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virtio-mem: generalize handling when memory is getting onlined deferred

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We don't want to add too much memory when it's not getting onlined
immediately, to avoid running OOM. Generalize the handling, to avoid
making use of memory block states. Use a threshold of 1 GiB for now.

Properly adjust the offline size when adding/removing memory. As we are
not always protected by a lock when touching the offline size, use an
atomic64_t. We don't care about races (e.g., someone offlining memory
while we are adding more), only about consistent values.

(1 GiB needs a memmap of ~16MiB - which sounds reasonable even for
 setups with little boot memory and (possibly) one virtio-mem device per
 node)

We don't want to retrigger when onlining is caused immediately by our
action (e.g., adding memory which immediately gets onlined), so use a
flag to indicate if the workqueue is active and use that as an
indicator whether to trigger a retry. This will also be especially relevant
for Big Block Mode (BBM), whereby we might re-online memory in case
offlining of another memory block failed.

Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: David Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20201112133815.13332-17-david@redhat.com
Signed-off-by: Michael S. Tsirkin <mst@redhat.com>
This commit is contained in:
David Hildenbrand 2020-11-12 14:38:02 +01:00 committed by Michael S. Tsirkin
parent 1d33c2caa8
commit 98ff9f9411
1 changed files with 63 additions and 32 deletions
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95
drivers/virtio/virtio_mem.c
View File

@ -51,6 +51,7 @@ struct virtio_mem {
/* Workqueue that processes the plug/unplug requests. */
struct work_struct wq;
atomic_t wq_active;
atomic_t config_changed;
/* Virtqueue for guest->host requests. */
@ -99,7 +100,15 @@ struct virtio_mem {
/* Summary of all memory block states. */
unsigned long nb_mb_state[VIRTIO_MEM_MB_STATE_COUNT];
#define VIRTIO_MEM_NB_OFFLINE_THRESHOLD 10
/*
* We don't want to add too much memory if it's not getting onlined,
* to avoid running OOM. Besides this threshold, we allow to have at
* least two offline blocks at a time (whatever is bigger).
*/
#define VIRTIO_MEM_DEFAULT_OFFLINE_THRESHOLD (1024 * 1024 * 1024)
atomic64_t offline_size;
uint64_t offline_threshold;
/*
* One byte state per memory block.
@ -405,6 +414,18 @@ static int virtio_mem_sb_bitmap_prepare_next_mb(struct virtio_mem *vm)
return 0;
}
/*
* Test if we could add memory without creating too much offline memory -
* to avoid running OOM if memory is getting onlined deferred.
*/
static bool virtio_mem_could_add_memory(struct virtio_mem *vm, uint64_t size)
{
if (WARN_ON_ONCE(size > vm->offline_threshold))
return false;
return atomic64_read(&vm->offline_size) + size <= vm->offline_threshold;
}
/*
* Try to add a memory block to Linux. This will usually only fail
* if out of memory.
@ -417,6 +438,8 @@ static int virtio_mem_sb_bitmap_prepare_next_mb(struct virtio_mem *vm)
static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id)
{
const uint64_t addr = virtio_mem_mb_id_to_phys(mb_id);
const uint64_t size = memory_block_size_bytes();
int rc;
/*
* When force-unloading the driver and we still have memory added to
@ -430,10 +453,13 @@ static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id)
}
dev_dbg(&vm->vdev->dev, "adding memory block: %lu\n", mb_id);
return add_memory_driver_managed(vm->nid, addr,
memory_block_size_bytes(),
vm->resource_name,
MEMHP_MERGE_RESOURCE);
/* Memory might get onlined immediately. */
atomic64_add(size, &vm->offline_size);
rc = add_memory_driver_managed(vm->nid, addr, size, vm->resource_name,
MEMHP_MERGE_RESOURCE);
if (rc)
atomic64_sub(size, &vm->offline_size);
return rc;
}
/*
@ -448,16 +474,19 @@ static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id)
static int virtio_mem_mb_remove(struct virtio_mem *vm, unsigned long mb_id)
{
const uint64_t addr = virtio_mem_mb_id_to_phys(mb_id);
const uint64_t size = memory_block_size_bytes();
int rc;
dev_dbg(&vm->vdev->dev, "removing memory block: %lu\n", mb_id);
rc = remove_memory(vm->nid, addr, memory_block_size_bytes());
if (!rc)
rc = remove_memory(vm->nid, addr, size);
if (!rc) {
atomic64_sub(size, &vm->offline_size);
/*
* We might have freed up memory we can now unplug, retry
* immediately instead of waiting.
*/
virtio_mem_retry(vm);
}
return rc;
}
@ -473,18 +502,20 @@ static int virtio_mem_mb_offline_and_remove(struct virtio_mem *vm,
unsigned long mb_id)
{
const uint64_t addr = virtio_mem_mb_id_to_phys(mb_id);
const uint64_t size = memory_block_size_bytes();
int rc;
dev_dbg(&vm->vdev->dev, "offlining and removing memory block: %lu\n",
mb_id);
rc = offline_and_remove_memory(vm->nid, addr,
memory_block_size_bytes());
if (!rc)
rc = offline_and_remove_memory(vm->nid, addr, size);
if (!rc) {
atomic64_sub(size, &vm->offline_size);
/*
* We might have freed up memory we can now unplug, retry
* immediately instead of waiting.
*/
virtio_mem_retry(vm);
}
return rc;
}
@ -567,8 +598,6 @@ static void virtio_mem_notify_offline(struct virtio_mem *vm,
static void virtio_mem_notify_online(struct virtio_mem *vm, unsigned long mb_id)
{
unsigned long nb_offline;
switch (virtio_mem_mb_get_state(vm, mb_id)) {
case VIRTIO_MEM_MB_STATE_OFFLINE_PARTIAL:
virtio_mem_mb_set_state(vm, mb_id,
@ -581,12 +610,6 @@ static void virtio_mem_notify_online(struct virtio_mem *vm, unsigned long mb_id)
BUG();
break;
}
nb_offline = vm->nb_mb_state[VIRTIO_MEM_MB_STATE_OFFLINE] +
vm->nb_mb_state[VIRTIO_MEM_MB_STATE_OFFLINE_PARTIAL];
/* see if we can add new blocks now that we onlined one block */
if (nb_offline == VIRTIO_MEM_NB_OFFLINE_THRESHOLD - 1)
virtio_mem_retry(vm);
}
static void virtio_mem_notify_going_offline(struct virtio_mem *vm,
@ -681,6 +704,7 @@ static int virtio_mem_memory_notifier_cb(struct notifier_block *nb,
case MEM_OFFLINE:
virtio_mem_notify_offline(vm, mb_id);
atomic64_add(size, &vm->offline_size);
/*
* Trigger the workqueue. Now that we have some offline memory,
* maybe we can handle pending unplug requests.
@ -693,6 +717,18 @@ static int virtio_mem_memory_notifier_cb(struct notifier_block *nb,
break;
case MEM_ONLINE:
virtio_mem_notify_online(vm, mb_id);
atomic64_sub(size, &vm->offline_size);
/*
* Start adding more memory once we onlined half of our
* threshold. Don't trigger if it's possibly due to our actipn
* (e.g., us adding memory which gets onlined immediately from
* the core).
*/
if (!atomic_read(&vm->wq_active) &&
virtio_mem_could_add_memory(vm, vm->offline_threshold / 2))
virtio_mem_retry(vm);
vm->hotplug_active = false;
mutex_unlock(&vm->hotplug_mutex);
break;
@ -1151,18 +1187,6 @@ static int virtio_mem_prepare_next_mb(struct virtio_mem *vm,
return 0;
}
/*
* Don't add too many blocks that are not onlined yet to avoid running OOM.
*/
static bool virtio_mem_too_many_mb_offline(struct virtio_mem *vm)
{
unsigned long nb_offline;
nb_offline = vm->nb_mb_state[VIRTIO_MEM_MB_STATE_OFFLINE] +
vm->nb_mb_state[VIRTIO_MEM_MB_STATE_OFFLINE_PARTIAL];
return nb_offline >= VIRTIO_MEM_NB_OFFLINE_THRESHOLD;
}
/*
* Try to plug the desired number of subblocks and add the memory block
* to Linux.
@ -1316,7 +1340,7 @@ static int virtio_mem_plug_request(struct virtio_mem *vm, uint64_t diff)
/* Try to plug and add unused blocks */
virtio_mem_for_each_mb_state(vm, mb_id, VIRTIO_MEM_MB_STATE_UNUSED) {
if (virtio_mem_too_many_mb_offline(vm))
if (!virtio_mem_could_add_memory(vm, memory_block_size_bytes()))
return -ENOSPC;
rc = virtio_mem_mb_plug_and_add(vm, mb_id, &nb_sb);
@ -1327,7 +1351,7 @@ static int virtio_mem_plug_request(struct virtio_mem *vm, uint64_t diff)
/* Try to prepare, plug and add new blocks */
while (nb_sb) {
if (virtio_mem_too_many_mb_offline(vm))
if (!virtio_mem_could_add_memory(vm, memory_block_size_bytes()))
return -ENOSPC;
rc = virtio_mem_prepare_next_mb(vm, &mb_id);
@ -1620,6 +1644,7 @@ static void virtio_mem_run_wq(struct work_struct *work)
if (vm->broken)
return;
atomic_set(&vm->wq_active, 1);
retry:
rc = 0;
@ -1680,6 +1705,8 @@ retry:
"unknown error, marking device broken: %d\n", rc);
vm->broken = true;
}
atomic_set(&vm->wq_active, 0);
}
static enum hrtimer_restart virtio_mem_timer_expired(struct hrtimer *timer)
@ -1788,6 +1815,10 @@ static int virtio_mem_init(struct virtio_mem *vm)
memory_block_size_bytes());
vm->next_mb_id = vm->first_mb_id;
/* Prepare the offline threshold - make sure we can add two blocks. */
vm->offline_threshold = max_t(uint64_t, 2 * memory_block_size_bytes(),
VIRTIO_MEM_DEFAULT_OFFLINE_THRESHOLD);
dev_info(&vm->vdev->dev, "start address: 0x%llx", vm->addr);
dev_info(&vm->vdev->dev, "region size: 0x%llx", vm->region_size);
dev_info(&vm->vdev->dev, "device block size: 0x%llx",