[PATCH v3 09/15] virtio-mem: Better retry handling

David Hildenbrand
2020-05-07T10:33:27Z

Let's start with a retry interval of 5 seconds and double the time until
we reach 5 minutes, in case we keep getting errors. Reset the retry
interval in case we succeeded.

The two main reasons for having to retry are
- The hypervisor is busy and cannot process our request
- We cannot reach the desired requested_size (esp., not enough memory can
get unplugged because we can't allocate any subblocks).

Tested-by: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Oscar Salvador <osalvador@suse.de>
Cc: Michal Hocko <mhocko@kernel.org>
Cc: Igor Mammedov <imammedo@redhat.com>
Cc: Dave Young <dyoung@redhat.com>
Cc: Andrew Morton <akpm@linux-foundation.org>
Cc: Dan Williams <dan.j.williams@intel.com>
Cc: Pavel Tatashin <pasha.tatashin@soleen.com>
Cc: Stefan Hajnoczi <stefanha@redhat.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: David Hildenbrand <david@redhat.com>
---
drivers/virtio/virtio_mem.c | 11 ++++++++---
1 file changed, 8 insertions(+), 3 deletions(-)

diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index a2edb87e5ed8..eb4c16d634e0 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -141,7 +141,9 @@ struct virtio_mem {

/* Timer for retrying to plug/unplug memory. */
struct hrtimer retry_timer;
-#define VIRTIO_MEM_RETRY_TIMER_MS 30000
+ unsigned int retry_timer_ms;
+#define VIRTIO_MEM_RETRY_TIMER_MIN_MS 50000
+#define VIRTIO_MEM_RETRY_TIMER_MAX_MS 300000

/* Memory notifier (online/offline events). */
struct notifier_block memory_notifier;
@@ -1550,6 +1552,7 @@ static void virtio_mem_run_wq(struct work_struct *work)

switch (rc) {
case 0:
+ vm->retry_timer_ms = VIRTIO_MEM_RETRY_TIMER_MIN_MS;
break;
case -ENOSPC:
/*
@@ -1565,8 +1568,7 @@ static void virtio_mem_run_wq(struct work_struct *work)
*/
case -ENOMEM:
/* Out of memory, try again later. */
- hrtimer_start(&vm->retry_timer,
- ms_to_ktime(VIRTIO_MEM_RETRY_TIMER_MS),
+ hrtimer_start(&vm->retry_timer, ms_to_ktime(vm->retry_timer_ms),
HRTIMER_MODE_REL);
break;
case -EAGAIN:
@@ -1586,6 +1588,8 @@ static enum hrtimer_restart virtio_mem_timer_expired(struct hrtimer *timer)
retry_timer);

virtio_mem_retry(vm);
+ vm->retry_timer_ms = min_t(unsigned int, vm->retry_timer_ms * 2,
+ VIRTIO_MEM_RETRY_TIMER_MAX_MS);
return HRTIMER_NORESTART;
}

@@ -1754,6 +1758,7 @@ static int virtio_mem_probe(struct virtio_device *vdev)
spin_lock_init(&vm->removal_lock);
hrtimer_init(&vm->retry_timer, CLOCK_MONOTONIC, HRTIMER_MODE_REL);
vm->retry_timer.function = virtio_mem_timer_expired;
+ vm->retry_timer_ms = VIRTIO_MEM_RETRY_TIMER_MIN_MS;

/* register the virtqueue */
rc = virtio_mem_init_vq(vm);
--
2.25.3