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Re: [PATCH 12/12] xen/x86: add hypercall performance counters for hvm, correct pv
- To: Juergen Gross <jgross@xxxxxxxx>
- From: Jan Beulich <jbeulich@xxxxxxxx>
- Date: Thu, 21 Oct 2021 17:19:41 +0200
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- Cc: Andrew Cooper <andrew.cooper3@xxxxxxxxxx>, Roger Pau Monné <roger.pau@xxxxxxxxxx>, Wei Liu <wl@xxxxxxx>, xen-devel@xxxxxxxxxxxxxxxxxxxx
- Delivery-date: Thu, 21 Oct 2021 15:20:02 +0000
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On 15.10.2021 14:51, Juergen Gross wrote:
> The HVM hypercall handler is missing incrementing the per hypercall
> counters. Add that.
>
> The counters for PV are handled wrong, as they are not using
> perf_incra() with the number of the hypercall as index, but are
> incrementing the total number of hypercalls only. Fix that.
Why do you say "total number"? Isn't it that all accounting goes into
set_trap_table's slot, effectively making that slot a "total number"
despite not being labeled that way?
Also this fix renders largely redundant the calls_to_multicall counter.
Could I talk you into deleting that at the same time? (As to the "not
fully redundant": I consider it suspicious that this counter gets
incremented at the bottom of the function, not at the top.)
Finally I take it that with the Kconfig setting being under DEBUG, we
don't consider security supported builds with PERF_COUNTERS enabled.
Otherwise as a prereq I would think perfc_incra() would need teaching
of array_index_nospec().
In any event, preferably with at least the description slightly
adjusted,
Reviewed-by: Jan Beulich <jbeulich@xxxxxxxx>
Jan
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