From: Nitesh Narayan Lal <nitesh@redhat.com>
To: Jesse Brandeburg <jesse.brandeburg@intel.com>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
linux-pci@vger.kernel.org, frederic@kernel.org,
mtosatti@redhat.com, sassmann@redhat.com,
jeffrey.t.kirsher@intel.com, jacob.e.keller@intel.com,
jlelli@redhat.com, hch@infradead.org, bhelgaas@google.com,
mike.marciniszyn@intel.com, dennis.dalessandro@intel.com,
thomas.lendacky@amd.com, jerinj@marvell.com,
mathias.nyman@intel.com, jiri@nvidia.com,
"Luis Claudio R. Goncalves" <lgoncalv@redhat.com>
Subject: Re: [RFC][Patch v1 2/3] i40e: limit msix vectors based on housekeeping CPUs
Date: Thu, 17 Sep 2020 14:31:07 -0400 [thread overview]
Message-ID: <9a73ab21-1ad6-9a08-b7e7-53ef85649563@redhat.com> (raw)
In-Reply-To: <20200917112359.00006e10@intel.com>
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On 9/17/20 2:23 PM, Jesse Brandeburg wrote:
> Nitesh Narayan Lal wrote:
>
>> In a realtime environment, it is essential to isolate unwanted IRQs from
>> isolated CPUs to prevent latency overheads. Creating MSIX vectors only
>> based on the online CPUs could lead to a potential issue on an RT setup
>> that has several isolated CPUs but a very few housekeeping CPUs. This is
>> because in these kinds of setups an attempt to move the IRQs to the
>> limited housekeeping CPUs from isolated CPUs might fail due to the per
>> CPU vector limit. This could eventually result in latency spikes because
>> of the IRQ threads that we fail to move from isolated CPUs.
>>
>> This patch prevents i40e to add vectors only based on available
>> housekeeping CPUs by using num_housekeeping_cpus().
>>
>> Signed-off-by: Nitesh Narayan Lal <nitesh@redhat.com>
> The driver changes are straightforward, but this isn't the only driver
> with this issue, right?
Indeed, I was hoping to modify them over the time with some testing.
> I'm sure ixgbe and ice both have this problem
> too, you should fix them as well, at a minimum, and probably other
> vendors drivers:
Sure, I can atleast include ixgbe and ice in the next posting if that makes
sense.
The reason I skipped them is that I was not very sure about the right way to
test these changes.
>
> $ rg -c --stats num_online_cpus drivers/net/ethernet
> ...
> 50 files contained matches
>
> for this patch i40e
> Acked-by: Jesse Brandeburg <jesse.brandeburg@intel.com>
>
--
Thanks
Nitesh
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next prev parent reply other threads:[~2020-09-17 18:32 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-09-09 15:08 [RFC] [PATCH v1 0/3] isolation: limit msix vectors based on housekeeping CPUs Nitesh Narayan Lal
2020-09-09 15:08 ` [RFC][Patch v1 1/3] sched/isolation: API to get num of hosekeeping CPUs Nitesh Narayan Lal
2020-09-17 18:18 ` Jesse Brandeburg
2020-09-17 18:43 ` Nitesh Narayan Lal
2020-09-17 20:11 ` Bjorn Helgaas
2020-09-17 21:48 ` Jacob Keller
2020-09-17 22:09 ` Nitesh Narayan Lal
2020-09-21 23:40 ` Frederic Weisbecker
2020-09-22 3:16 ` Nitesh Narayan Lal
2020-09-22 10:08 ` Frederic Weisbecker
2020-09-22 13:50 ` Nitesh Narayan Lal
2020-09-22 20:58 ` Frederic Weisbecker
2020-09-22 21:15 ` Nitesh Narayan Lal
2020-09-22 21:26 ` Andrew Lunn
2020-09-22 22:20 ` Nitesh Narayan Lal
2020-09-09 15:08 ` [RFC][Patch v1 2/3] i40e: limit msix vectors based on housekeeping CPUs Nitesh Narayan Lal
2020-09-11 15:23 ` Marcelo Tosatti
2020-09-17 18:23 ` Jesse Brandeburg
2020-09-17 18:31 ` Nitesh Narayan Lal [this message]
2020-09-21 22:58 ` Frederic Weisbecker
2020-09-22 3:08 ` Nitesh Narayan Lal
2020-09-22 9:54 ` Frederic Weisbecker
2020-09-22 13:34 ` Nitesh Narayan Lal
2020-09-22 20:44 ` Frederic Weisbecker
2020-09-22 21:05 ` Nitesh Narayan Lal
2020-09-09 15:08 ` [RFC][Patch v1 3/3] PCI: Limit pci_alloc_irq_vectors as per " Nitesh Narayan Lal
2020-09-10 19:22 ` Marcelo Tosatti
2020-09-10 19:31 ` Nitesh Narayan Lal
2020-09-22 13:54 ` Nitesh Narayan Lal
2020-09-22 21:08 ` Frederic Weisbecker
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