From: "sapatel at redhat dot com" <sourceware-bugzilla@sourceware.org>
To: systemtap@sourceware.org
Subject: [Bug bpf/25218] New: stapbpf losing perf_events
Date: Fri, 22 Nov 2019 23:13:00 -0000 [thread overview]
Message-ID: <bug-25218-6586@http.sourceware.org/bugzilla/> (raw)
https://sourceware.org/bugzilla/show_bug.cgi?id=25218
Bug ID: 25218
Summary: stapbpf losing perf_events
Product: systemtap
Version: unspecified
Status: NEW
Severity: normal
Priority: P2
Component: bpf
Assignee: systemtap at sourceware dot org
Reporter: sapatel at redhat dot com
Target Milestone: ---
When there is frequent output from a script, it appears that stapbpf loses some
perf_events which leads to errors. Consider the script below.
global count
probe kernel.function("vfs_read") {
count++
printf("Beginning: %d\n", count)
printf("Middle: %d\n", count)
printf("End: %d\n", count)
}
Output:
...
...
Beginning: 13700
Middle: 13700
End: 13700
Beginning: 13701
Middle: 13701
End: 13701
WARNING: lost 359 perf_events on cpu 2
bpfinterp.cxx:421: printf already started
WARNING: /home/sapatel/stap_head/install/bin/stapbpf exited with signal: 6
(Aborted)
However, if the output is redirected to a file instead, the perf_events are not
lost, and the script proceeds as expected.
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next reply other threads:[~2019-11-22 23:13 UTC|newest]
Thread overview: 4+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-11-22 23:13 sapatel at redhat dot com [this message]
2019-11-22 23:16 ` [Bug bpf/25218] " sapatel at redhat dot com
2019-11-22 23:46 ` [Bug bpf/25218] stapbpf loses perf_events when writing to interactive terminal me at serhei dot io
2019-11-25 18:22 ` me at serhei dot io
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