Re: [PATCH 1/1] Revert "RDMA/rxe: Add workqueue support for rxe tasks"

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On Wed, Sep 27, 2023 at 4:37 AM Bart Van Assche <bvanassche@xxxxxxx> wrote:
>
> On 9/26/23 11:34, Bob Pearson wrote:
> > I am working to try to reproduce the KASAN warning. Unfortunately,
> > so far I am not able to see it in Ubuntu + Linus' kernel (as you
> > described) on metal. The config file is different but copies the
> > CONFIG_KASAN_xxx exactly as yours. With KASAN enabled it hangs on
> > every iteration of srp/002 but without a KASAN warning. I am now
> > building an openSuSE VM for qemu and will see if that causes the
> > warning.
>
> Hi Bob,
>
> Did you try to understand the report that I shared? My conclusion from
> the report is that when using tasklets rxe_completer() only runs after
> rxe_requester() has finished and also that when using work queues that
> rxe_completer() may run concurrently with rxe_requester(). This patch
> seems to fix all issues that I ran into with the rdma_rxe workqueue
> patch (I have not tried to verify the performance implications of this
> patch):

In the same test environment in the link
https://lore.kernel.org/all/4e7aac82-f006-aaa7-6769-d1c9691a0cec@xxxxxxxxx/T/#m3294d00f5cf3247dfdb2ea3688b1467167f72704,

RXE with workqueue has worse performance than RXE with tasklet.
Sometimes RXE with workqueue can not work well.

Need this commit in RXE.

>
> diff --git a/drivers/infiniband/sw/rxe/rxe_task.c
> b/drivers/infiniband/sw/rxe/rxe_task.c
> index 1501120d4f52..6cd5d5a7a316 100644
> --- a/drivers/infiniband/sw/rxe/rxe_task.c
> +++ b/drivers/infiniband/sw/rxe/rxe_task.c
> @@ -10,7 +10,7 @@ static struct workqueue_struct *rxe_wq;
>
>   int rxe_alloc_wq(void)
>   {
> -       rxe_wq = alloc_workqueue("rxe_wq", WQ_UNBOUND, WQ_MAX_ACTIVE);
> +       rxe_wq = alloc_workqueue("rxe_wq", WQ_UNBOUND, 1);
>          if (!rxe_wq)
>                  return -ENOMEM;
>
> Thanks,
>
> Bart.




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