Question about sendzc notif CQE ordering

[bnbajwa]

Hello,

Consider the following sequence:

1. submit sendzc SQE for buf1
2. wait for 1st sendzc CQE
3. submit sendzc SQE for buf2
4. wait for 1st sendzc CQE

At this point, I expect 2 notif CQEs for each of the two bufs.

My question: is there any ordering guaranteed for the notif CQEs? i.e. is the following sequence guaranteed?:

1. notif CQE for buf1
2. notif CQE for buf2

i.e. could notif CQE for buf2 arrive BEFORE notif CQE for buf1?

Many Thanks

[axboe]

CC @isilence

[redbaron]

If you have both buffers ready to be sent, then submit them linked or use single vector write

[isilence]

@bnbajwa, there is no ordering guarantee for zc notification CQEs.

If you have both buffers ready to be sent, then submit them linked or use single vector write

And it wouldn't change it for notifications, because there is no ordering b/w notification and linked requests.
E.g. with sendzc -> nop you can likely a completion ordering as this: sendzc - nop - notif

[isilence]

But it's likely to be ordered, so it can still be used as an optimisation if you handle corner cases in the userspace.