Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 23.128.96.18 as permitted sender) client-ip=23.128.96.18;
IronPort-SDR: 60st5OJIVbGvXR0TkvkoUJZIai7IN7b3SJv4Go0nvuTHNFv/4JHjC7hGFtaLrOECQWfqRkx2EG
 +qUr+H0m1sXA==
IronPort-SDR: YfsjmzNVqgEX+RdhsWjbLI5ZVirirOpsD1AM61E0QbDtRsiM7gg9190uv5YFGFNZQx9q7f3c/1
 czWhBSzWKi+A==
From:   Andi Kleen <ak@linux.intel.com>
To:     Alex Kogan <alex.kogan@oracle.com>
Cc:     linux@armlinux.org.uk, peterz@infradead.org, mingo@redhat.com,
        will.deacon@arm.com, arnd@arndb.de, longman@redhat.com,
        linux-arch@vger.kernel.org, linux-arm-kernel@lists.infradead.org,
        linux-kernel@vger.kernel.org, tglx@linutronix.de, bp@alien8.de,
        hpa@zytor.com, x86@kernel.org, guohanjun@huawei.com,
        jglauber@marvell.com, steven.sistare@oracle.com,
        daniel.m.jordan@oracle.com, dave.dice@oracle.com
Subject: Re: [PATCH v14 4/6] locking/qspinlock: Introduce starvation avoidance into CNA
References: <20210401153156.1165900-1-alex.kogan@oracle.com>
        <20210401153156.1165900-5-alex.kogan@oracle.com>
Date:   Mon, 12 Apr 2021 23:03:12 -0700
In-Reply-To: <20210401153156.1165900-5-alex.kogan@oracle.com> (Alex Kogan's
        message of "Thu, 1 Apr 2021 11:31:54 -0400")
Message-ID: <87mtu2vhzz.fsf@linux.intel.com>
User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/26.3 (gnu/linux)
MIME-Version: 1.0
Content-Type: text/plain
Precedence: bulk

Alex Kogan <alex.kogan@oracle.com> writes:
>  
> +	numa_spinlock_threshold=	[NUMA, PV_OPS]
> +			Set the time threshold in milliseconds for the
> +			number of intra-node lock hand-offs before the
> +			NUMA-aware spinlock is forced to be passed to
> +			a thread on another NUMA node.	Valid values
> +			are in the [1..100] range. Smaller values result
> +			in a more fair, but less performant spinlock,
> +			and vice versa. The default value is 10.

ms granularity seems very coarse grained for this. Surely
at some point of spinning you can afford a ktime_get? But ok.

Could you turn that into a moduleparm which can be changed at runtime?
Would be strange to have to reboot just to play with this parameter

This would also make the code a lot shorter I guess.

-Andi