Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67;
Subject: Re: [PATCH RESEND v8 1/2] sched/numa: introduce per-cgroup NUMA
 locality info
To:     Peter Zijlstra <peterz@infradead.org>
Cc:     Mel Gorman <mgorman@suse.de>, Ingo Molnar <mingo@redhat.com>,
        Juri Lelli <juri.lelli@redhat.com>,
        Vincent Guittot <vincent.guittot@linaro.org>,
        Dietmar Eggemann <dietmar.eggemann@arm.com>,
        Steven Rostedt <rostedt@goodmis.org>,
        Ben Segall <bsegall@google.com>,
        Luis Chamberlain <mcgrof@kernel.org>,
        Kees Cook <keescook@chromium.org>,
        Iurii Zaikin <yzaikin@google.com>,
        Michal Koutn? <mkoutny@suse.com>,
        linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org,
        linux-doc@vger.kernel.org,
        "Paul E. McKenney" <paulmck@linux.ibm.com>,
        Randy Dunlap <rdunlap@infradead.org>,
        Jonathan Corbet <corbet@lwn.net>
References: <fe56d99d-82e0-498c-ae44-f7cde83b5206@linux.alibaba.com>
 <cde13472-46c0-7e17-175f-4b2ba4d8148a@linux.alibaba.com>
 <20200214151048.GL14914@hirez.programming.kicks-ass.net>
 <20200217115810.GA3420@suse.de>
 <881deb50-163e-442a-41ec-b375cc445e4d@linux.alibaba.com>
 <20200221152824.GH18400@hirez.programming.kicks-ass.net>
From:   =?UTF-8?B?546L6LSH?= <yun.wang@linux.alibaba.com>
Message-ID: <3bd3f4d0-2504-a48c-adea-a28227a81d7a@linux.alibaba.com>
Date:   Mon, 24 Feb 2020 11:09:06 +0800
User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:68.0)
 Gecko/20100101 Thunderbird/68.4.1
MIME-Version: 1.0
In-Reply-To: <20200221152824.GH18400@hirez.programming.kicks-ass.net>
Content-Type: text/plain; charset=utf-8
Content-Language: en-US
Content-Transfer-Encoding: 8bit
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk


On 2020/2/21 下午11:28, Peter Zijlstra wrote:
> On Mon, Feb 17, 2020 at 09:23:52PM +0800, 王贇 wrote:
>> FYI, by monitoring locality, we found that the kvm vcpu thread is not
>> covered by NUMA Balancing, whatever how many maximum period passed, the
>> counters are not increasing, or very slowly, although inside guest we are
>> copying memory.
>>
>> Later we found such task rarely exit to user space to trigger task
>> work callbacks, and NUMA Balancing scan depends on that, which help us
>> realize the importance to enable NUMA Balancing inside guest, with the
>> correct NUMA topo, a big performance risk I'll say :-P
> 
> That's a bug in KVM, see:
> 
>   https://lkml.kernel.org/r/20190801143657.785902257@linutronix.de
>   https://lkml.kernel.org/r/20190801143657.887648487@linutronix.de
> 
> ISTR there being newer versions of that patch-set, but I can't seem to
> find them in a hurry.

Aha, that's exactly the problem we saw, will check~

Regards,
Michael Wang

>