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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: Fri, 17 Jul 2015 16:03:30 +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>
----- On Jul 17, 2015, at 6:58 AM, OndÅej BÃlka firstname.lastname@example.org wrote:
>> If we invoke this per-thread registration directly in the glibc NPTL
>> in start_thread, do you think it would fit your requirements ?
> A generic solution would be adding eager initialization of thread_local
> variables which would fix more performance problems.
Concretely, what code would be in charge of this initialization ?
What changes does "eager initialization" imply from the current
> 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.