netdev - Re: [PATCH mlx5-next] RDMA/mlx5: Don't use cached IRQ affinity mask

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Date:   Tue, 17 Jul 2018 11:58:31 +0300
From:   Leon Romanovsky <leon@...nel.org>
To:     Max Gurtovoy <maxg@...lanox.com>
Cc:     Steve Wise <swise@...ngridcomputing.com>,
        Sagi Grimberg <sagi@...mberg.me>,
        Doug Ledford <dledford@...hat.com>,
        Jason Gunthorpe <jgg@...lanox.com>,
        RDMA mailing list <linux-rdma@...r.kernel.org>,
        Saeed Mahameed <saeedm@...lanox.com>,
        linux-netdev <netdev@...r.kernel.org>
Subject: Re: [PATCH mlx5-next] RDMA/mlx5: Don't use cached IRQ affinity mask

On Tue, Jul 17, 2018 at 11:46:40AM +0300, Max Gurtovoy wrote:
>
>
> On 7/16/2018 8:08 PM, Steve Wise wrote:
> > Hey Max:
> >
> >
>
> Hey,
>
> > On 7/16/2018 11:46 AM, Max Gurtovoy wrote:
> > >
> > >
> > > On 7/16/2018 5:59 PM, Sagi Grimberg wrote:
> > > >
> > > > > Hi,
> > > > > I've tested this patch and seems problematic at this moment.
> > > >
> > > > Problematic how? what are you seeing?
> > >
> > > Connection failures and same error Steve saw:
> > >
> > > [Mon Jul 16 16:19:11 2018] nvme nvme0: Connect command failed, error
> > > wo/DNR bit: -16402
> > > [Mon Jul 16 16:19:11 2018] nvme nvme0: failed to connect queue: 2 ret=-18
> > >
> > >
> > > >
> > > > > maybe this is because of the bug that Steve mentioned in the NVMe
> > > > > mailing list. Sagi mentioned that we should fix it in the NVMe/RDMA
> > > > > initiator and I'll run his suggestion as well.
> > > >
> > > > Is your device irq affinity linear?
> > >
> > > When it's linear and the balancer is stopped the patch works.
> > >
> > > >
> > > > > BTW, when I run the blk_mq_map_queues it works for every irq affinity.
> > > >
> > > > But its probably not aligned to the device vector affinity.
> > >
> > > but I guess it's better in some cases.
> > >
> > > I've checked the situation before Leon's patch and set all the vetcors
> > > to CPU 0. In this case (I think that this was the initial report by
> > > Steve), we use the affinity_hint (Israel's and Saeed's patches were we
> > > use dev->priv.irq_info[vector].mask) and it worked fine.
> > >
> > > Steve,
> > > Can you share your configuration (kernel, HCA, affinity map, connect
> > > command, lscpu) ?
> > > I want to repro it in my lab.
> > >
> >
> > - linux-4.18-rc1 + the nvme/nvmet inline_data_size patches + patches to
> > enable ib_get_vector_affinity() in cxgb4 + sagi's patch + leon's mlx5
> > patch so I can change the affinity via procfs.
>
> ohh, now I understand that you where complaining regarding the affinity
> change reflection to mlx5_ib_get_vector_affinity and not regarding the
> failures on connecting while the affinity overlaps (that is working good
> before Leon's patch).
> So this is a known issue since we used a static hint that never changes
> from dev->priv.irq_info[vector].mask.
>
> IMO we must fulfil the user wish to connect to N queues and not reduce it
> because of affinity overlaps. So in order to push Leon's patch we must
> also fix the blk_mq_rdma_map_queues to do a best effort mapping according
> the affinity and map the rest in naive way (in that way we will *always*
> map all the queues).

Max,

I have no clue what is needed to do int blq_mq*, but my patch only gave
to users ability reconfigure their affinity mask after driver is loaded.

Thanks

>
> -Max.
>

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