missing multichannel crediting patch in Linux client

Steve French smfrench at gmail.com
Thu Oct 6 18:19:28 UTC 2022

Was looking through old patches and noticed one from Aurelien that
looks important but didn't seem to get incorporated into the current
pick_channel code on the client.
It looks like without this patch we could have cases where we assigned
requests to a channel which was out of credits rather than one with
enough credits.
round robin channel allocation is probably fine for many cases except
when other channels have more credits and this channel is short of
credits.  Thoughts?
It might explain some of the perf problems we see with multichannel
not scaling as well as expected on some workloads

"Subject: [PATCH] cifs: try to pick channel with a minimum of credits

Check channel credits to prevent the client from using a starved
channel that cannot send anything.

Special care must be taken in selecting the minimum value: when
channels are created they start off with a small amount that slowly
ramps up as the channel gets used. Thus a new channel might never be
picked if the min value is too big.



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