| Message ID | 1525442134-20488-8-git-send-email-paul.durrant@citrix.com (mailing list archive) |
|---|---|
| State | New, archived |
| Headers | show |
> -----Original Message----- > From: Paul Durrant [mailto:paul.durrant@citrix.com] > Sent: 04 May 2018 14:56 > To: xen-devel@lists.xenproject.org; qemu-block@nongnu.org; qemu- > devel@nongnu.org > Cc: Paul Durrant <Paul.Durrant@citrix.com>; Stefano Stabellini > <sstabellini@kernel.org>; Anthony Perard <anthony.perard@citrix.com>; > Kevin Wolf <kwolf@redhat.com>; Max Reitz <mreitz@redhat.com> > Subject: [PATCH v2 7/8] xen_disk: use a single entry iovec > > Since xen_disk now always copies data to and from a guest there is no need > to maintain a vector entry corresponding to every page of a request. > This means there is less per-request state to maintain so the ioreq > structure can shrink significantly. > > Signed-off-by: Paul Durrant <paul.durrant@citrix.com> > --- > Cc: Stefano Stabellini <sstabellini@kernel.org> > Cc: Anthony Perard <anthony.perard@citrix.com> > Cc: Kevin Wolf <kwolf@redhat.com> > Cc: Max Reitz <mreitz@redhat.com> > > v2: > - Re-based Unfortunately I managed to drop a hunk during rebase and so this patch is actually broken. I'll send a rectified v3 shortly. Paul > --- > hw/block/xen_disk.c | 71 ++++++++++++++--------------------------------------- > 1 file changed, 18 insertions(+), 53 deletions(-) > > diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c > index 28be8b6..230961f 100644 > --- a/hw/block/xen_disk.c > +++ b/hw/block/xen_disk.c > @@ -46,13 +46,10 @@ struct ioreq { > /* parsed request */ > off_t start; > QEMUIOVector v; > + void *buf; > + size_t size; > int presync; > > - /* grant mapping */ > - uint32_t refs[BLKIF_MAX_SEGMENTS_PER_REQUEST]; > - void *page[BLKIF_MAX_SEGMENTS_PER_REQUEST]; > - void *pages; > - > /* aio status */ > int aio_inflight; > int aio_errors; > @@ -110,12 +107,10 @@ static void ioreq_reset(struct ioreq *ioreq) > memset(&ioreq->req, 0, sizeof(ioreq->req)); > ioreq->status = 0; > ioreq->start = 0; > + ioreq->buf = NULL; > + ioreq->size = 0; > ioreq->presync = 0; > > - memset(ioreq->refs, 0, sizeof(ioreq->refs)); > - memset(ioreq->page, 0, sizeof(ioreq->page)); > - ioreq->pages = NULL; > - > ioreq->aio_inflight = 0; > ioreq->aio_errors = 0; > > @@ -138,7 +133,7 @@ static struct ioreq *ioreq_start(struct XenBlkDev > *blkdev) > ioreq = g_malloc0(sizeof(*ioreq)); > ioreq->blkdev = blkdev; > blkdev->requests_total++; > - qemu_iovec_init(&ioreq->v, BLKIF_MAX_SEGMENTS_PER_REQUEST); > + qemu_iovec_init(&ioreq->v, 1); > } else { > /* get one from freelist */ > ioreq = QLIST_FIRST(&blkdev->freelist); > @@ -183,7 +178,6 @@ static void ioreq_release(struct ioreq *ioreq, bool > finish) > static int ioreq_parse(struct ioreq *ioreq) > { > struct XenBlkDev *blkdev = ioreq->blkdev; > - uintptr_t mem; > size_t len; > int i; > > @@ -230,13 +224,10 @@ static int ioreq_parse(struct ioreq *ioreq) > goto err; > } > > - ioreq->refs[i] = ioreq->req.seg[i].gref; > - > - mem = ioreq->req.seg[i].first_sect * blkdev->file_blk; > len = (ioreq->req.seg[i].last_sect - ioreq->req.seg[i].first_sect + 1) * > blkdev->file_blk; > - qemu_iovec_add(&ioreq->v, (void*)mem, len); > + ioreq->size += len; > } > - if (ioreq->start + ioreq->v.size > blkdev->file_size) { > + if (ioreq->start + ioreq->size > blkdev->file_size) { > xen_pv_printf(&blkdev->xendev, 0, "error: access beyond end of > file\n"); > goto err; > } > @@ -247,35 +238,6 @@ err: > return -1; > } > > -static void ioreq_free_copy_buffers(struct ioreq *ioreq) > -{ > - int i; > - > - for (i = 0; i < ioreq->v.niov; i++) { > - ioreq->page[i] = NULL; > - } > - > - qemu_vfree(ioreq->pages); > -} > - > -static int ioreq_init_copy_buffers(struct ioreq *ioreq) > -{ > - int i; > - > - if (ioreq->v.niov == 0) { > - return 0; > - } > - > - ioreq->pages = qemu_memalign(XC_PAGE_SIZE, ioreq->v.niov * > XC_PAGE_SIZE); > - > - for (i = 0; i < ioreq->v.niov; i++) { > - ioreq->page[i] = ioreq->pages + i * XC_PAGE_SIZE; > - ioreq->v.iov[i].iov_base = ioreq->page[i]; > - } > - > - return 0; > -} > - > static int ioreq_grant_copy(struct ioreq *ioreq) > { > struct XenBlkDev *blkdev = ioreq->blkdev; > @@ -284,6 +246,7 @@ static int ioreq_grant_copy(struct ioreq *ioreq) > int i, count, rc; > int64_t file_blk = ioreq->blkdev->file_blk; > bool to_domain = (ioreq->req.operation == BLKIF_OP_READ); > + void *virt = ioreq->buf; > > if (ioreq->v.niov == 0) { > return 0; > @@ -293,16 +256,17 @@ static int ioreq_grant_copy(struct ioreq *ioreq) > > for (i = 0; i < count; i++) { > if (to_domain) { > - segs[i].dest.foreign.ref = ioreq->refs[i]; > + segs[i].dest.foreign.ref = ioreq->req.seg[i].gref; > segs[i].dest.foreign.offset = ioreq->req.seg[i].first_sect * file_blk; > - segs[i].source.virt = ioreq->v.iov[i].iov_base; > + segs[i].source.virt = virt; > } else { > - segs[i].source.foreign.ref = ioreq->refs[i]; > + segs[i].source.foreign.ref = ioreq->req.seg[i].gref; > segs[i].source.foreign.offset = ioreq->req.seg[i].first_sect * file_blk; > - segs[i].dest.virt = ioreq->v.iov[i].iov_base; > + segs[i].dest.virt = virt; > } > segs[i].len = (ioreq->req.seg[i].last_sect > - ioreq->req.seg[i].first_sect + 1) * file_blk; > + virt += segs[i].len; > } > > rc = xen_be_copy_grant_refs(xendev, to_domain, segs, count); > @@ -314,6 +278,7 @@ static int ioreq_grant_copy(struct ioreq *ioreq) > return -1; > } > > + qemu_iovec_add(&ioreq->v, ioreq->buf, ioreq->size); > return rc; > } > > @@ -348,14 +313,14 @@ static void qemu_aio_complete(void *opaque, int > ret) > if (ret == 0) { > ioreq_grant_copy(ioreq); > } > - ioreq_free_copy_buffers(ioreq); > + qemu_vfree(ioreq->buf); > break; > case BLKIF_OP_WRITE: > case BLKIF_OP_FLUSH_DISKCACHE: > if (!ioreq->req.nr_segments) { > break; > } > - ioreq_free_copy_buffers(ioreq); > + qemu_vfree(ioreq->buf); > break; > default: > break; > @@ -423,12 +388,12 @@ static int ioreq_runio_qemu_aio(struct ioreq > *ioreq) > { > struct XenBlkDev *blkdev = ioreq->blkdev; > > - ioreq_init_copy_buffers(ioreq); > + ioreq->buf = qemu_memalign(XC_PAGE_SIZE, ioreq->size); > if (ioreq->req.nr_segments && > (ioreq->req.operation == BLKIF_OP_WRITE || > ioreq->req.operation == BLKIF_OP_FLUSH_DISKCACHE) && > ioreq_grant_copy(ioreq)) { > - ioreq_free_copy_buffers(ioreq); > + qemu_vfree(ioreq->buf); > goto err; > } > > -- > 2.1.4
diff --git a/hw/block/xen_disk.c b/hw/block/xen_disk.c index 28be8b6..230961f 100644 --- a/hw/block/xen_disk.c +++ b/hw/block/xen_disk.c @@ -46,13 +46,10 @@ struct ioreq { /* parsed request */ off_t start; QEMUIOVector v; + void *buf; + size_t size; int presync; - /* grant mapping */ - uint32_t refs[BLKIF_MAX_SEGMENTS_PER_REQUEST]; - void *page[BLKIF_MAX_SEGMENTS_PER_REQUEST]; - void *pages; - /* aio status */ int aio_inflight; int aio_errors; @@ -110,12 +107,10 @@ static void ioreq_reset(struct ioreq *ioreq) memset(&ioreq->req, 0, sizeof(ioreq->req)); ioreq->status = 0; ioreq->start = 0; + ioreq->buf = NULL; + ioreq->size = 0; ioreq->presync = 0; - memset(ioreq->refs, 0, sizeof(ioreq->refs)); - memset(ioreq->page, 0, sizeof(ioreq->page)); - ioreq->pages = NULL; - ioreq->aio_inflight = 0; ioreq->aio_errors = 0; @@ -138,7 +133,7 @@ static struct ioreq *ioreq_start(struct XenBlkDev *blkdev) ioreq = g_malloc0(sizeof(*ioreq)); ioreq->blkdev = blkdev; blkdev->requests_total++; - qemu_iovec_init(&ioreq->v, BLKIF_MAX_SEGMENTS_PER_REQUEST); + qemu_iovec_init(&ioreq->v, 1); } else { /* get one from freelist */ ioreq = QLIST_FIRST(&blkdev->freelist); @@ -183,7 +178,6 @@ static void ioreq_release(struct ioreq *ioreq, bool finish) static int ioreq_parse(struct ioreq *ioreq) { struct XenBlkDev *blkdev = ioreq->blkdev; - uintptr_t mem; size_t len; int i; @@ -230,13 +224,10 @@ static int ioreq_parse(struct ioreq *ioreq) goto err; } - ioreq->refs[i] = ioreq->req.seg[i].gref; - - mem = ioreq->req.seg[i].first_sect * blkdev->file_blk; len = (ioreq->req.seg[i].last_sect - ioreq->req.seg[i].first_sect + 1) * blkdev->file_blk; - qemu_iovec_add(&ioreq->v, (void*)mem, len); + ioreq->size += len; } - if (ioreq->start + ioreq->v.size > blkdev->file_size) { + if (ioreq->start + ioreq->size > blkdev->file_size) { xen_pv_printf(&blkdev->xendev, 0, "error: access beyond end of file\n"); goto err; } @@ -247,35 +238,6 @@ err: return -1; } -static void ioreq_free_copy_buffers(struct ioreq *ioreq) -{ - int i; - - for (i = 0; i < ioreq->v.niov; i++) { - ioreq->page[i] = NULL; - } - - qemu_vfree(ioreq->pages); -} - -static int ioreq_init_copy_buffers(struct ioreq *ioreq) -{ - int i; - - if (ioreq->v.niov == 0) { - return 0; - } - - ioreq->pages = qemu_memalign(XC_PAGE_SIZE, ioreq->v.niov * XC_PAGE_SIZE); - - for (i = 0; i < ioreq->v.niov; i++) { - ioreq->page[i] = ioreq->pages + i * XC_PAGE_SIZE; - ioreq->v.iov[i].iov_base = ioreq->page[i]; - } - - return 0; -} - static int ioreq_grant_copy(struct ioreq *ioreq) { struct XenBlkDev *blkdev = ioreq->blkdev; @@ -284,6 +246,7 @@ static int ioreq_grant_copy(struct ioreq *ioreq) int i, count, rc; int64_t file_blk = ioreq->blkdev->file_blk; bool to_domain = (ioreq->req.operation == BLKIF_OP_READ); + void *virt = ioreq->buf; if (ioreq->v.niov == 0) { return 0; @@ -293,16 +256,17 @@ static int ioreq_grant_copy(struct ioreq *ioreq) for (i = 0; i < count; i++) { if (to_domain) { - segs[i].dest.foreign.ref = ioreq->refs[i]; + segs[i].dest.foreign.ref = ioreq->req.seg[i].gref; segs[i].dest.foreign.offset = ioreq->req.seg[i].first_sect * file_blk; - segs[i].source.virt = ioreq->v.iov[i].iov_base; + segs[i].source.virt = virt; } else { - segs[i].source.foreign.ref = ioreq->refs[i]; + segs[i].source.foreign.ref = ioreq->req.seg[i].gref; segs[i].source.foreign.offset = ioreq->req.seg[i].first_sect * file_blk; - segs[i].dest.virt = ioreq->v.iov[i].iov_base; + segs[i].dest.virt = virt; } segs[i].len = (ioreq->req.seg[i].last_sect - ioreq->req.seg[i].first_sect + 1) * file_blk; + virt += segs[i].len; } rc = xen_be_copy_grant_refs(xendev, to_domain, segs, count); @@ -314,6 +278,7 @@ static int ioreq_grant_copy(struct ioreq *ioreq) return -1; } + qemu_iovec_add(&ioreq->v, ioreq->buf, ioreq->size); return rc; } @@ -348,14 +313,14 @@ static void qemu_aio_complete(void *opaque, int ret) if (ret == 0) { ioreq_grant_copy(ioreq); } - ioreq_free_copy_buffers(ioreq); + qemu_vfree(ioreq->buf); break; case BLKIF_OP_WRITE: case BLKIF_OP_FLUSH_DISKCACHE: if (!ioreq->req.nr_segments) { break; } - ioreq_free_copy_buffers(ioreq); + qemu_vfree(ioreq->buf); break; default: break; @@ -423,12 +388,12 @@ static int ioreq_runio_qemu_aio(struct ioreq *ioreq) { struct XenBlkDev *blkdev = ioreq->blkdev; - ioreq_init_copy_buffers(ioreq); + ioreq->buf = qemu_memalign(XC_PAGE_SIZE, ioreq->size); if (ioreq->req.nr_segments && (ioreq->req.operation == BLKIF_OP_WRITE || ioreq->req.operation == BLKIF_OP_FLUSH_DISKCACHE) && ioreq_grant_copy(ioreq)) { - ioreq_free_copy_buffers(ioreq); + qemu_vfree(ioreq->buf); goto err; }
Since xen_disk now always copies data to and from a guest there is no need to maintain a vector entry corresponding to every page of a request. This means there is less per-request state to maintain so the ioreq structure can shrink significantly. Signed-off-by: Paul Durrant <paul.durrant@citrix.com> --- Cc: Stefano Stabellini <sstabellini@kernel.org> Cc: Anthony Perard <anthony.perard@citrix.com> Cc: Kevin Wolf <kwolf@redhat.com> Cc: Max Reitz <mreitz@redhat.com> v2: - Re-based --- hw/block/xen_disk.c | 71 ++++++++++++++--------------------------------------- 1 file changed, 18 insertions(+), 53 deletions(-)