Wed, Jun 19, 2024 at 09:26:22AM CEST, mst@xxxxxxxxxx wrote:
>On Wed, Jun 19, 2024 at 07:45:16AM +0200, Jiri Pirko wrote:
>> Tue, Jun 18, 2024 at 08:18:12PM CEST, mst@xxxxxxxxxx wrote:
>> >This looks like a sensible way to do this.
>> >Yet something to improve:
>> >
>> >
>> >On Tue, Jun 18, 2024 at 04:44:56PM +0200, Jiri Pirko wrote:
>> >> From: Jiri Pirko <jiri@xxxxxxxxxx>
>> >>
>>
>> [...]
>>
>>
>> >> +static void __free_old_xmit(struct send_queue *sq, struct netdev_queue *txq,
>> >> + bool in_napi, struct virtnet_sq_free_stats *stats)
>> >> {
>> >> unsigned int len;
>> >> void *ptr;
>> >>
>> >> while ((ptr = virtqueue_get_buf(sq->vq, &len)) != NULL) {
>> >> - ++stats->packets;
>> >> -
>> >> if (!is_xdp_frame(ptr)) {
>> >> - struct sk_buff *skb = ptr;
>> >> + struct sk_buff *skb = ptr_to_skb(ptr);
>> >>
>> >> pr_debug("Sent skb %p\n", skb);
>> >>
>> >> - stats->bytes += skb->len;
>> >> + if (is_orphan_skb(ptr)) {
>> >> + stats->packets++;
>> >> + stats->bytes += skb->len;
>> >> + } else {
>> >> + stats->napi_packets++;
>> >> + stats->napi_bytes += skb->len;
>> >> + }
>> >> napi_consume_skb(skb, in_napi);
>> >> } else {
>> >> struct xdp_frame *frame = ptr_to_xdp(ptr);
>> >>
>> >> + stats->packets++;
>> >> stats->bytes += xdp_get_frame_len(frame);
>> >> xdp_return_frame(frame);
>> >> }
>> >> }
>> >> + netdev_tx_completed_queue(txq, stats->napi_packets, stats->napi_bytes);
>> >
>> >Are you sure it's right? You are completing larger and larger
>> >number of bytes and packets each time.
>>
>> Not sure I get you. __free_old_xmit() is always called with stats
>> zeroed. So this is just sum-up of one queue completion run.
>> I don't see how this could become "larger and larger number" as you
>> describe.
>
>Oh. Right of course. Worth a comment maybe? Just to make sure
>we remember not to call __free_old_xmit twice in a row
>without reinitializing stats.
>Or move the initialization into __free_old_xmit to make it
>self-contained ..
Well, the initialization happens in the caller by {0}, Wouldn't
memset in __free_old_xmit() add an extra overhead? IDK.
Perhaps a small comment in __free_old_xmit() would do better.
One way or another, I think this is parallel to this patchset. Will
handle it separatelly if you don't mind.
>WDYT?
>
>>
>> >
>> >For example as won't this eventually trigger this inside dql_completed:
>> >
>> > BUG_ON(count > num_queued - dql->num_completed);
>>
>> Nope, I don't see how we can hit it. Do not complete anything else
>> in addition to what was started in xmit(). Am I missing something?
>>
>>
>> >
>> >?
>> >
>> >
>> >If I am right the perf testing has to be redone with this fixed ...
>> >
>> >
>> >> }
>> >>
>>
>> [...]
>
