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[Qemu-devel] [RFC v9 20/27] virtio-blk: Add ioscheduler to detect mergab
From: |
Stefan Hajnoczi |
Subject: |
[Qemu-devel] [RFC v9 20/27] virtio-blk: Add ioscheduler to detect mergable requests |
Date: |
Wed, 18 Jul 2012 16:07:47 +0100 |
---
hw/dataplane/iosched.h | 78 ++++++++++++++++++++++++++++++++++++++++++++++++
hw/virtio-blk.c | 5 ++++
2 files changed, 83 insertions(+)
create mode 100644 hw/dataplane/iosched.h
diff --git a/hw/dataplane/iosched.h b/hw/dataplane/iosched.h
new file mode 100644
index 0000000..12ebccc
--- /dev/null
+++ b/hw/dataplane/iosched.h
@@ -0,0 +1,78 @@
+#ifndef IOSCHED_H
+#define IOSCHED_H
+
+#include "hw/dataplane/ioq.h"
+
+typedef struct {
+ unsigned long iocbs;
+ unsigned long merges;
+ unsigned long sched_calls;
+} IOSched;
+
+static int iocb_cmp(const void *a, const void *b)
+{
+ const struct iocb *iocb_a = a;
+ const struct iocb *iocb_b = b;
+
+ /*
+ * Note that we can't simply subtract req2->sector from req1->sector
+ * here as that could overflow the return value.
+ */
+ if (iocb_a->u.c.offset > iocb_b->u.c.offset) {
+ return 1;
+ } else if (iocb_a->u.c.offset < iocb_b->u.c.offset) {
+ return -1;
+ } else {
+ return 0;
+ }
+}
+
+static size_t iocb_nbytes(struct iocb *iocb)
+{
+ struct iovec *iov = iocb->u.c.buf;
+ size_t nbytes = 0;
+ size_t i;
+ for (i = 0; i < iocb->u.c.nbytes; i++) {
+ nbytes += iov->iov_len;
+ iov++;
+ }
+ return nbytes;
+}
+
+static void iosched_init(IOSched *iosched)
+{
+ memset(iosched, 0, sizeof *iosched);
+}
+
+static void iosched_print_stats(IOSched *iosched)
+{
+ fprintf(stderr, "iocbs = %lu merges = %lu sched_calls = %lu\n",
+ iosched->iocbs, iosched->merges, iosched->sched_calls);
+ memset(iosched, 0, sizeof *iosched);
+}
+
+static void iosched(IOSched *iosched, struct iocb *unsorted[], unsigned int
count)
+{
+ struct iocb *sorted[count];
+ struct iocb *last;
+ unsigned int i;
+
+ if ((++iosched->sched_calls % 1000) == 0) {
+ iosched_print_stats(iosched);
+ }
+
+ memcpy(sorted, unsorted, sizeof sorted);
+ qsort(sorted, count, sizeof sorted[0], iocb_cmp);
+
+ iosched->iocbs += count;
+ last = sorted[0];
+ for (i = 1; i < count; i++) {
+ if (last->aio_lio_opcode == sorted[i]->aio_lio_opcode &&
+ last->u.c.offset + iocb_nbytes(last) == sorted[i]->u.c.offset) {
+ iosched->merges++;
+ }
+ last = sorted[i];
+ }
+}
+
+#endif /* IOSCHED_H */
diff --git a/hw/virtio-blk.c b/hw/virtio-blk.c
index f67fdb7..75cb0f2 100644
--- a/hw/virtio-blk.c
+++ b/hw/virtio-blk.c
@@ -22,6 +22,7 @@
#include "hw/dataplane/event-poll.h"
#include "hw/dataplane/vring.h"
#include "hw/dataplane/ioq.h"
+#include "hw/dataplane/iosched.h"
#include "kvm.h"
enum {
@@ -57,6 +58,7 @@ typedef struct {
EventHandler notify_handler; /* virtqueue notify handler */
IOQueue ioqueue; /* Linux AIO queue (should really be per
dataplane thread) */
+ IOSched iosched; /* I/O scheduler */
VirtIOBlockRequest requests[REQ_MAX]; /* pool of requests, managed by the
queue */
} VirtIOBlock;
@@ -249,6 +251,8 @@ static bool handle_notify(EventHandler *handler)
}
}
+ iosched(&s->iosched, s->ioqueue.queue, s->ioqueue.queue_idx);
+
/* Submit requests, if any */
int rc = ioq_submit(&s->ioqueue);
if (unlikely(rc < 0)) {
@@ -289,6 +293,7 @@ static void data_plane_start(VirtIOBlock *s)
{
int i;
+ iosched_init(&s->iosched);
vring_setup(&s->vring, &s->vdev, 0);
/* Set up guest notifier (irq) */
--
1.7.10.4
- Re: [Qemu-devel] [RFC v9 12/27] virtio-blk: Add workaround for BUG_ON() dependency in virtio_ring.h, (continued)
- [Qemu-devel] [RFC v9 11/27] virtio-blk: Indirect vring and flush support, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 14/27] virtio-blk: Use pthreads instead of qemu-thread, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 16/27] virtio-blk: Kick data plane thread using event notifier set, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 08/27] virtio-blk: Read requests from the vring, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 18/27] virtio-blk: Call ioctl() directly instead of irqfd, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 21/27] virtio-blk: Add basic request merging, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 20/27] virtio-blk: Add ioscheduler to detect mergable requests,
Stefan Hajnoczi <=
- [Qemu-devel] [RFC v9 26/27] msix: use upstream kvm_irqchip_set_irq(), Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 19/27] virtio-blk: Disable guest->host notifies while processing vring, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 27/27] virtio-blk: add EVENT_IDX support to dataplane, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 24/27] virtio-blk: fix incorrect length, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 17/27] virtio-blk: Use guest notifier to raise interrupts, Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 25/27] msix: fix irqchip breakage in msix_try_notify_from_thread(), Stefan Hajnoczi, 2012/07/18
- [Qemu-devel] [RFC v9 22/27] virtio-blk: Fix request merging, Stefan Hajnoczi, 2012/07/18
- Re: [Qemu-devel] [RFC v9 00/27] virtio: virtio-blk data plane, Michael S. Tsirkin, 2012/07/18