[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH 1/2] IRQ: allocate CPU masks dynamically
>>> On 03.11.11 at 16:43, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote: > On 03/11/11 15:17, Jan Beulich wrote: >>>>> On 03.11.11 at 15:49, Andrew Cooper <andrew.cooper3@xxxxxxxxxx> wrote: >>> On 03/11/11 14:26, Jan Beulich wrote: >>>> IRQ: allocate CPU masks dynamically >>>> >>>> This includes delaying the initialization of dynamically created IRQs >>>> until their actual first use and some further elimination of uses of >>>> struct irq_cfg. >>>> >>>> Signed-off-by: Jan Beulich <jbeulich@xxxxxxxx> >>> Acked-by: Andrew Cooper <andrew.cooper3@xxxxxxxxxx> >>> >>> One query which may or may not affect the patch. Would we get better >>> caching characteristics if all cpumasks were allocated in consecutive >>> memory, rather than having 3 individual allocs in arch_init_one_irq_desc ? >> That was what the first version of the patch did, rejected by Keir >> (and not liked too much by me either). >> >> Jan > > My understanding of the objection was hiding the variables themselves as > an array in the code. > > An alternative approach such as alloc'ing 3*sizeof(cpu mask) (cache > aligned) and assigning the relevant pointers to the current > cpumask_var_t's would be a suitable approach which causes the cpumasks > to be in contiguous memory, but not changing how they are referenced in > the code. That would mean just open-coding what the former patch did by abstraction. In my opinion that is even worse - either we want a generally usable mechanism to do this, or we don't do it at all. Jan _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxxxxxxxx http://lists.xensource.com/xen-devel
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