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;
MIME-Version: 1.0
In-Reply-To: <CAJZ5v0hTTe9zYwYKtoQKjJJbazFeaGVO2SdbaODyvTFiNpGTdw@mail.gmail.com>
References: <20180606122731.GB27707@jra-laptop.brq.redhat.com> <CAJZ5v0hTTe9zYwYKtoQKjJJbazFeaGVO2SdbaODyvTFiNpGTdw@mail.gmail.com>
From:   "Rafael J. Wysocki" <rafael@kernel.org>
Date:   Wed, 6 Jun 2018 14:44:25 +0200
Message-ID: <CAJZ5v0jHgz1OWHfAhvkP_rZX=m7NCuZxqO5LA4or5WtygEZxFw@mail.gmail.com>
Subject: Re: [4.17 regression] Performance drop on kernel-4.17 visible on
 Stream, Linpack and NAS parallel benchmarks
To:     "Rafael J. Wysocki" <rafael@kernel.org>
Cc:     Jakub Racek <jracek@redhat.com>,
        Linux Kernel Mailing List <linux-kernel@vger.kernel.org>,
        "Rafael J. Wysocki" <rjw@rjwysocki.net>,
        Len Brown <lenb@kernel.org>,
        ACPI Devel Maling List <linux-acpi@vger.kernel.org>,
        Peter Zijlstra <peterz@infradead.org>
Content-Type: text/plain; charset="UTF-8"
Sender: linux-kernel-owner@vger.kernel.org
Precedence: bulk

On Wed, Jun 6, 2018 at 2:34 PM, Rafael J. Wysocki <rafael@kernel.org> wrote:
> On Wed, Jun 6, 2018 at 2:27 PM, Jakub Racek <jracek@redhat.com> wrote:
>> Hi,
>>
>> There is a huge performance regression on the 2 and 4 NUMA node systems on
>> stream benchmark with 4.17 kernel compared to 4.16 kernel. Stream, Linpack
>> and NAS parallel benchmarks show upto 50% performance drop.
>>
>> When running for example 20 stream processes in parallel, we see the
>> following behavior:
>>
>> * all processes are started at NODE #1
>> * memory is also allocated on NODE #1
>> * roughly half of the processes are moved to the NODE #0 very quickly. *
>> however, memory is not moved to NODE #0 and stays allocated on NODE #1
>>
>> As the result, half of the processes are running on NODE#0 with memory being
>> still allocated on NODE#1. This leads to non-local memory accesses
>> on the high Remote-To-Local Memory Access Ratio on the numatop charts.
>> So it seems that 4.17 is not doing a good job to move the memory to the
>> right NUMA
>> node after the process has been moved.
>>
>> ----8<----
>>
>> The above is an excerpt from performance testing on 4.16 and 4.17 kernels.
>>
>> For now I'm merely making sure the problem is reported.
>
> OK, and why do you think that it is related to ACPI?

In any case, we need more information here.

Thanks,
Rafael