From: John Levon <movement@us...> - 2002-02-09 21:02:49
Update of /cvsroot/oprofile/oprofile/doc
In directory usw-pr-cvs1:/tmp/cvs-serv3834/doc
rtc patch from bob
RCS file: /cvsroot/oprofile/oprofile/doc/oprofile.sgml,v
retrieving revision 1.77
retrieving revision 1.78
diff -u -d -r1.77 -r1.78
--- oprofile.sgml 8 Feb 2002 05:27:20 -0000 1.77
+++ oprofile.sgml 9 Feb 2002 21:02:46 -0000 1.78
@@ -605,7 +605,9 @@
RTC mode is less capable than the hardware counters mode; in particular, it is unable to profile sections of
the kernel where interrupts are disabled. There is just one available event, "RTC interrupts", and its value
corresponds to the number of interrupts generated per second (that is, a higher number means a better profiling
-resolution, and higher overhead). Note that the value passed is rounded up to a power of two.
+resolution, and higher overhead). The current implementation of the real-time clock supports only power-of-two
+sampling rates from 2 to 4096 per second. Other values within this range are rounded to the nearest power of
Setting the value from the GUI should be straightforward. On the command line, you need to specify the
@@ -613,7 +615,9 @@
<para><command>op_start —map-file=/boot/2.4.0ac12/System.map —vmlinux=/boot/2.4.0ac12/vmlinux --rtc-value=256</command></para>
-Note the sysctl tree described in the next section is different when the RTC is being used.
+Note the sysctl tree described in the next section is different when the RTC is being used. In particular,
+the file <filename>/proc/sys/dev/oprofile/rtc_value</filename> is used by the tools to set the desired RTC
+sampling rate, and will reflect the actual sampling rate after profiling has started.