[dpdk-dev] [PATCH v2 2/3] vhost: move dirty logging cache out of the virtqueue
Maxime Coquelin
maxime.coquelin at redhat.com
Wed Mar 17 11:20:45 CET 2021
On 3/16/21 2:13 PM, David Marchand wrote:
> On Tue, Mar 16, 2021 at 1:42 PM Maxime Coquelin
> <maxime.coquelin at redhat.com> wrote:
>>
>> This patch moves the per-virtqueue's dirty logging cache
>> out of the virtqueue struct, by allocating it dynamically
>> only when live-migration is enabled.
>>
>> It saves 8 cachelines in vhost_virtqueue struct.
>>
>> Signed-off-by: Maxime Coquelin <maxime.coquelin at redhat.com>
>> ---
>> lib/librte_vhost/vhost.c | 14 ++++++++++++++
>> lib/librte_vhost/vhost.h | 2 +-
>> lib/librte_vhost/vhost_user.c | 25 +++++++++++++++++++++++++
>> 3 files changed, 40 insertions(+), 1 deletion(-)
>>
>> diff --git a/lib/librte_vhost/vhost.c b/lib/librte_vhost/vhost.c
>> index 5a7c0c6cff..c3490ce897 100644
>> --- a/lib/librte_vhost/vhost.c
>> +++ b/lib/librte_vhost/vhost.c
>> @@ -145,6 +145,10 @@ __vhost_log_cache_sync(struct virtio_net *dev, struct vhost_virtqueue *vq)
>> if (unlikely(!dev->log_base))
>> return;
>>
>> + /* No cache, nothing to sync */
>> + if (unlikely(!vq->log_cache))
>> + return;
>> +
>> rte_atomic_thread_fence(__ATOMIC_RELEASE);
>>
>> log_base = (unsigned long *)(uintptr_t)dev->log_base;
>> @@ -177,6 +181,14 @@ vhost_log_cache_page(struct virtio_net *dev, struct vhost_virtqueue *vq,
>> uint32_t offset = page / (sizeof(unsigned long) << 3);
>> int i;
>>
>> + if (unlikely(!vq->log_cache)) {
>> + /* No logging cache allocated, write dirty log map directly */
>> + rte_smp_wmb();
>
> We try not to reintroduce full barriers (checkpatch caught this).
Agree, the rebase introduced it again silently.
>
>> + vhost_log_page((uint8_t *)(uintptr_t)dev->log_base, page);
>> +
>> + return;
>> + }
>> +
>> for (i = 0; i < vq->log_cache_nb_elem; i++) {
>> struct log_cache_entry *elem = vq->log_cache + i;
>>
>> @@ -354,6 +366,8 @@ free_vq(struct virtio_net *dev, struct vhost_virtqueue *vq)
>> }
>> rte_free(vq->batch_copy_elems);
>> rte_mempool_free(vq->iotlb_pool);
>> + if (vq->log_cache)
>> + rte_free(vq->log_cache);
>
> No if() needed.
Yes, will fix in next revision.
>
>> rte_free(vq);
>> }
>>
>> diff --git a/lib/librte_vhost/vhost.h b/lib/librte_vhost/vhost.h
>> index 717f410548..3a71dfeed9 100644
>> --- a/lib/librte_vhost/vhost.h
>> +++ b/lib/librte_vhost/vhost.h
>> @@ -183,7 +183,7 @@ struct vhost_virtqueue {
>> bool used_wrap_counter;
>> bool avail_wrap_counter;
>>
>> - struct log_cache_entry log_cache[VHOST_LOG_CACHE_NR];
>> + struct log_cache_entry *log_cache;
>> uint16_t log_cache_nb_elem;
>>
>> rte_rwlock_t iotlb_lock;
>> diff --git a/lib/librte_vhost/vhost_user.c b/lib/librte_vhost/vhost_user.c
>> index a60bb945ad..0f452d6ff3 100644
>> --- a/lib/librte_vhost/vhost_user.c
>> +++ b/lib/librte_vhost/vhost_user.c
>> @@ -2022,6 +2022,11 @@ vhost_user_get_vring_base(struct virtio_net **pdev,
>> rte_free(vq->batch_copy_elems);
>> vq->batch_copy_elems = NULL;
>>
>> + if (vq->log_cache) {
>> + rte_free(vq->log_cache);
>> + vq->log_cache = NULL;
>> + }
>
> Idem.
>
>
Thanks,
Maxime
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