On 2024/4/4 19:27, Niklas Schnelle wrote:
On Thu, 2024-04-04 at 18:20 +0800, Wen Gu wrote:
On 2024/4/4 01:20, Gerd Bayer wrote:
On Sun, 2024-03-24 at 21:55 +0800, Wen Gu wrote:
When I instrumented this to see, why I still see tons of my other
temporary instrumentation messages from the "ism" driver, I found that
in my setup loopback-ism is used rather infrequently.
I suspect this is due to how the SMC proposals are constructed in
net/smc/af_smc.c and net/smc/smc_pnet.c - and later evaluated in
smc_check_ism_v2_match() - where there is a first-come-first-serve
selection.
I wonder if one should change that to favour loopback-ism over "real"
ISM devices - and how this could be achieved elegantly.
Just some food for thought... Probably little you can do on x86.
Yes, it is about the priority of available ISM devices, and now it
is decided by their order in the smcd_dev_list. The later registered
ISMv2 devices(without pnetid) will be added to the beginning of the
list (see smcd_register_dev()). So there is a probability that
loopback-ism will not be ranked first, since it is added into list
earlier during smc_init().
If we have the runtime switch of loopback-ism, we can re-active the
loopback-ism, that make it be re-added into the beginning of the dev
list and be chosen first. Or a new netlink command to adjust the slot
order of available ISM devices in the list. As we discussed before,
that could be tasks in stage 1 or stage 2.
Thanks!
Maybe when adding the ISM devices we could instead make sure that all
ISM devices are added after loopback and loopback is added in the
beginning. I think loopback should always be preferred and would
consider it a bug if it isn't faster too. Between virtio-ism and ISM it
may be less clear so maybe for stage 2 we would want a priority setting
and then insert ordered by priority. Thoughts?
I have no objection. If we all agree, I will keep it at the beginning of the list.
Thanks!
