| Message ID | 1455954883-28858-2-git-send-email-den@openvz.org |
|---|---|
| State | New |
| Headers | show |
On 02/20/2016 12:54 AM, Denis V. Lunev wrote: > From: Igor Redko <redkoi@virtuozzo.com> > > We are making experiments with different autoballooning strategies > based on the guest behavior. Thus we need to experiment with different > guest statistics. For now every counter change requires QEMU recompilation > and dances with Libvirt. > > This patch introduces transport for unrecognized counters in virtio-balloon. > This transport can be used for measuring benefits from using new > balloon counters, before submitting any patches. Current alternative > is 'guest-exec' transport which isn't made for such delicate matters > and can influence test results. > > Originally all counters with tag >= VIRTIO_BALLOON_S_NR were ignored. > Instead of this we keep first (VIRTIO_BALLOON_S_NR + 32) counters from the > queue and pass unrecognized ones with the following names: 'x-stat-XXXX', > where XXXX is a tag number in hex. Defined counters are reported with their > regular names. The name implies experimental, so apps like libvirt shouldn't rely on it; while it does fill a gap for making development easier, so I'm in favor of the idea. > @@ -133,12 +132,20 @@ static void balloon_stats_get_all(Object *obj, Visitor *v, const char *name, > if (err) { > goto out_end; > } > - for (i = 0; i < VIRTIO_BALLOON_S_NR; i++) { > - visit_type_uint64(v, balloon_stat_names[i], &s->stats[i], &err); > + for (i = 0; !err && i < s->stats_cnt; i++) { Why are you checking for err here? You cannot enter the loop with err set... > + if (s->stats[i].tag < VIRTIO_BALLOON_S_NR) { > + visit_type_uint64(v, balloon_stat_names[s->stats[i].tag], > + &s->stats[i].val, &err); > + } else { > + gchar *str = g_strdup_printf("x-stat-%04x", s->stats[i].tag); > + visit_type_uint64(v, str, &s->stats[i].val, &err); > + g_free(str); > + } > if (err) { > break; > } ...and you cannot exit the loop with it set. Therefore the check is dead code.
diff --git a/hw/virtio/virtio-balloon.c b/hw/virtio/virtio-balloon.c index a382f43..cc551a3 100644 --- a/hw/virtio/virtio-balloon.c +++ b/hw/virtio/virtio-balloon.c @@ -66,8 +66,7 @@ static const char *balloon_stat_names[] = { */ static inline void reset_stats(VirtIOBalloon *dev) { - int i; - for (i = 0; i < VIRTIO_BALLOON_S_NR; dev->stats[i++] = -1); + dev->stats_cnt = 0; } static bool balloon_stats_supported(const VirtIOBalloon *s) @@ -133,12 +132,20 @@ static void balloon_stats_get_all(Object *obj, Visitor *v, const char *name, if (err) { goto out_end; } - for (i = 0; i < VIRTIO_BALLOON_S_NR; i++) { - visit_type_uint64(v, balloon_stat_names[i], &s->stats[i], &err); + for (i = 0; !err && i < s->stats_cnt; i++) { + if (s->stats[i].tag < VIRTIO_BALLOON_S_NR) { + visit_type_uint64(v, balloon_stat_names[s->stats[i].tag], + &s->stats[i].val, &err); + } else { + gchar *str = g_strdup_printf("x-stat-%04x", s->stats[i].tag); + visit_type_uint64(v, str, &s->stats[i].val, &err); + g_free(str); + } if (err) { break; } } + error_propagate(errp, err); err = NULL; visit_end_struct(v, &err); @@ -273,10 +280,21 @@ static void virtio_balloon_receive_stats(VirtIODevice *vdev, VirtQueue *vq) == sizeof(stat)) { uint16_t tag = virtio_tswap16(vdev, stat.tag); uint64_t val = virtio_tswap64(vdev, stat.val); + int i; offset += sizeof(stat); - if (tag < VIRTIO_BALLOON_S_NR) - s->stats[tag] = val; + for (i = 0; i < s->stats_cnt; i++) { + if (s->stats[i].tag == tag) { + break; + } + } + if (i < ARRAY_SIZE(s->stats)) { + s->stats[i].tag = tag; + s->stats[i].val = val; + if (s->stats_cnt <= i) { + s->stats_cnt = i + 1; + } + } } s->stats_vq_offset = offset; diff --git a/include/hw/virtio/virtio-balloon.h b/include/hw/virtio/virtio-balloon.h index 35f62ac..5c8730e 100644 --- a/include/hw/virtio/virtio-balloon.h +++ b/include/hw/virtio/virtio-balloon.h @@ -36,7 +36,8 @@ typedef struct VirtIOBalloon { VirtQueue *ivq, *dvq, *svq; uint32_t num_pages; uint32_t actual; - uint64_t stats[VIRTIO_BALLOON_S_NR]; + VirtIOBalloonStatModern stats[VIRTIO_BALLOON_S_NR + 32]; + uint16_t stats_cnt; VirtQueueElement *stats_vq_elem; size_t stats_vq_offset; QEMUTimer *stats_timer;