From: Marcelo Tosatti <mtosatti@redhat.com>
To: Nitesh Narayan Lal <nitesh@redhat.com>
Cc: linux-kernel@vger.kernel.org, netdev@vger.kernel.org,
linux-pci@vger.kernel.org, frederic@kernel.org,
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
Subject: Re: [RFC][Patch v1 2/3] i40e: limit msix vectors based on housekeeping CPUs
Date: Fri, 11 Sep 2020 12:23:44 -0300 [thread overview]
Message-ID: <20200911152344.GA21157@fuller.cnet> (raw)
In-Reply-To: <20200909150818.313699-3-nitesh@redhat.com>
On Wed, Sep 09, 2020 at 11:08:17AM -0400, 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>
> ---
> drivers/net/ethernet/intel/i40e/i40e_main.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/net/ethernet/intel/i40e/i40e_main.c b/drivers/net/ethernet/intel/i40e/i40e_main.c
> index 2e433fdbf2c3..3b4cd4b3de85 100644
> --- a/drivers/net/ethernet/intel/i40e/i40e_main.c
> +++ b/drivers/net/ethernet/intel/i40e/i40e_main.c
> @@ -5,6 +5,7 @@
> #include <linux/of_net.h>
> #include <linux/pci.h>
> #include <linux/bpf.h>
> +#include <linux/sched/isolation.h>
> #include <generated/utsrelease.h>
>
> /* Local includes */
> @@ -11002,7 +11003,7 @@ static int i40e_init_msix(struct i40e_pf *pf)
> * will use any remaining vectors to reach as close as we can to the
> * number of online CPUs.
> */
> - cpus = num_online_cpus();
> + cpus = num_housekeeping_cpus();
> pf->num_lan_msix = min_t(int, cpus, vectors_left / 2);
> vectors_left -= pf->num_lan_msix;
>
> --
> 2.27.0
For patches 1 and 2:
Reviewed-by: Marcelo Tosatti <mtosatti@redhat.com>
next prev parent reply other threads:[~2020-09-11 16:25 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 [this message]
2020-09-17 18:23 ` Jesse Brandeburg
2020-09-17 18:31 ` Nitesh Narayan Lal
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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