Received-SPF: softfail (google.com: domain of transitioning linux-kernel-owner@vger.kernel.org does not designate 23.128.96.19 as permitted sender) client-ip=23.128.96.19;
From:   Thomas Gleixner <tglx@linutronix.de>
To:     Eric Dumazet <edumazet@google.com>
Cc:     Eric Dumazet <eric.dumazet@gmail.com>,
        "Paul E . McKenney" <paulmck@kernel.org>,
        linux-kernel <linux-kernel@vger.kernel.org>,
        "Rafael J . Wysocki" <rafael.j.wysocki@intel.com>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        "H. Peter Anvin" <hpa@zytor.com>,
        the arch/x86 maintainers <x86@kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Subject: Re: [PATCH] x86/cpu: use smp_call_function_many() in
 arch_freq_prepare_all()
In-Reply-To: <CANn89i+aCnUQj+UkRQBQ+mkL3xeFCmSkgeCYx+hmMNmko+EZ4Q@mail.gmail.com>
References: <20220311011715.2440601-1-eric.dumazet@gmail.com>
 <87ee2jo2je.ffs@tglx>
 <CANn89i+aCnUQj+UkRQBQ+mkL3xeFCmSkgeCYx+hmMNmko+EZ4Q@mail.gmail.com>
Date:   Wed, 30 Mar 2022 19:02:36 +0200
Message-ID: <87bkxnnzkj.ffs@tglx>
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

On Wed, Mar 30 2022 at 09:51, Eric Dumazet wrote:
> On Wed, Mar 30, 2022 at 8:58 AM Thomas Gleixner <tglx@linutronix.de> wrote:
>> which I hate with a passion because that allows *unpriviledged* user
>> space to inject systemwide IPIs every 10ms just to read these counters
>> which are providing not more than some estimate and are of no value for
>> the only sane use case of /proc/cpuinfo, i.e. #1 above.
>
> You do realize that before my patch, this is already happening ?
>
> My "optimization" simply replace an open loop of individual IPI with
> use of the broadcast IPI capability.
>
> Are you saying we should remove IPI broadcast and use loops
> of IPI, one cpu at a time ?

I rather have no IPIs at all...