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From: Nitesh Narayan Lal <nitesh@redhat.com>
To: Marcelo Tosatti <mtosatti@redhat.com>
Cc: Thomas Gleixner <tglx@linutronix.de>,
	Robin Murphy <robin.murphy@arm.com>,
	linux-kernel@vger.kernel.org, linux-api@vger.kernel.org,
	frederic@kernel.org, juri.lelli@redhat.com, abelits@marvell.com,
	bhelgaas@google.com, linux-pci@vger.kernel.org,
	rostedt@goodmis.org, mingo@kernel.org, peterz@infradead.org,
	davem@davemloft.net, akpm@linux-foundation.org,
	sfr@canb.auug.org.au, stephen@networkplumber.org,
	rppt@linux.vnet.ibm.com, jinyuqi@huawei.com,
	zhangshaokun@hisilicon.com
Subject: Re: [Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs
Date: Thu, 4 Feb 2021 14:17:16 -0500	[thread overview]
Message-ID: <d8884413-84b4-b204-85c5-810342807d21@redhat.com> (raw)
In-Reply-To: <20210204190647.GA32868@fuller.cnet>


On 2/4/21 2:06 PM, Marcelo Tosatti wrote:
> On Thu, Feb 04, 2021 at 01:47:38PM -0500, Nitesh Narayan Lal wrote:

[...]

>>>>> Nitesh, is there anything preventing this from being fixed
>>>>> in userspace ? (as Thomas suggested previously).
>>>> Everything with is not managed can be steered by user space.
>>> Yes, but it seems to be racy (that is, there is a window where the 
>>> interrupt can be delivered to an isolated CPU).
>>>
>>> ethtool ->
>>> xgbe_set_channels ->
>>> xgbe_full_restart_dev ->
>>> xgbe_alloc_memory ->
>>> xgbe_alloc_channels ->
>>> cpumask_local_spread
>>>
>>> Also ifconfig eth0 down / ifconfig eth0 up leads
>>> to cpumask_spread_local.
>> There's always that possibility.
> Then there is a window where isolation can be broken.
>
>> We have to ensure that we move the IRQs by a tuned daemon or some other
>> userspace script every time there is a net-dev change (eg. device comes up,
>> creates VFs, etc).
> Again, race window open can result in interrupt to isolated CPU.


Yes, and if I am not mistaken then that always has been a problem with
these userspace solutions.

>
>>> How about adding a new flag for isolcpus instead?
>>>
>> Do you mean a flag based on which we can switch the affinity mask to
>> housekeeping for all the devices at the time of IRQ distribution?
> Yes a new flag for isolcpus. HK_FLAG_IRQ_SPREAD or some better name.
>
>

Does sounds like a nice idea to explore, lets see what Thomas thinks about it.

-- 
Thanks
Nitesh


  reply	other threads:[~2021-02-04 19:19 UTC|newest]

Thread overview: 48+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2020-06-25 22:34 [PATCH v4 0/3] Preventing job distribution to isolated CPUs Nitesh Narayan Lal
2020-06-25 22:34 ` [Patch v4 1/3] lib: Restrict cpumask_local_spread to houskeeping CPUs Nitesh Narayan Lal
2020-06-29 16:11   ` Nitesh Narayan Lal
2020-07-01  0:32     ` Andrew Morton
2020-07-01  0:47       ` Nitesh Narayan Lal
2021-01-27 11:57   ` Robin Murphy
2021-01-27 12:19     ` Marcelo Tosatti
2021-01-27 12:36       ` Robin Murphy
2021-01-27 13:09         ` Marcelo Tosatti
2021-01-27 13:49           ` Robin Murphy
2021-01-27 14:16           ` Nitesh Narayan Lal
2021-01-28 15:56           ` Thomas Gleixner
2021-01-28 16:33             ` Marcelo Tosatti
     [not found]             ` <02ac9d85-7ddd-96da-1252-4663feea7c9f@marvell.com>
2021-02-01 17:50               ` [EXT] " Marcelo Tosatti
2021-01-28 16:02       ` Thomas Gleixner
2021-01-28 16:59         ` Marcelo Tosatti
2021-01-28 17:35           ` Nitesh Narayan Lal
2021-01-28 20:01           ` Thomas Gleixner
     [not found]             ` <d2a4dc97-a9ed-e0e7-3b9c-c56ae46f6608@redhat.com>
     [not found]               ` <20210129142356.GB40876@fuller.cnet>
2021-01-29 17:34                 ` [EXT] " Alex Belits
     [not found]                 ` <18584612-868c-0f88-5de2-dc93c8638816@redhat.com>
2021-02-05 19:56                   ` Thomas Gleixner
2021-02-04 18:15             ` Marcelo Tosatti
2021-02-04 18:47               ` Nitesh Narayan Lal
2021-02-04 19:06                 ` Marcelo Tosatti
2021-02-04 19:17                   ` Nitesh Narayan Lal [this message]
2021-02-05 22:23                     ` Thomas Gleixner
2021-02-05 22:26                       ` Thomas Gleixner
2021-02-07  0:43                       ` Nitesh Narayan Lal
2021-02-11 15:55                         ` Nitesh Narayan Lal
2021-03-04 18:15                           ` Nitesh Narayan Lal
     [not found]                             ` <faa8d84e-db67-7fbe-891e-f4987f106b20@marvell.com>
2021-03-04 23:23                               ` [EXT] " Nitesh Narayan Lal
2021-04-06 17:22                             ` Jesse Brandeburg
2021-04-07 15:18                               ` Nitesh Narayan Lal
2021-04-08 18:49                                 ` Nitesh Narayan Lal
2021-04-14 16:11                                 ` Jesse Brandeburg
2021-04-15 22:11                                   ` Nitesh Narayan Lal
2021-04-29 21:44                                     ` Nitesh Lal
2021-04-30  1:48                                       ` Jesse Brandeburg
2021-04-30 13:10                                         ` Nitesh Lal
2021-04-30  7:10                                       ` Thomas Gleixner
2021-04-30 16:14                                         ` Nitesh Lal
2021-04-30 18:21                                           ` Thomas Gleixner
2021-04-30 21:07                                             ` Nitesh Lal
2021-05-01  2:21                                               ` Jesse Brandeburg
2021-05-03 13:15                                                 ` Nitesh Lal
2020-06-25 22:34 ` [Patch v4 2/3] PCI: Restrict probe functions to housekeeping CPUs Nitesh Narayan Lal
2020-06-25 22:34 ` [Patch v4 3/3] net: Restrict receive packets queuing " Nitesh Narayan Lal
2020-06-26 11:14   ` Peter Zijlstra
2020-06-26 17:20     ` David Miller

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