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Re: 'simple' futex interface [Was: [PATCH v3 1/4] futex: Implement mechanism to wait on any of several futexes]
- From: Florian Weimer <fweimer at redhat dot com>
- To: André Almeida <andrealmeid at collabora dot com>
- Cc: Peter Zijlstra <peterz at infradead dot org>, "Pierre-Loup A. Griffais" <pgriffais at valvesoftware dot com>, Thomas Gleixner <tglx at linutronix dot de>, linux-kernel at vger dot kernel dot org, kernel at collabora dot com, krisman at collabora dot com, shuah at kernel dot org, linux-kselftest at vger dot kernel dot org, rostedt at goodmis dot org, ryao at gentoo dot org, dvhart at infradead dot org, mingo at redhat dot com, z dot figura12 at gmail dot com, steven at valvesoftware dot com, steven at liquorix dot net, malteskarupke at web dot de, carlos at redhat dot com, adhemerval dot zanella at linaro dot org, libc-alpha at sourceware dot org, linux-api at vger dot kernel dot org
- Date: Thu, 05 Mar 2020 17:25:23 +0100
- Subject: Re: 'simple' futex interface [Was: [PATCH v3 1/4] futex: Implement mechanism to wait on any of several futexes]
- References: <20200228190717.GM18400@hirez.programming.kicks-ass.net> <20200228194958.GO14946@hirez.programming.kicks-ass.net> <87tv3aflqm.fsf@nanos.tec.linutronix.de> <967d5047-2cb6-d6d8-6107-edb99a4c9696@valvesoftware.com> <87o8thg031.fsf@nanos.tec.linutronix.de> <beb82055-96fa-cb64-a06e-9d7a0946587b@valvesoftware.com> <20200303120050.GC2596@hirez.programming.kicks-ass.net> <87pndth9ur.fsf@oldenburg2.str.redhat.com> <20200303132150.GD2596@hirez.programming.kicks-ass.net> <878skhh7og.fsf@oldenburg2.str.redhat.com> <20200303150104.GE2596@hirez.programming.kicks-ass.net> <52406c54-60b3-dcfe-65d8-4c425459e37b@collabora.com>
* André Almeida:
> Thanks everyone for the feedback around our mechanism. Are the
> performance benefits of implementing a syscall to wait on a single futex
> significant enough to maintain it instead of just using
> `sys_futex_waitv()` with `nr_waiters = 1`? If we join both cases in a
> single interface, we may even add a new member for NUMA hint in `struct
> futex_wait`.
Some seccomp user might want to verify the address, and that's easier if
it's in an argument. But that's just a rather minor aspect.
Do you propose to drop the storage requirement for the NUMA hint
next to the futex completely?
Thanks,
Florian