On 8/10/21 7:52 AM, Pavel Begunkov wrote: > For requests with non-fixed files, instead of grabbing just one > reference, we get by the number of left requests, so the following > requests using the same file can take it without atomics. > > However, it's not all win. If there is one request in the middle > not using files or having a fixed file, we'll need to put back the left > references. Even worse if an application submits requests dealing with > different files, it will do a put for each new request, so doubling the > number of atomics needed. Also, even if not used, it's still takes some > cycles in the submission path. > > If a file used many times, it rather makes sense to pre-register it, if > not, we may fall in the described pitfall. So, this optimisation is a > matter of use case. Go with the simpliest code-wise way, remove it. I ran this through the peak testing, not using registered files. Doesn't seem to make a real difference here, at least in the quick testing. Which would seem to indicate we could safely kill it. But that's also the best case for non-registered files, would be curious to see if it makes a real difference now for workloads where the file is being shared. -- Jens Axboe
