Messages in this thread | | | Date | Wed, 26 Nov 2008 16:03:59 -0800 | From | "H. Peter Anvin" <> | Subject | Re: [Lguest] [PATCH RFC/RFB] x86_64, i386: interrupt dispatch changes |
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Avi Kivity wrote: > >> Here is a prototype patch of the compressed IRQ stubs -- this patch >> compresses them down to 7 stubs per 32-byte cache line (or part of cache >> line) at the expense of a back-to-back jmp which has the potential of >> being ugly on some pipelines (we can only get 4 stubs into 32 bytes >> without that). > > You could actually get 4-byte stubs, using a 16-bit call (66 e8 ww ww). > But it would be slower, since we won't be pairing it with a ret. >
Yes, I would consider that a theoretical exercise only :)
> I suspect we could get it down to three bytes, by sharing the last byte > of the four-byte call sequence with the first byte of the next: > > 66 e8 ff 66 e8 fc 66 e8 f9 66 e8 f6 ... > > Every three bytes a new stub begins; it's a four-byte call to offset > 0x6703 relative to the beginning of the first stub. > > Can anyone better 24 bits/stub?
On the entirely silly level...
CC xx
-hpa
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