Messages in this thread |  | | Subject | Re: [PATCH RFC v2] ptr_ring: add ptr_ring_unconsume | From | Jason Wang <> | Date | Wed, 10 May 2017 10:01:23 +0800 |
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On 2017年05月09日 21:26, Michael S. Tsirkin wrote: > 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 <mst@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. >
I'm waiting for net-next to be opened (since the series touches tun/tap).
Let me post a new version soon.
Thanks
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