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([2601:282:8200:4c:f2e:a7f7:d853:1e3]) by smtp.gmail.com with ESMTPSA id a10sm12034794ilv.44.2022.01.26.10.37.21 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 26 Jan 2022 10:37:22 -0800 (PST) Subject: Re: [PATCH 1/3] selftests/zram: Remove obsolete max_comp_streams interface To: Petr Vorel Cc: "xuyang2018.jy@fujitsu.com" , "linux-kselftest@vger.kernel.org" , "shuah@kernel.org" , "linux-kernel@vger.kernel.org" , "naresh.kamboju@linaro.org" , "aleksei.kodanev@bell-sw.com" , Shuah Khan References: <1639562171-4434-1-git-send-email-xuyang2018.jy@fujitsu.com> <1146337d-718e-a369-1012-224f06bc9c2f@linuxfoundation.org> <61F0D9F7.1080200@fujitsu.com> <590c1f1c-2da1-583a-d055-83c15969cf80@linuxfoundation.org> From: Shuah Khan Message-ID: Date: Wed, 26 Jan 2022 11:37:20 -0700 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:78.0) Gecko/20100101 Thunderbird/78.8.1 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Language: en-US Content-Transfer-Encoding: 8bit Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org On 1/26/22 11:24 AM, Petr Vorel wrote: >> On 1/26/22 12:13 AM, Petr Vorel wrote: >>> Hi all, > >>>> on 2022/1/26 4:33, Shuah Khan wrote : >>>>> On 12/15/21 2:56 AM, Yang Xu wrote: >>>>>> Since kernel commit 43209ea2d17a ("zram: remove max_comp_streams >>>>>> internals"), zram has >>>>>> switched to per-cpu streams. Even kernel still keep this interface for >>>>>> some reasons, but >>>>>> writing to max_comp_stream doesn't take any effect. So remove it. > >>>>> I get that max_comp_stream doesn't do anything since this referenced >>>>> commit. Don't we need this test on older kernels since older kernels >>>>> still support max_comp_stream? > >>>> I read the following info from kernel selftest documentation >>>> https://www.kernel.org/doc/html/latest/dev-tools/kselftest.html > >>>> "The kernel contains a set of “self tests” under the >>>> tools/testing/selftests/ directory. These are intended to be small tests >>>> to exercise individual code paths in the kernel. Tests are intended to >>>> be run after building, installing and booting a kernel." > >>>> So, we can build older kernel(use older kernel source) if we want to >>>> test older kernel. > >>>> IMO, kernel selftest is different from other testsuit(ie ltp, this >>>> shuould think about api changes because ltp may test on different kernel). >>> Yes, that's how I understand the difference with approach of in kselftest - the >>> kernel tree testsuite and LTP - the out-of-tree testsuite. > > >> Removing max_comp_stream test appears to be motivated by the fact it isn't >> needed on newer kernels. > >> Kselftest from mainline can be run on older stable kernels. This is a use-case >> for a lot test rings. The idea is that when a new test gets added for older >> code to regression test a bug, we should be able to run that test on an older >> kernel. This is the reason why we don't remove code that can still test an older >> kernel and make sure it skips gracefully. > > Thanks for clarifying this approach. It might be worth of documenting it in > dev-tools/kselftest.rst. > I will send out a patch clarifying this. thanks, -- Shuah