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authorVladimir Mezentsev <vladimir.mezentsev@oracle.com>2022-06-14 14:16:24 -0700
committerVladimir Mezentsev <vladimir.mezentsev@oracle.com>2022-06-14 14:16:24 -0700
commita675e77e55759bad4501cbaaba36fa18dad2339d (patch)
tree3566c37a3f6079558b7afc931f0e906140a3ea5c /gprofng
parent08328cfbafcebac5dac058e2d568d9b2fd3ee478 (diff)
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gprofng docs: provide help for <rate> == <interval>
The help message from 'gprofng collect app -h', in the section on <rate> == <interval>, had a dangling reference to a non-existent manpage. Provide basic info, including reasons for caution.
Diffstat (limited to 'gprofng')
-rw-r--r--gprofng/common/hwctable.c20
1 files changed, 18 insertions, 2 deletions
diff --git a/gprofng/common/hwctable.c b/gprofng/common/hwctable.c
index bc441e1..a1422b6 100644
--- a/gprofng/common/hwctable.c
+++ b/gprofng/common/hwctable.c
@@ -5091,8 +5091,24 @@ hwc_usage_internal (int forKernel, FILE *f_usage, const char *cmd, const char *d
fprintf (f_usage, GTXT (" `lo' per-thread maximum rate of ~10 samples/second\n"));
fprintf (f_usage, GTXT (" `on' per-thread maximum rate of ~100 samples/second\n"));
fprintf (f_usage, GTXT (" `hi' per-thread maximum rate of ~1000 samples/second\n\n"));
- fprintf (f_usage, GTXT (" <rate> == <interval>\n"));
- fprintf (f_usage, GTXT (" event interval; see collect (1) for details\n\n"));
+ fprintf (f_usage, GTXT (" <rate> == <interval>\n"
+ " Fixed event interval value to trigger a sample.\n"
+ " Smaller intervals imply more frequent samples.\n"
+ " Example: when counting cycles on a 2 GHz processor,\n"
+ " an interval of 2,000,003 implies ~1000 samples/sec\n"
+ "\n"
+ " Use this feature with caution, because:\n"
+ " (1) Frequent sampling increases overhead and may disturb \n"
+ " other applications on your system.\n"
+ " (2) Event counts vary dramatically depending on the event \n"
+ " and depending on the application.\n"
+ " (3) A fixed event interval disables any other gprofng\n"
+ " internal mechanisms that may limit event rates.\n"
+ "\n"
+ " Guidelines: Aim at <1000 events per second. Start by \n"
+ " collecting with the 'hi' option; in the experiment overview,\n"
+ " notice how many events are recorded per second; divide by\n"
+ " 1000, and use that as your starting point.\n\n"));
fprintf (f_usage, GTXT (" A comma ',' followed immediately by white space may be omitted.\n\n"));
}