From 1b144e27fbbce3bae609b3092371fc11e8b12afc Mon Sep 17 00:00:00 2001 From: royger Date: Fri, 23 Oct 2015 15:46:42 +0000 Subject: [PATCH] blkfront: add support for unmapped IO Using unmapped IO is really beneficial when running inside of a VM, since it avoids IPIs to other vCPUs in order to invalidate the mappings. This patch adds unmapped IO support to blkfront. The following tests results have been obtained when running on a Xen host without HAP: PVHVM 3165.84 real 6354.17 user 4483.32 sys PVHVM with unmapped IO 2099.46 real 4624.52 user 2967.38 sys This is because when running using shadow page tables TLB flushes and range invalidations are much more expensive, so using unmapped IO provides a very important performance boost. Sponsored by: Citrix Systems R&D MFC after: 2 weeks X-MFC-with: r289834 --- sys/dev/xen/blkfront/blkfront.c | 12 +++++++----- 1 file changed, 7 insertions(+), 5 deletions(-) diff --git a/sys/dev/xen/blkfront/blkfront.c b/sys/dev/xen/blkfront/blkfront.c index fa8d479331b..0a75d79b1d2 100644 --- a/sys/dev/xen/blkfront/blkfront.c +++ b/sys/dev/xen/blkfront/blkfront.c @@ -293,8 +293,12 @@ xbd_queue_request(struct xbd_softc *sc, struct xbd_command *cm) { int error; - error = bus_dmamap_load(sc->xbd_io_dmat, cm->cm_map, cm->cm_data, - cm->cm_datalen, xbd_queue_cb, cm, 0); + if (cm->cm_bp != NULL) + error = bus_dmamap_load_bio(sc->xbd_io_dmat, cm->cm_map, + cm->cm_bp, xbd_queue_cb, cm, 0); + else + error = bus_dmamap_load(sc->xbd_io_dmat, cm->cm_map, + cm->cm_data, cm->cm_datalen, xbd_queue_cb, cm, 0); if (error == EINPROGRESS) { /* * Maintain queuing order by freezing the queue. The next @@ -354,8 +358,6 @@ xbd_bio_command(struct xbd_softc *sc) } cm->cm_bp = bp; - cm->cm_data = bp->bio_data; - cm->cm_datalen = bp->bio_bcount; cm->cm_sector_number = (blkif_sector_t)bp->bio_pblkno; switch (bp->bio_cmd) { @@ -1009,7 +1011,7 @@ xbd_instance_create(struct xbd_softc *sc, blkif_sector_t sectors, sc->xbd_disk->d_mediasize = sectors * sector_size; sc->xbd_disk->d_maxsize = sc->xbd_max_request_size; - sc->xbd_disk->d_flags = 0; + sc->xbd_disk->d_flags = DISKFLAG_UNMAPPED_BIO; if ((sc->xbd_flags & (XBDF_FLUSH|XBDF_BARRIER)) != 0) { sc->xbd_disk->d_flags |= DISKFLAG_CANFLUSHCACHE; device_printf(sc->xbd_dev, -- 2.39.5