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Subject: Re: [PATCH v8 4/5] locking/qspinlock: Introduce starvation avoidance
 into CNA
From:   Alex Kogan <alex.kogan@oracle.com>
In-Reply-To: <20200125111931.GW11457@worktop.programming.kicks-ass.net>
Date:   Thu, 30 Jan 2020 17:05:28 -0500
Cc:     Waiman Long <longman@redhat.com>, linux@armlinux.org.uk,
        Ingo Molnar <mingo@redhat.com>,
        Will Deacon <will.deacon@arm.com>,
        Arnd Bergmann <arnd@arndb.de>, linux-arch@vger.kernel.org,
        linux-arm-kernel <linux-arm-kernel@lists.infradead.org>,
        linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Borislav Petkov <bp@alien8.de>, hpa@zytor.com, x86@kernel.org,
        Hanjun Guo <guohanjun@huawei.com>,
        Jan Glauber <jglauber@marvell.com>,
        Steven Sistare <steven.sistare@oracle.com>,
        Daniel Jordan <daniel.m.jordan@oracle.com>,
        dave.dice@oracle.com
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To:     Peter Zijlstra <peterz@infradead.org>
Sender: linux-kernel-owner@vger.kernel.org
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> On Jan 25, 2020, at 6:19 AM, Peter Zijlstra <peterz@infradead.org> =
wrote:
>=20
> On Fri, Jan 24, 2020 at 01:19:05PM -0500, Alex Kogan wrote:
>=20
>> Is there a lightweight way to identify such a =E2=80=9Cprioritized=E2=80=
=9D thread?
>=20
> No; people might for instance care about tail latencies between their
> identically spec'ed worker tasks.

I would argue that those users need to tune/reduce the intra-node =
handoff
threshold for their needs. Or disable CNA altogether.

In general, Peter, seems like you are not on board with the way Longman
suggested to handle prioritized threads. Am I right?

Thanks,
=E2=80=94 Alex