[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCHv2 5/5] evtchn: pad struct evtchn to 64 bytes
On 16/06/15 13:57, Julien Grall wrote: > On 16/06/15 12:59, Jan Beulich wrote: >>>>> On 16.06.15 at 13:14, <julien.grall@xxxxxxxxxx> wrote: >>> On 15/06/2015 16:48, David Vrabel wrote: >>>> diff --git a/xen/include/xen/sched.h b/xen/include/xen/sched.h >>>> index 44ea92d..a0ff9d2 100644 >>>> --- a/xen/include/xen/sched.h >>>> +++ b/xen/include/xen/sched.h >>>> @@ -129,7 +129,7 @@ struct evtchn >>>> #endif >>>> } ssid; >>>> #endif >>>> -}; >>>> +} __attribute__((aligned(64))); >>> >>> Why don't you use __cacheline_aligned? >> >> That would double the size on x86, for little or no benefit. > > Well, the cache line size is not necessarily 64 bytes on every > architecture. In the case of ARM, the cache line depends on the > processor version. > > __cacheline_aligned is the only way to ensure that the cache line is not > shared on ARM. > > AFAIU, the goal of this patch is to avoid sharing the cache line. If > not, the commit message is misleading because it claims that a cache > line is always 64 bytes... We want to avoid sharing the cache line where we can do so for no additional memory cost. David _______________________________________________ Xen-devel mailing list Xen-devel@xxxxxxxxxxxxx http://lists.xen.org/xen-devel
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