linux-kernel - Re: [PATCH] selftests/mm: Introduce a test program to assess swap entry allocation for thp

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Message-ID: <87sex710u2.fsf@yhuang6-desk2.ccr.corp.intel.com>
Date: Fri, 21 Jun 2024 10:33:41 +0800
From: "Huang, Ying" <ying.huang@...el.com>
To: David Hildenbrand <david@...hat.com>
Cc: Ryan Roberts <ryan.roberts@....com>,  Barry Song <21cnbao@...il.com>,
  akpm@...ux-foundation.org,  shuah@...nel.org,  linux-mm@...ck.org,
  chrisl@...nel.org,  hughd@...gle.com,  kaleshsingh@...gle.com,
  kasong@...cent.com,  linux-kernel@...r.kernel.org,
  linux-kselftest@...r.kernel.org,  Barry Song <v-songbaohua@...o.com>,
 Philip Li <philip.li@...el.com>
Subject: Re: [PATCH] selftests/mm: Introduce a test program to assess swap
 entry allocation for thp_swapout

David Hildenbrand <david@...hat.com> writes:

> On 20.06.24 11:04, Ryan Roberts wrote:
>> On 20/06/2024 01:26, Barry Song wrote:
>>> From: Barry Song <v-songbaohua@...o.com>
>>>
>>> Both Ryan and Chris have been utilizing the small test program to aid
>>> in debugging and identifying issues with swap entry allocation. While
>>> a real or intricate workload might be more suitable for assessing the
>>> correctness and effectiveness of the swap allocation policy, a small
>>> test program presents a simpler means of understanding the problem and
>>> initially verifying the improvements being made.
>>>
>>> Let's endeavor to integrate it into the self-test suite. Although it
>>> presently only accommodates 64KB and 4KB, I'm optimistic that we can
>>> expand its capabilities to support multiple sizes and simulate more
>>> complex systems in the future as required.
>> I'll try to summarize the thread with Huang Ying by suggesting this
>> test program
>> is "neccessary but not sufficient" to exhaustively test the mTHP swap-out path.
>> I've certainly found it useful and think it would be a valuable addition to the
>> tree.
>> That said, I'm not convinced it is a selftest; IMO a selftest should
>> provide a
>> clear pass/fail result against some criteria and must be able to be run
>> automatically by (e.g.) a CI system.
>
> Likely we should then consider moving other such performance-related
> thingies out of the selftests?

I think that it's good to distinguish between functionality and
performance tests.  For example, 0-day test system will use virtual
machines to do some functionality tests to improve efficiency.  But it's
not good to run performance tests in such kind of virtual machines.

--
Best Regards,
Huang, Ying