From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: linux-arch@vger.kernel.org, Hanjun Guo <guohanjun@huawei.com>,
Arnd Bergmann <arnd@arndb.de>,
dave.dice@oracle.com, Jan Glauber <jglauber@marvell.com>,
x86@kernel.org, Will Deacon <will.deacon@arm.com>,
linux@armlinux.org.uk, linux-kernel@vger.kernel.org,
Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
hpa@zytor.com, Alex Kogan <alex.kogan@oracle.com>,
Steven Sistare <steven.sistare@oracle.com>,
Thomas Gleixner <tglx@linutronix.de>,
Daniel Jordan <daniel.m.jordan@oracle.com>,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v8 4/5] locking/qspinlock: Introduce starvation avoidance into CNA
Date: Mon, 3 Feb 2020 16:28:07 +0100 [thread overview]
Message-ID: <20200203152807.GK14914@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <6d11b22b-2fb5-7dea-f88b-b32f1576a5e0@redhat.com>
On Mon, Feb 03, 2020 at 09:59:12AM -0500, Waiman Long wrote:
> On 2/3/20 8:45 AM, Peter Zijlstra wrote:
> > Presumably you have a workload where CNA is actually a win? That is,
> > what inspired you to go down this road? Which actual kernel lock is so
> > contended on NUMA machines that we need to do this?
>
> Today, a 2-socket Rome server can have 128 cores and 256 threads. If we
> scale up more, we could easily have more than 1000 threads in a system.
> With that many logical cpus available, it is easy to envision some heavy
> spinlock contention can happen fairly regularly. This patch can
> alleviate the congestion and improve performance under that
> circumstance. Of course, the specific locks that are contended will
> depend on the workloads.
Not the point. If there isn't an issue today, we don't have anything to
fix.
Furthermore, we've always adressed specific issues by looking at the
locking granularity, first.
So again, what specific lock inspired all these patches?
WARNING: multiple messages have this Message-ID (diff)
From: Peter Zijlstra <peterz@infradead.org>
To: Waiman Long <longman@redhat.com>
Cc: Alex Kogan <alex.kogan@oracle.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
Subject: Re: [PATCH v8 4/5] locking/qspinlock: Introduce starvation avoidance into CNA
Date: Mon, 3 Feb 2020 16:28:07 +0100 [thread overview]
Message-ID: <20200203152807.GK14914@hirez.programming.kicks-ass.net> (raw)
Message-ID: <20200203152807.S_wuDylCfVr1LRzv-YryyEadP-RFs7C5HH5zgzWoSTQ@z> (raw)
In-Reply-To: <6d11b22b-2fb5-7dea-f88b-b32f1576a5e0@redhat.com>
On Mon, Feb 03, 2020 at 09:59:12AM -0500, Waiman Long wrote:
> On 2/3/20 8:45 AM, Peter Zijlstra wrote:
> > Presumably you have a workload where CNA is actually a win? That is,
> > what inspired you to go down this road? Which actual kernel lock is so
> > contended on NUMA machines that we need to do this?
>
> Today, a 2-socket Rome server can have 128 cores and 256 threads. If we
> scale up more, we could easily have more than 1000 threads in a system.
> With that many logical cpus available, it is easy to envision some heavy
> spinlock contention can happen fairly regularly. This patch can
> alleviate the congestion and improve performance under that
> circumstance. Of course, the specific locks that are contended will
> depend on the workloads.
Not the point. If there isn't an issue today, we don't have anything to
fix.
Furthermore, we've always adressed specific issues by looking at the
locking granularity, first.
So again, what specific lock inspired all these patches?
next prev parent reply other threads:[~2020-02-03 15:28 UTC|newest]
Thread overview: 72+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-12-30 19:40 [PATCH v8 0/5] Add NUMA-awareness to qspinlock Alex Kogan
2019-12-30 19:40 ` Alex Kogan
2019-12-30 19:40 ` [PATCH v8 1/5] locking/qspinlock: Rename mcs lock/unlock macros and make them more generic Alex Kogan
2019-12-30 19:40 ` Alex Kogan
2019-12-30 19:40 ` [PATCH v8 2/5] locking/qspinlock: Refactor the qspinlock slow path Alex Kogan
2019-12-30 19:40 ` Alex Kogan
2019-12-30 19:40 ` [PATCH v8 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2019-12-30 19:40 ` Alex Kogan
2020-01-03 22:14 ` Waiman Long
2020-01-03 22:14 ` Waiman Long
2020-01-06 15:02 ` Alex Kogan
2020-01-06 15:02 ` Alex Kogan
2020-01-21 13:48 ` Peter Zijlstra
2020-01-21 13:48 ` Peter Zijlstra
2020-01-21 14:42 ` Peter Zijlstra
2020-01-21 14:42 ` Peter Zijlstra
2019-12-30 19:40 ` [PATCH v8 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2019-12-30 19:40 ` Alex Kogan
2020-01-06 15:33 ` Waiman Long
2020-01-06 15:33 ` Waiman Long
2020-01-21 13:29 ` Peter Zijlstra
2020-01-21 13:29 ` Peter Zijlstra
2020-01-21 13:50 ` Peter Zijlstra
2020-01-21 13:50 ` Peter Zijlstra
2020-01-21 21:19 ` Daniel Bristot de Oliveira
2020-01-21 21:19 ` Daniel Bristot de Oliveira
2020-01-21 15:45 ` Waiman Long
2020-01-21 15:45 ` Waiman Long
[not found] ` <3862F8A1-FF9B-40AD-A88E-2C0BA7AF6F58@oracle.com>
2020-01-24 7:52 ` Peter Zijlstra
2020-01-24 7:52 ` Peter Zijlstra
2020-01-24 14:42 ` Waiman Long
2020-01-24 15:13 ` Peter Zijlstra
2020-01-24 15:13 ` Peter Zijlstra
2020-01-24 15:19 ` Waiman Long
2020-01-24 15:19 ` Waiman Long
[not found] ` <8D3AFB47-B595-418C-9568-08780DDC58FF@oracle.com>
[not found] ` <714892cd-d96f-4d41-ae8b-d7b7642a6e3c@redhat.com>
2020-01-25 11:16 ` Peter Zijlstra
2020-01-25 11:16 ` Peter Zijlstra
[not found] ` <1669BFDE-A1A5-4ED8-B586-035460BBF68A@oracle.com>
[not found] ` <45660873-731a-a810-8c57-1a5a19d266b4@redhat.com>
2020-01-24 18:51 ` Waiman Long
2020-01-24 18:51 ` Waiman Long
2020-01-25 11:20 ` Peter Zijlstra
2020-01-25 11:20 ` Peter Zijlstra
2020-01-25 19:57 ` Waiman Long
[not found] ` <693E6287-E37C-4C5D-BE33-B3D813BE505D@oracle.com>
2020-01-24 21:12 ` Waiman Long
2020-01-24 21:12 ` Waiman Long
2020-01-24 21:27 ` Alex Kogan
2020-01-25 0:38 ` Waiman Long
2020-01-25 0:38 ` Waiman Long
2020-01-25 11:19 ` Peter Zijlstra
2020-01-25 11:19 ` Peter Zijlstra
2020-01-30 22:05 ` Alex Kogan
2020-02-03 13:45 ` Peter Zijlstra
2020-02-03 13:45 ` Peter Zijlstra
2020-02-03 14:59 ` Waiman Long
2020-02-03 14:59 ` Waiman Long
2020-02-03 15:28 ` Peter Zijlstra [this message]
2020-02-03 15:28 ` Peter Zijlstra
2020-02-03 15:47 ` Waiman Long
[not found] ` <83762715-F68C-42DF-9B41-C4C48DF6762F@oracle.com>
2020-02-04 17:27 ` Peter Zijlstra
2020-02-04 17:27 ` Peter Zijlstra
2020-02-04 17:39 ` Waiman Long
2020-02-04 17:39 ` Waiman Long
2020-02-04 17:53 ` Alex Kogan
2019-12-30 19:40 ` [PATCH v8 5/5] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan
2019-12-30 19:40 ` Alex Kogan
2020-01-22 9:56 ` Peter Zijlstra
2020-01-22 9:56 ` Peter Zijlstra
2020-01-06 15:48 ` [PATCH v8 0/5] Add NUMA-awareness to qspinlock Waiman Long
2020-01-06 15:48 ` Waiman Long
2020-01-08 5:09 ` Shijith Thotton
2020-01-08 5:09 ` Shijith Thotton
2020-01-21 9:21 ` Shijith Thotton
2020-01-21 9:21 ` Shijith Thotton
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