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Re: [RFC PATCH] getcpu_cache system call: caching current CPU number (x86)
- From: Mathieu Desnoyers <mathieu dot desnoyers at efficios dot com>
- To: OndÅej BÃlka <neleai at seznam dot cz>
- Cc: Ben Maurer <bmaurer at fb dot com>, Paul Turner <pjt at google dot com>, Andrew Hunter <ahh at google dot com>, Peter Zijlstra <peterz at infradead dot org>, Ingo Molnar <mingo at redhat dot com>, rostedt <rostedt at goodmis dot org>, "Paul E. McKenney" <paulmck at linux dot vnet dot ibm dot com>, Josh Triplett <josh at joshtriplett dot org>, Lai Jiangshan <laijs at cn dot fujitsu dot com>, Linus Torvalds <torvalds at linux-foundation dot org>, Andrew Morton <akpm at linux-foundation dot org>, linux-api <linux-api at vger dot kernel dot org>, libc-alpha <libc-alpha at sourceware dot org>
- Date: Sat, 18 Jul 2015 02:43:25 +0000 (UTC)
- Subject: Re: [RFC PATCH] getcpu_cache system call: caching current CPU number (x86)
- Authentication-results: sourceware.org; auth=none
- References: <1436724386-30909-1-git-send-email-mathieu dot desnoyers at efficios dot com> <5CDDBDF2D36D9F43B9F5E99003F6A0D48D5F39C6 at PRN-MBX02-1 dot TheFacebook dot com> <587954201 dot 31 dot 1436808992876 dot JavaMail dot zimbra at efficios dot com> <20150717105859 dot GB21915 at domone> <626545401 dot 1010 dot 1437149010438 dot JavaMail dot zimbra at efficios dot com> <20150717224353 dot GA7150 at domone>
----- On Jul 17, 2015, at 6:43 PM, OndÅej BÃlka neleai@seznam.cz wrote:
> On Fri, Jul 17, 2015 at 04:03:30PM +0000, Mathieu Desnoyers wrote:
>> ----- On Jul 17, 2015, at 6:58 AM, OndÅej BÃlka neleai@seznam.cz wrote:
>> [...]
>> >> If we invoke this per-thread registration directly in the glibc NPTL
>> >> implementation,
>> >> in start_thread, do you think it would fit your requirements ?
>> >>
>
[...]
>> > Second would be write patch to libc adding function
>> > pthread_create_add_hook_np to register function that would be ran after
>> > each thread creation.
>>
>> Do you suggest that this callback should be registered once per thread,
>> or somehow attached to pthread_attr_t ? As maintainer of lttng-ust,
>> where we need some control over our own threads, but where we want minimal
>> impact on the overall application, I would really prefer if we can attach
>> the callback to pthread_attr_t.
>>
> Could you elaborate. I was suggesting per-thread callback, what do you
> want to do with pthread_attr_t?
Hrm, nevermind, even in the context of lttng-ust, I'd want the callback to
be called for every thread in the application. Therefore, registering this
callback once per process seems to make sense.
Thanks,
Mathieu
--
Mathieu Desnoyers
EfficiOS Inc.
http://www.efficios.com