alpha: Allow HZ to be configured
With the 1024Hz default, we spend 50% of QEMU emulation
processing timer interrupts.
Signed-off-by: Richard Henderson <rth@twiddle.net>
diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 51cc8c3..a67b971 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -627,9 +627,41 @@
Take the default (1) unless you want more control or more info.
+choice
+ prompt "Timer interrupt frequency (HZ)?"
+ default HZ_128 if ALPHA_QEMU
+ default HZ_1200 if ALPHA_RAWHIDE
+ default HZ_1024
+ ---help---
+ The frequency at which timer interrupts occur. A high frequency
+ minimizes latency, whereas a low frequency minimizes overhead of
+ process accounting. The later effect is especially significant
+ when being run under QEMU.
+
+ Note that some Alpha hardware cannot change the interrupt frequency
+ of the timer. If unsure, say 1024 (or 1200 for Rawhide).
+
+ config HZ_32
+ bool "32 Hz"
+ config HZ_64
+ bool "64 Hz"
+ config HZ_128
+ bool "128 Hz"
+ config HZ_256
+ bool "256 Hz"
+ config HZ_1024
+ bool "1024 Hz"
+ config HZ_1200
+ bool "1200 Hz"
+endchoice
+
config HZ
- int
- default 1200 if ALPHA_RAWHIDE
+ int
+ default 32 if HZ_32
+ default 64 if HZ_64
+ default 128 if HZ_128
+ default 256 if HZ_256
+ default 1200 if HZ_1200
default 1024
source "drivers/pci/Kconfig"