Questions tagged [perf]
Perf is a profiler tool for Linux 2.6+ based systems.
perf
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Why does perf record --branch-any affect the CPU usage of the process?
The background is that I want to collect lbr events on the machine for pgo. But when I execute perf, I find that the CPU utilization of the processes running on the machine will increase. I am ...
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How to get llc misses using perf
In perf manual, I find two metrics to obtain llc misses:
PERF_COUNT_HW_CACHE_MISSES Cache misses.
Usually this indicates Last Level Cache misses;
PERF_COUNT_HW_CACHE_LL
for measuring Last-Level ...
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Linux read() occasionally returns "No child processes" (errno 10) when reading perf counters after kernel update
I have C++ program that collects hardware counters using the perf_event_open and read methods on CentOS9 Stream.
The code was working perfectly fine with kernel version 5.14.0-319.el9.x86_64. After a ...
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Why am I getting cache miss while accessing a variable, only updated by the same thread?
I am trying to measure cache misses in a multi-threaded application using perf_event_open on Linux. The code involves two threads: Thread t1, that updates an aligned integer (x) and another thread t2 ...
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CPython: what happens when the take_gil function calls the drop_gil function
I'm using perf probes to profile the GIL contention in a multithreaded Python application and I find sequences where the take_gil function calls drop_gil as shown in the following perf script dump of ...
- 5,717
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perf report: Why is said my function is calling main?
This is an excerpt of a perf report:
Samples: 47K of event 'cycles', Event count (approx.): 22843195013
Children Self Command Shared Object Symbol
+ 97.13% 0.01% ...
- 1,590
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perf on arm cortex-a7 produces no callstacks
I've written a small C++ test program that I want to profile using perf on an arm. Running and profiling the program on my x86 WSL produces expected perf results. However when I profile the program on ...
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How to Link (Simple)Perf Events for ARM CPUs on Android with Concise Metric Description?
Where can I get detailed information about (simple)perf events for ARM CPUs on Android?
simpleperf list specifies many metrics to track:
simpleperf list ...
- 1,707
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How to use perf to collect performance metrics for cgroup?
I want to use --cgroup options with perf to collect performance metrics within a container.
I created the cgroup in the following way:
cgcreate -g cpu:/perf_test
cgcreate -g perf_event:/perf_test
...
- 553
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Perf only has power/energy-pkg
I am currently using
CPU: AMD Ryzen 5800x3D
Kernel: 6.9.6-zen1-1
Perf version: 6.9.2
and I am trying to use perf stat -e power/energy-ram but upon checking /sys/bus/event_source/devices/power/events I ...
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Why perf starts to multiplex events even if there are more counters than events?
I was reading about event multiplexing in perf. In my understanding, multiplexing only happens when there is more events than counters. However, tracking the following 3 events already causes ...
- 189
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Using epoll on a sampling perf_event_open file descriptor returns EPOLLHUP
I am writing a program that uses the Linux perf api to measure the number of instructions run by a program, and I want to receive a notification once the child process reaches a given number of ...
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Is it possible to exclude a pid from perf record (but capture all others)?
I want to run the perf record, but filter out a few pids. Reading the perf record doc I am little confused as to how to mention the pid filter. This does not seems to work:
perf record -e cycles --...
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Using `perf` on the host machine, the symbols of the processes in the container cannot be displayed
My goal is to use perf record on the host machine to collect the hot symbols of all processes, including those in the container.
But I found that the symbol column of the process in the container only ...
- 141
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How can I make perf find symbols in my golang program
I want to use perf and FlameGraph to generate a cpu usage flamegraph of my golang program.
$ go build -gcflags=all="-N -l" -o my_program ./*.go # Compile with debug info.
$ ./my_program
$ ...
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