From mboxrd@z Thu Jan 1 00:00:00 1970 From: Sagi Grimberg Subject: Re: [PATCH 2/9] IB: add a proper completion queue abstraction Date: Wed, 18 Nov 2015 09:55:45 +0200 Message-ID: <564C2F01.6020407@dev.mellanox.co.il> References: <1447422410-20891-1-git-send-email-hch@lst.de> <1447422410-20891-3-git-send-email-hch@lst.de> <564B697A.2020601@sandisk.com> Mime-Version: 1.0 Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <564B697A.2020601-XdAiOPVOjttBDgjK7y7TUQ@public.gmane.org> Sender: linux-rdma-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org To: Bart Van Assche , Christoph Hellwig , linux-rdma-u79uwXL29TY76Z2rM5mHXA@public.gmane.org Cc: axboe-b10kYP2dOMg@public.gmane.org, linux-scsi-u79uwXL29TY76Z2rM5mHXA@public.gmane.org, linux-kernel-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-Id: linux-rdma@vger.kernel.org Hi Bart, >> + */ >> +void ib_process_cq_direct(struct ib_cq *cq) >> +{ >> + WARN_ON_ONCE(cq->poll_ctx != IB_POLL_DIRECT); >> + >> + __ib_process_cq(cq, INT_MAX); >> +} >> +EXPORT_SYMBOL(ib_process_cq_direct); > > My proposal is to drop this function and to export __ib_process_cq() > instead (with or without renaming). That will allow callers of this > function to compare the poll budget with the number of completions that > have been processed and use that information to decide whether or not to > call this function again. I agree with that. > >> +static void ib_cq_poll_work(struct work_struct *work) >> +{ >> + struct ib_cq *cq = container_of(work, struct ib_cq, work); >> + int completed; >> + >> + completed = __ib_process_cq(cq, IB_POLL_BUDGET_WORKQUEUE); >> + if (completed >= IB_POLL_BUDGET_WORKQUEUE || >> + ib_req_notify_cq(cq, IB_POLL_FLAGS) > 0) >> + queue_work(ib_comp_wq, &cq->work); >> +} >> + >> +static void ib_cq_completion_workqueue(struct ib_cq *cq, void *private) >> +{ >> + queue_work(ib_comp_wq, &cq->work); >> +} > > The above code will cause all polling to occur on the context of the CPU > that received the completion interrupt. This approach is not powerful > enough. For certain workloads throughput is higher if work completions > are processed by another CPU core on the same CPU socket. Has it been > considered to make the CPU core on which work completions are processed > configurable ? The workqueue is unbound. This means that the functionality you are you are asking for exists. -- To unsubscribe from this list: send the line "unsubscribe linux-rdma" in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html