From: "Valdis Klētnieks" <valdis.kletnieks@vt.edu>
To: Theodore Dubois <tbodt@google.com>
Cc: kernelnewbies@kernelnewbies.org, a.p.zijlstra@chello.nl,
linux-kernel@vger.kernel.org
Subject: Re: perf_event wakeup_events = 0
Date: Sat, 07 Sep 2019 18:00:22 -0400 [thread overview]
Message-ID: <970896.1567893622@turing-police> (raw)
In-Reply-To: <123C743E-C322-45DB-8796-BF6B6EE9CA80@google.com>
[-- Warning: decoded text below may be mangled, UTF-8 assumed --]
[-- Attachment #1.1: Type: text/plain; charset=us-ascii, Size: 546 bytes --]
On Sat, 07 Sep 2019 09:14:49 -0700, Theodore Dubois said:
> If I’m reading this right, this is a sampling event which overflows 4000
> times a second. But perf then does a poll call which wakes up on this FD with
> POLLIN after 1.637 seconds, instead of 0.00025 seconds.
No, it *takes a sample* 4,000 times a second. For instance, number of cache line
misses since the last sample. You get an overflow when the counter wraps because
there have been more than 2^32 events since you read the counter.
At least that's my understanding of it.
[-- Attachment #1.2: Type: application/pgp-signature, Size: 832 bytes --]
[-- Attachment #2: Type: text/plain, Size: 170 bytes --]
_______________________________________________
Kernelnewbies mailing list
Kernelnewbies@kernelnewbies.org
https://lists.kernelnewbies.org/mailman/listinfo/kernelnewbies
next prev parent reply other threads:[~2019-09-07 22:01 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-09-06 23:28 perf_event wakeup_events = 0 Theodore Dubois
2019-09-07 13:40 ` Valdis Klētnieks
2019-09-07 16:14 ` Theodore Dubois
2019-09-07 22:00 ` Valdis Klētnieks [this message]
2019-09-07 22:45 ` Valdis Klētnieks
2019-09-07 23:27 ` Theodore Dubois
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=970896.1567893622@turing-police \
--to=valdis.kletnieks@vt.edu \
--cc=a.p.zijlstra@chello.nl \
--cc=kernelnewbies@kernelnewbies.org \
--cc=linux-kernel@vger.kernel.org \
--cc=tbodt@google.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).