Date: Thu, 1 Feb 2018 16:52:03 +0000 (UTC) From: Alexander Motin <mav@FreeBSD.org> To: src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-stable@freebsd.org, svn-src-stable-11@freebsd.org Subject: svn commit: r328691 - stable/11/sys/dev/nvme Message-ID: <201802011652.w11Gq3Zh031059@repo.freebsd.org>
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Author: mav Date: Thu Feb 1 16:52:03 2018 New Revision: 328691 URL: https://svnweb.freebsd.org/changeset/base/328691 Log: MFC r322994: Set the max transactions for NVMe drives better. Provided a better estimate for the number of transactions that can be pending at one time. This will be number of queues * number of trackers / 4, as suggested by Jim Harris. This gives a better estimate of the number of transactions that CAM should queue before applying back pressure. This should be revisted when we have real multi-queue support in CAM and the upper layers of the I/O stack. Modified: stable/11/sys/dev/nvme/nvme_ctrlr.c stable/11/sys/dev/nvme/nvme_private.h stable/11/sys/dev/nvme/nvme_sim.c Directory Properties: stable/11/ (props changed) Modified: stable/11/sys/dev/nvme/nvme_ctrlr.c ============================================================================== --- stable/11/sys/dev/nvme/nvme_ctrlr.c Thu Feb 1 16:51:11 2018 (r328690) +++ stable/11/sys/dev/nvme/nvme_ctrlr.c Thu Feb 1 16:52:03 2018 (r328691) @@ -146,6 +146,14 @@ nvme_ctrlr_construct_io_qpairs(struct nvme_controller num_trackers = min(num_trackers, (num_entries-1)); /* + * Our best estimate for the maximum number of I/Os that we should + * noramlly have in flight at one time. This should be viewed as a hint, + * not a hard limit and will need to be revisitted when the upper layers + * of the storage system grows multi-queue support. + */ + ctrlr->max_hw_pend_io = num_trackers * ctrlr->num_io_queues / 4; + + /* * This was calculated previously when setting up interrupts, but * a controller could theoretically support fewer I/O queues than * MSI-X vectors. So calculate again here just to be safe. Modified: stable/11/sys/dev/nvme/nvme_private.h ============================================================================== --- stable/11/sys/dev/nvme/nvme_private.h Thu Feb 1 16:51:11 2018 (r328690) +++ stable/11/sys/dev/nvme/nvme_private.h Thu Feb 1 16:52:03 2018 (r328691) @@ -263,6 +263,7 @@ struct nvme_controller { uint32_t num_io_queues; uint32_t num_cpus_per_ioq; + uint32_t max_hw_pend_io; /* Fields for tracking progress during controller initialization. */ struct intr_config_hook config_hook; Modified: stable/11/sys/dev/nvme/nvme_sim.c ============================================================================== --- stable/11/sys/dev/nvme/nvme_sim.c Thu Feb 1 16:51:11 2018 (r328690) +++ stable/11/sys/dev/nvme/nvme_sim.c Thu Feb 1 16:52:03 2018 (r328691) @@ -261,7 +261,7 @@ nvme_sim_new_controller(struct nvme_controller *ctrlr) int unit; struct nvme_sim_softc *sc = NULL; - max_trans = ctrlr->num_io_queues; + max_trans = ctrlr->max_hw_pend_io; unit = device_get_unit(ctrlr->dev); devq = cam_simq_alloc(max_trans); if (devq == NULL)
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