linux-kernel - Re: [x86] d55564cfc2: will-it-scale.per_thread

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Message-ID: <X/grPFTgOMvtqEVZ@hirez.programming.kicks-ass.net>
Date:   Fri, 8 Jan 2021 10:51:56 +0100
From:   Peter Zijlstra <peterz@...radead.org>
To:     David Laight <David.Laight@...lab.com>
Cc:     'Linus Torvalds' <torvalds@...ux-foundation.org>,
        Al Viro <viro@...iv.linux.org.uk>,
        kernel test robot <oliver.sang@...el.com>,
        Thomas Gleixner <tglx@...utronix.de>,
        Ingo Molnar <mingo@...nel.org>, Borislav Petkov <bp@...en8.de>,
        LKML <linux-kernel@...r.kernel.org>,
        "lkp@...ts.01.org" <lkp@...ts.01.org>,
        kernel test robot <lkp@...el.com>,
        "Huang, Ying" <ying.huang@...el.com>,
        Feng Tang <feng.tang@...el.com>,
        "zhengjun.xing@...el.com" <zhengjun.xing@...el.com>
Subject: Re: [x86] d55564cfc2: will-it-scale.per_thread_ops -5.8% regression

On Fri, Jan 08, 2021 at 09:37:45AM +0000, David Laight wrote:
> The lack of spinlocks in userspace really kills you.

Glibc has them, but please don't complain about lock holder preemption
issues if you do actually use them ;-)