Messages in this thread | | | Date | Tue, 24 Nov 2020 10:38:37 +0100 | From | Borislav Petkov <> | Subject | Re: [PATCH v6] swiotlb: Adjust SWIOTBL bounce buffer size for SEV guests. |
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On Tue, Nov 24, 2020 at 09:25:06AM +0000, Kalra, Ashish wrote: > But what will be the criteria to figure out this percentage? > > As I mentioned earlier, this can be made as complicated as possible by > adding all kind of heuristics but without any predictable performance > gain. > > Or it can be kept simple by using a static percentage value.
Yes, static percentage number based on the guest memory. X% of the guest memory is used for SWIOTLB.
Since you use sev_active(), it means the size computation is done in the guest so that SWIOTLB size is per-guest. Yes?
If so, you can simply take, say, 5% of the guest memory's size and use that for SWIOTLB buffers. Or 6 or X or whatever.
Makes sense?
-- Regards/Gruss, Boris.
https://people.kernel.org/tglx/notes-about-netiquette
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