linux perf file descriptor not readable

[cometkim]

Not sure the exact reason, mitata reported like:

clk: ~2.76 GHz
cpu: Intel(R) Core(TM) i5-9600K CPU @ 3.70GHz
runtime: node 23.6.0 (x64-linux)

benchmark                                     avg (min … max) p75   p99    (min … top 1%)
------------------------------------------------------------- -------------------------------
• Lorem ipsum (ascii)
------------------------------------------------------------- -------------------------------
unicode-segmenter/grapheme                     error: NotOpenForReading
graphemer                                      error: NotOpenForReading
grapheme-splitter                              error: NotOpenForReading
@formatjs/intl-segmenter                       error: NotOpenForReading
unicode-rs/unicode-segmentation (wasm-bindgen) error: NotOpenForReading
Intl.Segmenter                                 error: NotOpenForReading

Downgrading counters to v0.0.5 fixes the issue
cometkim/unicode-segmenter#69

[evanwashere]

interesting that downgrading fixed it because for node there is no difference between 0.0.5 and 0.0.7

[evanwashere]

I released v1.0.27 that ignores errors from hardware counters and continues without them

[evanwashere]

ive searched through linux perf docs but couldn't find any explanation for intermediate file descriptor error. maybe you had some other program using hardware counters at same time?

you should be able to upgrade back to latest version given that there is no actual difference between syscalls they do

[cometkim]

maybe you had some other program using hardware counters at same time?

I don't think so? @mitata/counters 0.0.5~0.0.8 fails in miatata 1.0.26 constantly, but upgrade mitata to 1.0.27 fixed the issue.

clk: ~2.81 GHz
cpu: Intel(R) Core(TM) i5-9600K CPU @ 3.70GHz
runtime: node 23.6.0 (x64-linux)

benchmark                                     avg (min … max) p75   p99    (min … top 1%)
------------------------------------------------------------- -------------------------------
• Lorem ipsum (ascii)
------------------------------------------------------------- -------------------------------
unicode-segmenter/grapheme                      10.01 µs/iter  10.05 µs     █                
                                         (9.90 µs … 10.13 µs)  10.09 µs █▁▁▁█▁█▁█▁█▁█▁▁███▁▁█
                                     NaNP ipc (   NaN% cache)    0.00 branch misses
                             0.00 cycles    0.00 instructions    0.00 c-refs    0.00 c-misses

There appears to be a bug (NaN) in the newly added report, but all existing features work fine.

[cometkim]

I'm not sure what this means exactly, but is it likely that versions of @mitata/counters prior to v0.0.5 weren't working correctly on my machine either?

[evanwashere]

could you provide output of perf list hw command? (need to install linux tools if you don't have perf bin)

[evanwashere]

could also be potentially permissions issue, tried running it with sudo?

[cometkim]

could you provide output of perf list hw command? (need to install linux tools if you don't have perf bin)

Ohhh I got it. perf list hw printed nothing. So I checked my kernel.perf_event_paranoid and it was 4, Ubuntu's default I guess.

After adjusting it with sudo sysctl -w kernel.perf_event_paranoid=1, everything works fine. It would be good to add it to the README.

[evanwashere]

added to docs