Count missed samples when estimating total CPU time in ctimer mode #1068
Conversation
This file contains hidden or bidirectional Unicode text that may be interpreted or compiled differently than what appears below. To review, open the file in an editor that reveals hidden Unicode characters.
Learn more about bidirectional Unicode characters
apangin
added a commit
that referenced
this pull request
Dec 3, 2024
krk
pushed a commit
to krk/async-profiler
that referenced
this pull request
Dec 6, 2024
Sign up for free
to join this conversation on GitHub.
Already have an account?
Sign in to comment
1 participant
Add this suggestion to a batch that can be applied as a single commit.
This suggestion is invalid because no changes were made to the code.
Suggestions cannot be applied while the pull request is closed.
Suggestions cannot be applied while viewing a subset of changes.
Only one suggestion per line can be applied in a batch.
Add this suggestion to a batch that can be applied as a single commit.
Applying suggestions on deleted lines is not supported.
You must change the existing code in this line in order to create a valid suggestion.
Outdated suggestions cannot be applied.
This suggestion has been applied or marked resolved.
Suggestions cannot be applied from pending reviews.
Suggestions cannot be applied on multi-line comments.
Suggestions cannot be applied while the pull request is queued to merge.
Suggestion cannot be applied right now. Please check back later.
Description
Leverage
si_overrunfor scaling total CPU time counted inctimermode.Motivation and context
Sampling frequency in ctimer mode depends on the kernel
CONFIG_HZconfiguration, which is typically 250 or 100 Hz. This means, profiling intervals should be multiple of 4ms/10ms, or they will not work as expected.Fortunately, if profiling interval is set to a smaller value, Linux will pass the number of missed samples (number of times the timer would have triggered) in
si_overrunfield ofsiginfo. We can use this value to compute actual CPU time.How has this been tested?
Usual tests + new
ctimerTotalanditimerTotalunit tests.By submitting this pull request, I confirm that my contribution is made under the terms of the Apache 2.0 license.