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>

1 files changed, 34 insertions, 2 deletions

diff --git a/arch/alpha/Kconfig b/arch/alpha/Kconfig
index 51cc8c353164..a67b971c830a 100644
--- a/arch/alpha/Kconfig
+++ b/arch/alpha/Kconfig
@@ -627,9 +627,41 @@ config VERBOSE_MCHECK_ON
 
           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"