lpfc: Mitigate high memory pre-allocation by SCSI-MQ
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Quoted 6 lines · James Smart
Quoted 3 lines · Ming Lei
I am wondering why you use 2 *
num_possible_nodes()as the limit instead ofnum_possible_nodes(), could you explain it a bit?
Quoted 6 lines
The number comes from most systems being dual socket systems, thus a numa node count of 2. Some of these dual socket systems can be high cpu counts per socket. We did see a difference, on different architectures and where cpu counts were high per socket, that more hwqs per socket did help. So if there can be more than 1 hwq per socket then I think that is goodness.
I guess it isn't related with CPU cores per socket, what matters is number of sockets, given each CPU core in same socket is in same position wrt. RW preformance on same shared memory, so looks the following way is what we need:
shost->nr_hw_queues = max_t(int, num_possible_nodes(),
nr_processor_sockets);
However, I don't know how to retrieve 'nr_processor_sockets' in kernel. Maybe topology_max_packages() can be used for x86, not see how to read it for other ARCHs.
Cc Thomas and linux-kernel list.
Thanks,
Ming Lei