Re: [dpdk-dev] Missing an increment on vq->log_cache_nb_elem ?

[Ilya Maximets <i.maximets@samsung.com>]

> Hi, 
> 
> 
> In the latest dpdk master branch, in the function *vhost_log_cache_page*:
> 
> 
> static __rte_always_inline void
> vhost_log_cache_page(struct virtio_net *dev, struct vhost_virtqueue *vq,
> 			uint64_t page)
> {
> 	uint32_t bit_nr = page % (sizeof(unsigned long) << 3);
> 	uint32_t offset = page / (sizeof(unsigned long) << 3);
> 	int i;
> 
> 	for (i = 0; i < vq->log_cache_nb_elem; i++) {
> 		struct log_cache_entry *elem = vq->log_cache + i;
> 
> 		if (elem->offset == offset) {
> 			elem->val |= (1UL << bit_nr);
> 			return;
> 		}
> 	}
> 
> 	if (unlikely(i >= VHOST_LOG_CACHE_NR)) {
> 		/*
> 		 * No more room for a new log cache entry,
> 		 * so write the dirty log map directly.
> 		 */
> 		rte_smp_wmb();
> 		vhost_log_page((uint8_t *)(uintptr_t)dev->log_base, page);
> 
> 		return;
> 	}
> 
> 	vq->log_cache[i].offset = offset;
> 	vq->log_cache[i].val = (1UL << bit_nr);
> }
> 
> Did it just miss an increment on vq->log_cache_nb_elem ?

Hi. Thanks for pointing that.

I looked through the code and I see no updates of 'vq->log_cache_nb_elem'.
Looks like it always equal to initial zero value.

Maxime, I'm afraid that this means that currently pages logging is not
performed at all. Could you please check?

Best regards, Ilya Maximets.