Re: [Xen-devel] [PATCH v3] xen-disk: use an IOThread per instance

[Paul Durrant <Paul.Durrant@xxxxxxxxxx>]

Anthony, Stefano,

  Ping?

> -----Original Message-----
> From: Paul Durrant [mailto:paul.durrant@xxxxxxxxxx]
> Sent: 07 November 2017 10:47
> To: qemu-devel@xxxxxxxxxx; xen-devel@xxxxxxxxxxxxxxxxxxxx
> Cc: Paul Durrant <Paul.Durrant@xxxxxxxxxx>; Stefano Stabellini
> <sstabellini@xxxxxxxxxx>; Anthony Perard <anthony.perard@xxxxxxxxxx>;
> Kevin Wolf <kwolf@xxxxxxxxxx>; Max Reitz <mreitz@xxxxxxxxxx>
> Subject: [PATCH v3] xen-disk: use an IOThread per instance
> 
> This patch allocates an IOThread object for each xen_disk instance and
> sets the AIO context appropriately on connect. This allows processing
> of I/O to proceed in parallel.
> 
> The patch also adds tracepoints into xen_disk to make it possible to
> follow the state transtions of an instance in the log.
> 
> Signed-off-by: Paul Durrant <paul.durrant@xxxxxxxxxx>
> ---
> Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
> Cc: Anthony Perard <anthony.perard@xxxxxxxxxx>
> Cc: Kevin Wolf <kwolf@xxxxxxxxxx>
> Cc: Max Reitz <mreitz@xxxxxxxxxx>
> 
> v3:
>  - Use new iothread_create/destroy() functions
> 
> v2:
>  - explicitly acquire and release AIO context in qemu_aio_complete() and
>    blk_bh()
> ---
>  hw/block/trace-events |  7 +++++++
>  hw/block/xen_disk.c   | 53
> ++++++++++++++++++++++++++++++++++++++++++++-------
>  2 files changed, 53 insertions(+), 7 deletions(-)
> 
> diff --git a/hw/block/trace-events b/hw/block/trace-events
> index cb6767b3ee..962a3bfa24 100644
> --- a/hw/block/trace-events
> +++ b/hw/block/trace-events
> @@ -10,3 +10,10 @@ virtio_blk_submit_multireq(void *vdev, void *mrb, int
> start, int num_reqs, uint6
>  # hw/block/hd-geometry.c
>  hd_geometry_lchs_guess(void *blk, int cyls, int heads, int secs) "blk %p
> LCHS %d %d %d"
>  hd_geometry_guess(void *blk, uint32_t cyls, uint32_t heads, uint32_t secs,
> int trans) "blk %p CHS %u %u %u trans %d"
> +
> +# hw/block/xen_disk.c
> +xen_disk_alloc(char *name) "%s"
> +xen_disk_init(char *name) "%s"
> +xen_disk_connect(char *name) "%s"
> +xen_disk_disconnect(char *name) "%s"
> +xen_disk_free(char *name) "%s"
> diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c
> index e431bd89e8..f74fcd42d1 100644
> --- a/hw/block/xen_disk.c
> +++ b/hw/block/xen_disk.c
> @@ -27,10 +27,12 @@
>  #include "hw/xen/xen_backend.h"
>  #include "xen_blkif.h"
>  #include "sysemu/blockdev.h"
> +#include "sysemu/iothread.h"
>  #include "sysemu/block-backend.h"
>  #include "qapi/error.h"
>  #include "qapi/qmp/qdict.h"
>  #include "qapi/qmp/qstring.h"
> +#include "trace.h"
> 
>  /* ------------------------------------------------------------- */
> 
> @@ -125,6 +127,9 @@ struct XenBlkDev {
>      DriveInfo           *dinfo;
>      BlockBackend        *blk;
>      QEMUBH              *bh;
> +
> +    IOThread            *iothread;
> +    AioContext          *ctx;
>  };
> 
>  /* ------------------------------------------------------------- */
> @@ -596,9 +601,12 @@ static int ioreq_runio_qemu_aio(struct ioreq
> *ioreq);
>  static void qemu_aio_complete(void *opaque, int ret)
>  {
>      struct ioreq *ioreq = opaque;
> +    struct XenBlkDev *blkdev = ioreq->blkdev;
> +
> +    aio_context_acquire(blkdev->ctx);
> 
>      if (ret != 0) {
> -        xen_pv_printf(&ioreq->blkdev->xendev, 0, "%s I/O error\n",
> +        xen_pv_printf(&blkdev->xendev, 0, "%s I/O error\n",
>                        ioreq->req.operation == BLKIF_OP_READ ? "read" : 
> "write");
>          ioreq->aio_errors++;
>      }
> @@ -607,10 +615,10 @@ static void qemu_aio_complete(void *opaque, int
> ret)
>      if (ioreq->presync) {
>          ioreq->presync = 0;
>          ioreq_runio_qemu_aio(ioreq);
> -        return;
> +        goto done;
>      }
>      if (ioreq->aio_inflight > 0) {
> -        return;
> +        goto done;
>      }
> 
>      if (xen_feature_grant_copy) {
> @@ -647,16 +655,19 @@ static void qemu_aio_complete(void *opaque, int
> ret)
>          }
>      case BLKIF_OP_READ:
>          if (ioreq->status == BLKIF_RSP_OKAY) {
> -            block_acct_done(blk_get_stats(ioreq->blkdev->blk), &ioreq->acct);
> +            block_acct_done(blk_get_stats(blkdev->blk), &ioreq->acct);
>          } else {
> -            block_acct_failed(blk_get_stats(ioreq->blkdev->blk), 
> &ioreq->acct);
> +            block_acct_failed(blk_get_stats(blkdev->blk), &ioreq->acct);
>          }
>          break;
>      case BLKIF_OP_DISCARD:
>      default:
>          break;
>      }
> -    qemu_bh_schedule(ioreq->blkdev->bh);
> +    qemu_bh_schedule(blkdev->bh);
> +
> +done:
> +    aio_context_release(blkdev->ctx);
>  }
> 
>  static bool blk_split_discard(struct ioreq *ioreq, blkif_sector_t
> sector_number,
> @@ -913,17 +924,29 @@ static void blk_handle_requests(struct XenBlkDev
> *blkdev)
>  static void blk_bh(void *opaque)
>  {
>      struct XenBlkDev *blkdev = opaque;
> +
> +    aio_context_acquire(blkdev->ctx);
>      blk_handle_requests(blkdev);
> +    aio_context_release(blkdev->ctx);
>  }
> 
>  static void blk_alloc(struct XenDevice *xendev)
>  {
>      struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev,
> xendev);
> +    Error *err = NULL;
> +
> +    trace_xen_disk_alloc(xendev->name);
> 
>      QLIST_INIT(&blkdev->inflight);
>      QLIST_INIT(&blkdev->finished);
>      QLIST_INIT(&blkdev->freelist);
> -    blkdev->bh = qemu_bh_new(blk_bh, blkdev);
> +
> +    blkdev->iothread = iothread_create(xendev->name, &err);
> +    assert(!err);
> +
> +    blkdev->ctx = iothread_get_aio_context(blkdev->iothread);
> +    blkdev->bh = aio_bh_new(blkdev->ctx, blk_bh, blkdev);
> +
>      if (xen_mode != XEN_EMULATE) {
>          batch_maps = 1;
>      }
> @@ -950,6 +973,8 @@ static int blk_init(struct XenDevice *xendev)
>      int info = 0;
>      char *directiosafe = NULL;
> 
> +    trace_xen_disk_init(xendev->name);
> +
>      /* read xenstore entries */
>      if (blkdev->params == NULL) {
>          char *h = NULL;
> @@ -1062,6 +1087,8 @@ static int blk_connect(struct XenDevice *xendev)
>      unsigned int i;
>      uint32_t *domids;
> 
> +    trace_xen_disk_connect(xendev->name);
> +
>      /* read-only ? */
>      if (blkdev->directiosafe) {
>          qflags = BDRV_O_NOCACHE | BDRV_O_NATIVE_AIO;
> @@ -1287,6 +1314,8 @@ static int blk_connect(struct XenDevice *xendev)
>          blkdev->persistent_gnt_count = 0;
>      }
> 
> +    blk_set_aio_context(blkdev->blk, blkdev->ctx);
> +
>      xen_be_bind_evtchn(&blkdev->xendev);
> 
>      xen_pv_printf(&blkdev->xendev, 1, "ok: proto %s, nr-ring-ref %u, "
> @@ -1300,13 +1329,20 @@ static void blk_disconnect(struct XenDevice
> *xendev)
>  {
>      struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev,
> xendev);
> 
> +    trace_xen_disk_disconnect(xendev->name);
> +
> +    aio_context_acquire(blkdev->ctx);
> +
>      if (blkdev->blk) {
> +        blk_set_aio_context(blkdev->blk, qemu_get_aio_context());
>          blk_detach_dev(blkdev->blk, blkdev);
>          blk_unref(blkdev->blk);
>          blkdev->blk = NULL;
>      }
>      xen_pv_unbind_evtchn(&blkdev->xendev);
> 
> +    aio_context_release(blkdev->ctx);
> +
>      if (blkdev->sring) {
>          xengnttab_unmap(blkdev->xendev.gnttabdev, blkdev->sring,
>                          blkdev->nr_ring_ref);
> @@ -1345,6 +1381,8 @@ static int blk_free(struct XenDevice *xendev)
>      struct XenBlkDev *blkdev = container_of(xendev, struct XenBlkDev,
> xendev);
>      struct ioreq *ioreq;
> 
> +    trace_xen_disk_free(xendev->name);
> +
>      blk_disconnect(xendev);
> 
>      while (!QLIST_EMPTY(&blkdev->freelist)) {
> @@ -1360,6 +1398,7 @@ static int blk_free(struct XenDevice *xendev)
>      g_free(blkdev->dev);
>      g_free(blkdev->devtype);
>      qemu_bh_delete(blkdev->bh);
> +    iothread_destroy(blkdev->iothread);
>      return 0;
>  }
> 
> --
> 2.11.0


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