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Date: Wed, 15 Feb 2017 07:26:37 -0800 From: Eric Dumazet <eric.dumazet@...il.com> To: "Matan Barak (External)" <matanb@...lanox.com> Cc: Saeed Mahameed <saeedm@....mellanox.co.il>, David Miller <davem@...emloft.net>, netdev <netdev@...r.kernel.org>, Tariq Toukan <tariqt@...lanox.com>, Saeed Mahameed <saeedm@...lanox.com>, jackm@...lanox.com Subject: Re: [PATCH net-next] mlx4: do not fire tasklet unless necessary On Wed, 2017-02-15 at 16:52 +0200, Matan Barak (External) wrote: > So, in case of RDMA CQs, we add some per-CQE overhead of comparing the > list pointers and condition upon that. Maybe we could add an > invoke_tasklet boolean field on mlx4_cq and return its value from > mlx4_cq_completion. > That's way we could do invoke_tasklet |= mlx4_cq_completion(....); > > Outside the while loop we could just > if (invoke_tasklet) > tasklet_schedule > > Anyway, I guess that even with per-CQE overhead, the performance impact > here is pretty negligible - so I guess that's fine too :) Real question or suggestion would be to use/fire a tasklet only under stress. Firing a tasklet adds a lot of latencies for user-space CQ completion, since softirqs might have to be handled by a kernel thread (ksoftirqd) I would be surprised if no customer was hit by your commit, ( net/mlx4_core: Use tasklet for user-space CQ completion events ) especially when using specific (RT) scheduler classes.
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