From: Marcelo Tosatti <mtosatti@redhat.com>
To: 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 11:13:20 -0300 [thread overview]
Message-ID: <20210122141320.GA66969@fuller.cnet> (raw)
In-Reply-To: <20201001144731.GC6595@lothringen>
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?).
TIA!
>
> > Currently flush_all_backlogs()
> > enqueues corresponding work on all CPUs including ones that run
> > isolated tasks. It leads to breaking task isolation for nothing.
> >
> > In this patch, backlog flushing is enqueued only on non-isolated CPUs.
> >
> > Signed-off-by: Yuri Norov <ynorov@marvell.com>
> > [abelits@marvell.com: use safe task_isolation_on_cpu() implementation]
> > Signed-off-by: Alex Belits <abelits@marvell.com>
> > ---
> > net/core/dev.c | 7 ++++++-
> > 1 file changed, 6 insertions(+), 1 deletion(-)
> >
> > diff --git a/net/core/dev.c b/net/core/dev.c
> > index 90b59fc50dc9..83a282f7453d 100644
> > --- a/net/core/dev.c
> > +++ b/net/core/dev.c
> > @@ -74,6 +74,7 @@
> > #include <linux/cpu.h>
> > #include <linux/types.h>
> > #include <linux/kernel.h>
> > +#include <linux/isolation.h>
> > #include <linux/hash.h>
> > #include <linux/slab.h>
> > #include <linux/sched.h>
> > @@ -5624,9 +5625,13 @@ static void flush_all_backlogs(void)
> >
> > get_online_cpus();
> >
> > - for_each_online_cpu(cpu)
> > + smp_rmb();
>
> What is it ordering?
>
> > + for_each_online_cpu(cpu) {
> > + if (task_isolation_on_cpu(cpu))
> > + continue;
> > queue_work_on(cpu, system_highpri_wq,
> > per_cpu_ptr(&flush_works, cpu));
> > + }
> >
> > for_each_online_cpu(cpu)
> > flush_work(per_cpu_ptr(&flush_works, cpu));
>
> Thanks.
next prev parent reply other threads:[~2021-01-22 15:04 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 [this message]
2021-01-22 16:13 ` Paolo Abeni
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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