From: Alex Kogan <alex.kogan@oracle.com>
To: paulmck@kernel.org
Cc: linux-arch@vger.kernel.org, guohanjun@huawei.com,
Arnd Bergmann <arnd@arndb.de>,
Peter Zijlstra <peterz@infradead.org>,
dave.dice@oracle.com, jglauber@marvell.com, x86@kernel.org,
Will Deacon <will.deacon@arm.com>,
linux@armlinux.org.uk, steven.sistare@oracle.com,
linux-kernel@vger.kernel.org, Ingo Molnar <mingo@redhat.com>,
bp@alien8.de, hpa@zytor.com, Waiman Long <longman@redhat.com>,
tglx@linutronix.de, daniel.m.jordan@oracle.com,
linux-arm-kernel <linux-arm-kernel@lists.infradead.org>
Subject: Re: [PATCH v9 0/5] Add NUMA-awareness to qspinlock
Date: Mon, 27 Jan 2020 01:04:45 -0500 [thread overview]
Message-ID: <FB96E148-C72B-4D00-95F0-C4B69A3EE454@oracle.com> (raw)
In-Reply-To: <20200126224245.GA22901@paulmck-ThinkPad-P72>
> On Jan 26, 2020, at 5:42 PM, Paul E. McKenney <paulmck@kernel.org> wrote:
>
> On Sun, Jan 26, 2020 at 07:35:35AM -0800, Paul E. McKenney wrote:
>> On Sat, Jan 25, 2020 at 02:41:39PM -0500, Waiman Long wrote:
>>> On 1/24/20 11:58 PM, Paul E. McKenney wrote:
>>>> On Fri, Jan 24, 2020 at 09:17:05PM -0500, Waiman Long wrote:
>>>>> On 1/24/20 8:59 PM, Waiman Long wrote:
>>>>>>> You called it! I will play with QEMU's -numa argument to see if I can get
>>>>>>> CNA to run for me. Please accept my apologies for the false alarm.
>>>>>>>
>>>>>>> Thanx, Paul
>>>>>>>
>>>>>> CNA is not currently supported in a VM guest simply because the numa
>>>>>> information is not reliable. You will have to run it on baremetal to
>>>>>> test it. Sorry for that.
>>>>> Correction. There is a command line option to force CNA lock to be used
>>>>> in a VM. Use the "numa_spinlock=on" boot command line parameter.
>>>> As I understand it, I need to use a series of -numa arguments to qemu
>>>> combined with the numa_spinlock=on (or =1) on the kernel command line.
>>>> If the kernel thinks that there is only one NUMA node, it appears to
>>>> avoid doing CNA.
>>>>
>>>> Correct?
>>>>
>>>> Thanx, Paul
>>>>
>>> In auto-detection mode (the default), CNA will only be turned on when
>>> paravirt qspinlock is not enabled first and there are at least 2 numa
>>> nodes. The "numa_spinlock=on" option will force it on even when both of
>>> the above conditions are false.
>>
>> Hmmm...
>>
>> Here is my kernel command line taken from the console log:
>>
>> console=ttyS0 locktorture.onoff_interval=0 numa_spinlock=on locktorture.stat_interval=15 locktorture.shutdown_secs=1800 locktorture.verbose=1
>>
>> Yet the string "Enabling CNA spinlock" does not appear.
>>
>> Ah, idiot here needs to enable CONFIG_NUMA_AWARE_SPINLOCKS in his build.
>> Trying again with "--kconfig "CONFIG_NUMA_AWARE_SPINLOCKS=y"...
>
> And after fixing that, plus adding the other three Kconfig options required
> to enable this, I really do see "Enabling CNA spinlock" in the console log.
> Yay!
Great! Your persistence paid off :)
Yet, CNA does not do much interesting here, as it sees only one numa node.
>
> At the end of the 30-minute locktorture exclusive-lock run, I see this:
>
> Writes: Total: 572176565 Max/Min: 54167704/10878216 ??? Fail: 0
>
> This is about a five-to-one ratio. Is this expected behavior, given a
> single NUMA node on a single-socket system with 12 hardware threads?
I’m not sure what is expected here.
I’m guessing that if you boot your guest with the default
(non-CNA/non-paravirt) qspinlock, you will get a similar result.
>
> I will try reader-writer lock next.
>
> Again, should I be using qemu's -numa command-line option to create nodes?
> If so, what would be a sane configuration given 12 CPUs and 512MB of
> memory for the VM? If not, what is a good way to exercise CNA's NUMA
> capabilities within a guest OS?
That’s a good question. Perhaps Longman knows the answer?
Regards,
— Alex
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next prev parent reply other threads:[~2020-01-27 6:06 UTC|newest]
Thread overview: 39+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-01-15 3:59 [PATCH v9 0/5] Add NUMA-awareness to qspinlock Alex Kogan
2020-01-15 3:59 ` [PATCH v9 1/5] locking/qspinlock: Rename mcs lock/unlock macros and make them more generic Alex Kogan
2020-01-15 3:59 ` [PATCH v9 2/5] locking/qspinlock: Refactor the qspinlock slow path Alex Kogan
2020-01-15 3:59 ` [PATCH v9 3/5] locking/qspinlock: Introduce CNA into the slow path of qspinlock Alex Kogan
2020-01-23 9:26 ` Peter Zijlstra
2020-01-23 10:06 ` Peter Zijlstra
2020-01-23 10:16 ` Peter Zijlstra
2020-01-23 11:22 ` Will Deacon
2020-01-23 13:17 ` Peter Zijlstra
2020-01-23 14:15 ` Waiman Long
2020-01-23 15:29 ` Peter Zijlstra
2020-01-15 3:59 ` [PATCH v9 4/5] locking/qspinlock: Introduce starvation avoidance into CNA Alex Kogan
2020-01-23 19:55 ` Waiman Long
2020-01-23 20:39 ` Waiman Long
2020-01-23 23:39 ` Alex Kogan
2020-01-15 3:59 ` [PATCH v9 5/5] locking/qspinlock: Introduce the shuffle reduction optimization " Alex Kogan
2020-01-22 11:45 ` [PATCH v9 0/5] Add NUMA-awareness to qspinlock Lihao Liang
2020-01-22 17:24 ` Waiman Long
2020-01-23 11:35 ` Will Deacon
2020-01-23 15:25 ` Waiman Long
2020-01-23 19:08 ` Waiman Long
2020-01-22 19:29 ` Alex Kogan
2020-01-26 0:32 ` Lihao Liang
2020-01-26 1:58 ` Lihao Liang
2020-01-27 16:01 ` Alex Kogan
2020-01-29 1:39 ` Lihao Liang
2020-01-27 6:16 ` Alex Kogan
2020-01-24 22:24 ` Paul E. McKenney
[not found] ` <6AAE7FC6-F5DE-4067-8BC4-77F27948CD09@oracle.com>
2020-01-25 0:57 ` Paul E. McKenney
2020-01-25 1:59 ` Waiman Long
[not found] ` <adb4fb09-f374-4d64-096b-ba9ad8b35fd5@redhat.com>
2020-01-25 4:58 ` Paul E. McKenney
2020-01-25 19:41 ` Waiman Long
2020-01-26 15:35 ` Paul E. McKenney
2020-01-26 22:42 ` Paul E. McKenney
2020-01-26 23:32 ` Paul E. McKenney
2020-01-27 6:04 ` Alex Kogan [this message]
2020-01-27 14:11 ` Waiman Long
2020-01-27 15:09 ` Paul E. McKenney
[not found] ` <9b3a3f16-5405-b6d1-d023-b85f4aab46dd@redhat.com>
2020-01-27 17:17 ` Waiman Long
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