From: Paolo Abeni <pabeni@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>,
Frederic Weisbecker <frederic@kernel.org>
Cc: Alex Belits <abelits@marvell.com>,
"rostedt@goodmis.org" <rostedt@goodmis.org>,
Prasun Kapoor <pkapoor@marvell.com>,
"mingo@kernel.org" <mingo@kernel.org>,
"davem@davemloft.net" <davem@davemloft.net>,
"linux-api@vger.kernel.org" <linux-api@vger.kernel.org>,
"peterz@infradead.org" <peterz@infradead.org>,
"linux-arch@vger.kernel.org" <linux-arch@vger.kernel.org>,
"catalin.marinas@arm.com" <catalin.marinas@arm.com>,
"tglx@linutronix.de" <tglx@linutronix.de>,
"will@kernel.org" <will@kernel.org>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
"netdev@vger.kernel.org" <netdev@vger.kernel.org>
Subject: Re: [PATCH v4 11/13] task_isolation: net: don't flush backlog on CPUs running isolated tasks
Date: Fri, 22 Jan 2021 17:13:44 +0100 [thread overview]
Message-ID: <4c9229e0e2d7ffabba1a8372d5335ddb28486b6e.camel@redhat.com> (raw)
In-Reply-To: <20210122141320.GA66969@fuller.cnet>
On Fri, 2021-01-22 at 11:13 -0300, Marcelo Tosatti wrote:
> On Thu, Oct 01, 2020 at 04:47:31PM +0200, Frederic Weisbecker wrote:
> > On Wed, Jul 22, 2020 at 02:58:24PM +0000, Alex Belits wrote:
> > > From: Yuri Norov <ynorov@marvell.com>
> > >
> > > so we don't need to flush it.
> >
> > What guarantees that we have no backlog on it?
>
> From Paolo's work to use lockless reading of
> per-CPU skb lists
>
> https://www.spinics.net/lists/netdev/msg682693.html
>
> It also exposed skb queue length to userspace
>
> https://www.spinics.net/lists/netdev/msg684939.html
>
> But if i remember correctly waiting for a RCU grace
> period was also necessary to ensure no backlog !?!
>
> Paolo would you please remind us what was the sequence of steps?
> (and then also, for the userspace isolation interface, where
> the application informs the kernel that its entering isolated
> mode, is just confirming the queues have zero length is
> sufficient?).
After commit 2de79ee27fdb52626ac4ac48ec6d8d52ba6f9047, for CONFIG_RPS
enabled build, with no RFS in place to ensure backlog will be empty on
CPU X, the user must:
- configure the RPS map on each device before the device goes up to
explicitly exclude CPU X.
If CPU X is isolated after some network device already went up, to
ensure that the backlog will be empty on CPU X the user must:
- configure RPS on all the network device to exclude CPU X (as in the
previous scenario)
- wait a RCU grace period
- wait untill the backlog len on CPU X reported by procfs is 0
Cheers,
Paolo
next prev parent reply other threads:[~2021-01-22 16:47 UTC|newest]
Thread overview: 49+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-22 14:44 [PATCH v4 00/13] "Task_isolation" mode Alex Belits
2020-07-22 14:47 ` [PATCH v4 01/13] task_isolation: vmstat: add quiet_vmstat_sync function Alex Belits
2020-07-22 14:48 ` [PATCH v4 02/13] task_isolation: vmstat: add vmstat_idle function Alex Belits
2020-07-22 14:49 ` [PATCH v4 03/13] task_isolation: userspace hard isolation from kernel Alex Belits
2020-10-01 13:56 ` Frederic Weisbecker
2020-10-04 14:44 ` [EXT] " Alex Belits
2020-10-04 23:14 ` Frederic Weisbecker
2020-10-05 18:52 ` Nitesh Narayan Lal
2020-10-06 10:35 ` Frederic Weisbecker
2020-10-17 1:13 ` Alex Belits
2020-10-17 1:08 ` Alex Belits
2020-10-17 16:08 ` Thomas Gleixner
2020-10-17 16:15 ` Alex Belits
2020-10-17 20:03 ` Thomas Gleixner
2020-10-06 11:01 ` Alex Belits
2020-10-01 14:40 ` Frederic Weisbecker
2020-10-04 15:01 ` [EXT] " Alex Belits
2020-07-22 14:51 ` [PATCH v4 04/13] task_isolation: Add task isolation hooks to arch-independent code Alex Belits
2020-07-22 14:51 ` [PATCH v4 05/13] task_isolation: Add xen-specific hook Alex Belits
2020-07-22 14:53 ` [PATCH 06/13] task_isolation: Add driver-specific hooks Alex Belits
2020-07-22 14:54 ` [PATCH v4 07/13] task_isolation: arch/x86: enable task isolation functionality Alex Belits
2020-07-22 14:55 ` [PATCH 08/13] task_isolation: arch/arm64: " Alex Belits
2020-07-22 14:56 ` [PATCH v4 09/13] task_isolation: arch/arm: " Alex Belits
2020-07-22 14:57 ` [PATCH v4 10/13] task_isolation: don't interrupt CPUs with tick_nohz_full_kick_cpu() Alex Belits
2020-10-01 14:44 ` Frederic Weisbecker
2020-10-04 15:22 ` [EXT] " Alex Belits
2020-10-06 21:41 ` Frederic Weisbecker
2020-10-17 0:17 ` Alex Belits
2020-07-22 14:58 ` [PATCH v4 11/13] task_isolation: net: don't flush backlog on CPUs running isolated tasks Alex Belits
2020-10-01 14:47 ` Frederic Weisbecker
2020-10-04 17:12 ` [EXT] " Alex Belits
2021-01-22 14:13 ` Marcelo Tosatti
2021-01-22 16:13 ` Paolo Abeni [this message]
2020-07-22 14:59 ` [PATCH v4 12/13] task_isolation: ringbuffer: don't interrupt CPUs running isolated tasks on buffer resize Alex Belits
2020-07-22 14:59 ` [PATCH 13/13] task_isolation: kick_all_cpus_sync: don't kick isolated cpus Alex Belits
2020-07-23 13:17 ` [PATCH v4 00/13] "Task_isolation" mode Thomas Gleixner
2020-07-23 14:26 ` Peter Zijlstra
2020-07-23 14:53 ` Thomas Gleixner
2020-07-23 14:29 ` Peter Zijlstra
2020-07-23 15:41 ` [EXT] " Alex Belits
2020-07-23 15:48 ` Peter Zijlstra
2020-07-23 16:19 ` Alex Belits
2020-07-23 15:18 ` Alex Belits
2020-07-23 15:49 ` Peter Zijlstra
2020-07-23 16:50 ` Alex Belits
2020-07-23 21:44 ` Thomas Gleixner
2020-07-24 3:00 ` [EXT] " Alex Belits
2020-07-24 16:08 ` Thomas Gleixner
2020-07-23 21:31 ` Thomas Gleixner
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