[PATCH] HZ: 300Hz support

Fix two things.  Firstly the unit is "Hz" not "HZ".  Secondly it is useful
to have 300Hz support when doing multimedia work.  250 is fine for us in
Europe but the US frame rate is 30fps (29.99 blah for pedants).  300 gives
us a tick divisible by both 25 and 30, and for interlace work 50 and 60.
It's also giving similar performance to 250Hz.

I'd argue we should remove 250 and add 300, but that might be excess
disruption for now.

Signed-off-by: Alan Cox <alan@redhat.com>
Signed-off-by: Andrew Morton <akpm@osdl.org>
Signed-off-by: Linus Torvalds <torvalds@osdl.org>

1 files changed, 15 insertions, 5 deletions

diff --git a/kernel/Kconfig.hz b/kernel/Kconfig.hz
index 248e1c396f8b..4af15802ccd4 100644
--- a/kernel/Kconfig.hz
+++ b/kernel/Kconfig.hz
@@ -7,7 +7,7 @@ choice
         default HZ_250
         help
          Allows the configuration of the timer frequency. It is customary
-         to have the timer interrupt run at 1000 HZ but 100 HZ may be more
+         to have the timer interrupt run at 1000 Hz but 100 Hz may be more
          beneficial for servers and NUMA systems that do not need to have
          a fast response for user interaction and that may experience bus
          contention and cacheline bounces as a result of timer interrupts.
@@ -19,21 +19,30 @@ choice
         config HZ_100
                 bool "100 HZ"
         help
-          100 HZ is a typical choice for servers, SMP and NUMA systems
+          100 Hz is a typical choice for servers, SMP and NUMA systems
           with lots of processors that may show reduced performance if
           too many timer interrupts are occurring.
 
         config HZ_250
                 bool "250 HZ"
         help
-         250 HZ is a good compromise choice allowing server performance
+         250 Hz is a good compromise choice allowing server performance
          while also showing good interactive responsiveness even
-         on SMP and NUMA systems.
+         on SMP and NUMA systems. If you are going to be using NTSC video
+         or multimedia, selected 300Hz instead.
+
+        config HZ_300
+                bool "300 HZ"
+        help
+         300 Hz is a good compromise choice allowing server performance
+         while also showing good interactive responsiveness even
+         on SMP and NUMA systems and exactly dividing by both PAL and
+         NTSC frame rates for video and multimedia work.
 
         config HZ_1000
                 bool "1000 HZ"
         help
-         1000 HZ is the preferred choice for desktop systems and other
+         1000 Hz is the preferred choice for desktop systems and other
          systems requiring fast interactive responses to events.
 
 endchoice
@@ -42,5 +51,6 @@ config HZ
         int
         default 100 if HZ_100
         default 250 if HZ_250
+        default 300 if HZ_300
         default 1000 if HZ_1000