Le lundi 31 mai 2010 à 18:04 +0200, Andi Kleen a écrit : > DM-CRYPT: Scale to multiple CPUs > > Currently dm-crypt does all encryption work per dmcrypt mapping in a > single workqueue. This does not scale well when multiple CPUs > are submitting IO at a high rate. The single CPU running the single > thread cannot keep up with the encryption and encrypted IO performance > tanks. > > This patch changes the crypto workqueue to be per CPU. This means > that as long as the IO submitter (or the interrupt target CPUs > for reads) runs on different CPUs the encryption work will be also > parallel. > > To avoid a bottleneck on the IO worker I also changed those to be > per CPU threads. > > There is still some shared data, so I suspect some bouncing > cache lines. But I haven't done a detailed study on that yet. > > All the threads are global, not per CPU. That is to avoid a thread > explosion on systems with a large number of CPUs and a larger > number of dm-crypt mappings. The code takes care to avoid problems > with nested mappings. > > Signed-off-by: Andi Kleen <ak@xxxxxxxxxxxxxxx> > /* > + * Duplicated per cpu state. Access through > + * per_cpu_ptr() only. > + */ > + struct crypt_cpu *cpu; > + > + /* > * Layout of each crypto request: > * Since commit e0fdb0e050eae331, we have a __percpu annotation so that sparse can be augmented. This would also make the comment unnecessary... We also have this_cpu_ accessors > + return per_cpu_ptr(cc->cpu, smp_processor_id()); this_cpu_ptr(cc->cpu) and __thic_cpu_ptr() for the 'raw' version > + __get_cpu_var(io_wq_cpu) = current; this_cpu_write(io_wq_cpu, current) -- dm-devel mailing list dm-devel@xxxxxxxxxx https://www.redhat.com/mailman/listinfo/dm-devel
