[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] Proposed new "memory capacity claim" hypercall/feature
On 08/11/2012 09:47, "Jan Beulich" <JBeulich@xxxxxxxx> wrote: >> Ah, then I am out of date on how Linux services softirqs and preemption? Can >> softirqs/preemption occur any time, even in kernel mode, so long as no locks >> are held? >> >> I thought softirq-type work only happened during event servicing, only if >> the event servicing had interrupted user context (ie, would not happen if >> started from within kernel mode). So the restart of the hypercall trap >> instruction would be an opportunity to service hardirqs, but not softirqs or >> scheduler... > > No, irq_exit() can invoke softirqs, provided this isn't a nested IRQ > (soft as well as hard) or softirqs weren't disabled in the interrupted > context. Ah, okay. In fact maybe that's always been the case and I have misremembered this detail, since condition for softirq entry in Xen has always been more strict than this. > The only thing that indeed is - on non-preemptible kernels - done > only on exit to user mode is the eventual entering of the scheduler. That alone may still be an argument for restricting the batch size from the toolstack? -- Keir _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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