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Subjectsetting CONFIG_HZ=2000 screws up ntpd
Dear list,
I use attached patch to speed up HZ from 1000 to 2000. I use this hack
starting from kernel 2.6.7 and I have not experienced any particular
problems. Recently I've started to use NTP and have noticed that ntp
client loose synchronization, if this patch is applied, i.e. it
connects, synchronizes, and then after a few polls, jitter just jumps
to 5 digit number. I've rechecked the behavior on the kernel 2.6.11
and results are the same - applied patch just "skews up" ntpd, while
there are no any problems with vanilla kernels.

Is the patch incorrect in any way?

--
Zaar
The patch ajusts kernel internal clock timer to 2000HZ instead of 1000HZ. This
is required to decrease response time of some drivers (currently rocket.ko).

Author: Igor Yanover <igor@yanover.name>
Crafted for 2.6.15 by: Michael Goldman <haizaar@gmail.com>

--- kernel-2.6.15/include/linux/jiffies.h.orig 2006-02-07 12:59:20.000000000 +0200
+++ kernel-2.6.15/include/linux/jiffies.h 2006-02-07 13:00:50.000000000 +0200
@@ -38,6 +38,8 @@
# define SHIFT_HZ 9
#elif HZ >= 768 && HZ < 1536
# define SHIFT_HZ 10
+#elif HZ >= 1536 && HZ < 3072
+# define SHIFT_HZ 11
#else
# error You lose.
#endif
--- kernel-2.6.15/kernel/Kconfig.hz.orig 2006-01-03 05:21:10.000000000 +0200
+++ kernel-2.6.15/kernel/Kconfig.hz 2006-02-07 18:44:03.000000000 +0200
@@ -36,6 +36,11 @@
1000 HZ is the preferred choice for desktop systems and other
systems requiring fast interactive responses to events.

+ config HZ_2000
+ bool "2000 HZ"
+ help
+ 2000 HZ is hand crafted for software realtime. Use on your own risk.
+
endchoice

config HZ
@@ -43,4 +48,5 @@
default 100 if HZ_100
default 250 if HZ_250
default 1000 if HZ_1000
+ default 2000 if HZ_2000






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