On Wed, Apr 26, 2017 at 05:09:42PM +0800, Jason Wang wrote: > > > On 2017年04月25日 00:01, Michael S. Tsirkin wrote: > > Applications that consume a batch of entries in one go > > can benefit from ability to return some of them back > > into the ring. > > > > Add an API for that - assuming there's space. If there's no space > > naturally can't do this and have to drop entries, but this implies ring > > is full so we'd likely drop some anyway. > > > > Signed-off-by: Michael S. Tsirkin <m...@redhat.com> > > --- > > > > Jason, if you add this and unconsume the outstanding packets > > on backend disconnect, vhost close and reset, I think > > we should apply your patch even if we don't yet know 100% > > why it helps. > > > > changes from v1: > > - fix up coding style issues reported by Sergei Shtylyov > > > > > > include/linux/ptr_ring.h | 56 > > ++++++++++++++++++++++++++++++++++++++++++++++++ > > 1 file changed, 56 insertions(+) > > > > diff --git a/include/linux/ptr_ring.h b/include/linux/ptr_ring.h > > index 783e7f5..902afc2 100644 > > --- a/include/linux/ptr_ring.h > > +++ b/include/linux/ptr_ring.h > > @@ -457,6 +457,62 @@ static inline int ptr_ring_init(struct ptr_ring *r, > > int size, gfp_t gfp) > > return 0; > > } > > +/* > > + * Return entries into ring. Destroy entries that don't fit. > > + * > > + * Note: this is expected to be a rare slow path operation. > > + * > > + * Note: producer lock is nested within consumer lock, so if you > > + * resize you must make sure all uses nest correctly. > > + * In particular if you consume ring in interrupt or BH context, you must > > + * disable interrupts/BH when doing so. > > + */ > > +static inline void ptr_ring_unconsume(struct ptr_ring *r, void **batch, > > int n, > > + void (*destroy)(void *)) > > +{ > > + unsigned long flags; > > + int head; > > + > > + spin_lock_irqsave(&r->consumer_lock, flags); > > + spin_lock(&r->producer_lock); > > + > > + if (!r->size) > > + goto done; > > + > > + /* > > + * Clean out buffered entries (for simplicity). This way following code > > + * can test entries for NULL and if not assume they are valid. > > + */ > > + head = r->consumer_head - 1; > > + while (likely(head >= r->consumer_tail)) > > + r->queue[head--] = NULL; > > + r->consumer_tail = r->consumer_head; > > + > > + /* > > + * Go over entries in batch, start moving head back and copy entries. > > + * Stop when we run into previously unconsumed entries. > > + */ > > + while (n--) { > > + head = r->consumer_head - 1; > > + if (head < 0) > > + head = r->size - 1; > > + if (r->queue[head]) { > > + /* This batch entry will have to be destroyed. */ > > + ++n; > > + goto done; > > + } > > + r->queue[head] = batch[n]; > > + r->consumer_tail = r->consumer_head = head; > > Looks like something wrong here (bad page state reported), uncomment the > above while() solving the issue. But after staring it for a while I didn't > find anything interesting, maybe you have some idea on this? > > Thanks > > > > + } > > + > > +done: > > + /* Destroy all entries left in the batch. */ > > + while (n--) > > + destroy(batch[n]); > > + spin_unlock(&r->producer_lock); > > + spin_unlock_irqrestore(&r->consumer_lock, flags); > > +} > > + > > static inline void **__ptr_ring_swap_queue(struct ptr_ring *r, void > > **queue, > > int size, gfp_t gfp, > > void (*destroy)(void *))
What's our plan here? I can't delay pull request much longer.