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[109.252.193.60]) by smtp.googlemail.com with ESMTPSA id q26sm346138lfm.53.2021.03.24.15.11.06 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Wed, 24 Mar 2021 15:11:06 -0700 (PDT) Subject: Re: [PATCH v7] mm: cma: support sysfs To: John Hubbard , Minchan Kim , Andrew Morton Cc: linux-mm , LKML , gregkh@linuxfoundation.org, surenb@google.com, joaodias@google.com, willy@infradead.org, Colin Ian King References: <20210324205503.2132082-1-minchan@kernel.org> <65840bfd-4471-7c8d-ce71-c4705baf3bfe@gmail.com> <0ac4d495-eece-fb71-d334-a46e069b0c35@nvidia.com> From: Dmitry Osipenko Message-ID: <0396987d-1331-51a0-83f4-0c49dd3e150c@gmail.com> Date: Thu, 25 Mar 2021 01:11:06 +0300 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: <0ac4d495-eece-fb71-d334-a46e069b0c35@nvidia.com> Content-Type: text/plain; charset=utf-8 Content-Language: en-US X-Rspamd-Server: rspam03 X-Rspamd-Queue-Id: 5D4BCD5 X-Stat-Signature: shu8p173ug9wdzh1rw8dtwd4hzpntgza Received-SPF: none (gmail.com>: No applicable sender policy available) receiver=imf29; identity=mailfrom; envelope-from=""; helo=mail-lj1-f172.google.com; client-ip=209.85.208.172 X-HE-DKIM-Result: pass/pass X-HE-Tag: 1616623867-149324 Content-Transfer-Encoding: quoted-printable X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: 25.03.2021 01:01, John Hubbard =D0=BF=D0=B8=D1=88=D0=B5=D1=82: > On 3/24/21 2:31 PM, Dmitry Osipenko wrote: >> ... >>> +#include >>> + >>> +struct cma_kobject { >>> +=C2=A0=C2=A0=C2=A0 struct cma *cma; >>> +=C2=A0=C2=A0=C2=A0 struct kobject kobj; >> >> If you'll place the kobj as the first member of the struct, then >> container_of will be a no-op. >> >=20 > However, *this does not matter*. Let's not get carried away. If > container_of() ends up as a compile-time addition of +8, instead > of +0, there is not going to be a visible effect in the world. > Or do you have some perf data to the contrary? >=20 > Sometimes these kinds of things matter. But other times, they are > just pointless to fret about, and this is once such case. Performance is out of question here, my main point is about maintaining a good coding style. Otherwise there is no point in not embedding kobj into cma struct as well, IMO.