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powerpc/pseries: lparcfg calculate PURR on demand

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For SPLPAR, lparcfg provides a sum of PURR registers for all CPUs.
Currently this is done by reading PURR in context switch and timer
interrupt, and storing that into a per-CPU variable. These are summed
to provide the value.

This does not work with all timer schemes (e.g., NO_HZ_FULL), and it
is sub-optimal for performance because it reads the PURR register on
every context switch, although that's been difficult to distinguish
from noise in the contxt_switch microbenchmark.

This patch implements the sum by calling a function on each CPU, to
read and add PURR values of each CPU.

Signed-off-by: Nicholas Piggin <npiggin@gmail.com>
Signed-off-by: Michael Ellerman <mpe@ellerman.id.au>
This commit is contained in:
Nicholas Piggin
2018-05-05 03:19:30 +10:00
committed by Michael Ellerman
parent 36d632ea83
commit 3d3a6021dd
4 changed files with 10 additions and 38 deletions
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8
arch/powerpc/include/asm/time.h
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@@ -196,14 +196,6 @@ extern u64 mulhdu(u64, u64);
extern void div128_by_32(u64 dividend_high, u64 dividend_low,
unsigned divisor, struct div_result *dr);
/* Used to store Processor Utilization register (purr) values */
struct cpu_usage {
u64 current_tb; /* Holds the current purr register values */
};
DECLARE_PER_CPU(struct cpu_usage, cpu_usage_array);
extern void secondary_cpu_time_init(void);
extern void __init time_init(void);