Messages in this thread | | | Date | Wed, 7 Jul 2004 13:04:45 -0400 (EDT) | From | Zwane Mwaikambo <> | Subject | Re: MSI to memory? |
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On Wed, 7 Jul 2004, Helge Hafting wrote:
> Davide Rossetti wrote: > > > Rajesh Shah wrote: > > > >> What type of usage model did you have in mind to have the > >> > >> device write to memory instead of using MSI for interrupts? > >> > >> > > for instance for a fast wake-up trick. the driver loops on a memory > > location until the MSI write access changes the memory content... > > Won't that put a bad load on the bus? Someone else might need it: > * Another cpu in a smp system > * Any device doing bus-master transfers, even in a UP system > > That polling loop had better be guaranteed to be _very_ short.
mwait/monitor is best suited for such things and doesn't result in pounding on memory. Considering the box has MSI, there is a higher possibility of it also having the mwait/monitor instructions.
Zwane
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