel <bjorn.topel@intel.com>
>> 
>> The xsk_do_redirect_rx_full() helper can be used to check if a
>> failure of xdp_do_redirect() was due to the AF_XDP socket had a
>> full Rx ring.
> 
> This is very AF_XDP specific.  I think that the cpumap could likely 
> benefit from similar approach? e.g. if the cpumap kthread is
> scheduled on the same CPU.
> 

At least I thought this was *very* AF_XDP specific, since the kernel is
dependent of that userland runs. Allocation (source) and Rx ring (sink).
Maybe I was wrong! :-)

The thing with AF_XDP zero-copy, is that we sort of assume that if a
user enabled that most packets will have XDP_REDIRECT to an AF_XDP socket.


> But for cpumap we only want this behavior if sched on the same CPU
> as RX-NAPI.  This could be "seen" by the cpumap code itself in the
> case bq_flush_to_queue() drops packets, check if rcpu->cpu equal 
> smp_processor_id().  Maybe I'm taking this too far?
> 

Interesting. So, if you're running on the same core, and redirect fail
for CPUMAP, you'd like to yield the NAPI loop? Is that really OK from a
fairness perspective? I mean, with AF_XDP zero-copy we pretty much know
that all actions will be redirect to socket. For CPUMAP type of
applications, can that assumption be made?


Bj?rn


  reply	other threads:[~2020-09-04 15:39 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-09-04 13:53 [PATCH bpf-next 0/6] xsk: exit NAPI loop when AF_XDP Rx ring is full Björn Töpel
2020-09-04 13:53 ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-04 13:53 ` [PATCH bpf-next 1/6] xsk: improve xdp_do_redirect() error codes Björn Töpel
2020-09-04 13:53   ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-04 13:53 ` [PATCH bpf-next 2/6] xdp: introduce xdp_do_redirect_ext() function Björn Töpel
2020-09-04 13:53   ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-04 13:53 ` [PATCH bpf-next 3/6] xsk: introduce xsk_do_redirect_rx_full() helper Björn Töpel
2020-09-04 13:53   ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-04 15:11   ` Jesper Dangaard Brouer
2020-09-04 15:11     ` [Intel-wired-lan] " Jesper Dangaard Brouer
2020-09-04 15:39     ` Björn Töpel [this message]
2020-09-04 15:39       ` =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-07 12:45       ` Jesper Dangaard Brouer
2020-09-07 12:45         ` [Intel-wired-lan] " Jesper Dangaard Brouer
2020-09-04 13:53 ` [PATCH bpf-next 4/6] i40e, xsk: finish napi loop if AF_XDP Rx queue is full Björn Töpel
2020-09-04 13:53   ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-04 13:53 ` [PATCH bpf-next 5/6] ice, " Björn Töpel
2020-09-04 13:53   ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-04 13:53 ` [PATCH bpf-next 6/6] ixgbe, " Björn Töpel
2020-09-04 13:53   ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-04 15:35   ` Jesper Dangaard Brouer
2020-09-04 15:35     ` [Intel-wired-lan] " Jesper Dangaard Brouer
2020-09-04 15:54     ` Björn Töpel
2020-09-04 15:54       ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-04 13:59 ` [PATCH bpf-next 0/6] xsk: exit NAPI loop when AF_XDP Rx ring " Björn Töpel
2020-09-04 13:59   ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-08 10:32   ` Maxim Mikityanskiy
2020-09-08 10:32     ` [Intel-wired-lan] " Maxim Mikityanskiy
2020-09-08 11:37     ` Magnus Karlsson
2020-09-08 11:37       ` [Intel-wired-lan] " Magnus Karlsson
2020-09-08 12:21       ` Björn Töpel
2020-09-08 12:21         ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-09 15:37     ` Jesper Dangaard Brouer
2020-09-09 15:37       ` [Intel-wired-lan] " Jesper Dangaard Brouer
2020-09-04 14:27 ` Jesper Dangaard Brouer
2020-09-04 14:27   ` [Intel-wired-lan] " Jesper Dangaard Brouer
2020-09-04 14:32   ` Björn Töpel
2020-09-04 14:32     ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-04 23:58     ` Jakub Kicinski
2020-09-04 23:58       ` [Intel-wired-lan] " Jakub Kicinski
2020-09-07 13:37       ` Björn Töpel
2020-09-07 13:37         ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-07 18:40         ` Jakub Kicinski
2020-09-07 18:40           ` [Intel-wired-lan] " Jakub Kicinski
2020-09-08  6:58           ` Björn Töpel
2020-09-08  6:58             ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-08 17:24             ` Jakub Kicinski
2020-09-08 17:24               ` [Intel-wired-lan] " Jakub Kicinski
2020-09-08 18:28               ` Björn Töpel
2020-09-08 18:28                 ` [Intel-wired-lan] " =?unknown-8bit?q?Bj=C3=B6rn_T=C3=B6pel?=
2020-09-08 18:34                 ` Jakub Kicinski
2020-09-08 18:34                   ` [Intel-wired-lan] " Jakub Kicinski

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