From: Mark Geisert <mark@maxrnd.com>
To: cygwin@cygwin.com
Subject: Re: posix thread scaling issue
Date: Sat, 2 Sep 2023 20:50:36 -0700 [thread overview]
Message-ID: <1a894e01-0dee-7a14-d94a-40034b88275f@maxrnd.com> (raw)
In-Reply-To: <07386659-68b3-a35d-1402-22684f8e5755@Shaw.ca>
Hi folks,
Brian Inglis via Cygwin wrote:
> On 2023-09-02 12:27, jeff via Cygwin wrote:
[...]
>> When I run cinebench, I can get to 100% cpu utulization (at around 3ghz) on
>> windows.
>
> Chances are the benchmark is designed to handle that:
>
> "When the program is running inside the group, unless it is processor group aware,
> then it can only access other threads in the same group. This means that if a
> multi-threaded program can use 128 threads, if it isn’t built with processor
> groups in mind, then it might only spawn with access to 64."
>
> I also do not know how you would program for that in Cygwin to map onto the
> equivalent Windows function required.
>
> Perhaps one of the developers involved could comment here?
Cygwin doesn't know (at user level) about processor groups as that's a Windows
construct. Cygwin does know about processor affinity and treats all available
processors as a contiguous set, like Linux does, up to 1024 in size. One uses
'taskset' from the util-linux package to assign processes to specific processor(s).
One can deal with thread affinity using pthread_get_affinity_np() and
pthread_set_affinity_np() functions provided by the Cygwin DLL. These are modeled
after the same-named functions in Linux. The internals of these functions do have
to work within the Windows processor group constraints, so not all plausible
set-affinity operations are allowed by Windows. Briefly, you can't move a thread
outside the processor group it's currently in; you have to move its process to the
new group first.
HTH,
..mark
next prev parent reply other threads:[~2023-09-03 3:50 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-09-02 14:57 jeff
2023-09-02 17:56 ` Brian Inglis
2023-09-02 18:27 ` jeff
2023-09-02 19:59 ` Brian Inglis
2023-09-02 20:04 ` jeff
2023-09-03 6:13 ` ASSI
2023-09-03 3:50 ` Mark Geisert [this message]
2023-09-03 4:13 ` Mark Geisert
2023-09-02 19:30 André Bleau
[not found] ` <e36d50d5-75d0-40d5-92e2-02d04092fd77@jeffunit.com>
2023-09-02 21:23 ` André Bleau
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=1a894e01-0dee-7a14-d94a-40034b88275f@maxrnd.com \
--to=mark@maxrnd.com \
--cc=cygwin@cygwin.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 read-only IMAP folder(s) and NNTP newsgroup(s).