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

[Stefano Stabellini <sstabellini@xxxxxxxxxx>]

On Wed, 15 Nov 2017, Paul Durrant wrote:
> Anthony, Stefano,
> 
>   Ping?

Acked-by: Stefano Stabellini <sstabellini@xxxxxxxxxx>

Unless Anthony or somebody else object, I'll queue it up in my "next"
branch (which I'll send upstream after 2.11 is out).

Cheers,

Stefano


> > -----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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