Hi Ming, Having no [PATCH 1/2] blk-mq: add blk_mq_max_nr_hw_queues() in inbox. So I reply here. At first glance, I think that the cpu hot plug callback hook should be the remedy for the newly introduced blk_mq_max_nr_hw_queues(), although it is more complicated. Consider the scene where nr_cpus=4, which can speed up the dumping process, the blk_mq_max_nr_hw_queues() can not utilize the other three cpus. Thanks, Pingfan On Mon, Jul 10, 2023 at 5:16 PM Ming Lei <ming.lei@xxxxxxxxxx> wrote: > > On Mon, Jul 10, 2023 at 08:41:09AM +0200, Christoph Hellwig wrote: > > On Sat, Jul 08, 2023 at 10:02:59AM +0800, Ming Lei wrote: > > > Take blk-mq's knowledge into account for calculating io queues. > > > > > > Fix wrong queue mapping in case of kdump kernel. > > > > > > On arm and ppc64, 'maxcpus=1' is passed to kdump command line, see > > > `Documentation/admin-guide/kdump/kdump.rst`, so num_possible_cpus() > > > still returns all CPUs. > > > > That's simply broken. Please fix the arch code to make sure > > it does not return a bogus num_possible_cpus value for these > > That is documented in Documentation/admin-guide/kdump/kdump.rst. > > On arm and ppc64, 'maxcpus=1' is passed for kdump kernel, and "maxcpu=1" > simply keep one of CPU cores as online, and others as offline. > > So Cc our arch(arm & ppc64) & kdump guys wrt. passing 'maxcpus=1' for > kdump kernel. > > > setups, otherwise you'll have to paper over it in all kind of > > drivers. > > The issue is only triggered for drivers which use managed irq & > multiple hw queues. > > > Thanks, > Ming > > > _______________________________________________ > kexec mailing list > kexec@xxxxxxxxxxxxxxxxxxx > http://lists.infradead.org/mailman/listinfo/kexec >
