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Tue, 05 Dec 2023 16:22:42 -0800 (PST) MIME-Version: 1.0 References: <20231203001501.126339-1-sxwjean@me.com> <20231203001501.126339-4-sxwjean@me.com> In-Reply-To: From: Hyeonggon Yoo <42.hyeyoo@gmail.com> Date: Wed, 6 Dec 2023 09:22:32 +0900 Message-ID: Subject: Re: [PATCH v2 3/3] mm/slub: correct the default value of slub_min_objects in doc To: "Song, Xiongwei" Cc: "sxwjean@me.com" , "vbabka@suse.cz" , "cl@linux.com" , "linux-mm@kvack.org" , "penberg@kernel.org" , "rientjes@google.com" , "iamjoonsoo.kim@lge.com" , "roman.gushchin@linux.dev" , "corbet@lwn.net" , "keescook@chromium.org" , "arnd@arndb.de" , "akpm@linux-foundation.org" , "gregkh@linuxfoundation.org" , "linux-doc@vger.kernel.org" , "linux-kernel@vger.kernel.org" Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable X-Stat-Signature: 4fmyi3x83pkcxz5tzqt8kx31x7u5do5y X-Rspamd-Server: rspam10 X-Rspamd-Queue-Id: 2CA6B100010 X-Rspam-User: X-HE-Tag: 1701822162-580128 X-HE-Meta: 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 gooX2FIM 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 Ed3jzzaf yhTjiTSCsTJwHfJhs2dxxLGmC28i/72mynj6jdjbydL/uIo08reOERZCN72ScpGiJhVq5lYiErwjQnbn3NH+G5QTi8A5Ei6V 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: List-Subscribe: List-Unsubscribe: On Tue, Dec 5, 2023 at 11:11=E2=80=AFPM Song, Xiongwei wrote: > > Hi Hyeonggon, > > > -----Original Message----- > > From: Hyeonggon Yoo <42.hyeyoo@gmail.com> > > Sent: Tuesday, December 5, 2023 8:54 AM > > To: sxwjean@me.com > > Cc: vbabka@suse.cz; cl@linux.com; linux-mm@kvack.org; penberg@kernel.or= g; > > rientjes@google.com; iamjoonsoo.kim@lge.com; roman.gushchin@linux.dev; > > corbet@lwn.net; keescook@chromium.org; arnd@arndb.de; akpm@linux-founda= tion.org; > > gregkh@linuxfoundation.org; linux-doc@vger.kernel.org; linux-kernel@vge= r.kernel.org; Song, > > Xiongwei > > Subject: Re: [PATCH v2 3/3] mm/slub: correct the default value of slub_= min_objects in doc > > > > On Sun, Dec 3, 2023 at 9:16=E2=80=AFAM wrote: > > > > > > From: Xiongwei Song > > > > > > There is no a value assigned to slub_min_objects by default, it alway= s > > > is 0 that is initialized by compiler if no assigned value by command = line. > > > min_objects is calculated based on processor numbers in calculate_ord= er(). > > > For more details, see commit 9b2cd506e5f2 ("slub: Calculate min_objec= ts > > > based on number of processors.") > > > > > > Signed-off-by: Xiongwei Song > > > > While slub_min_objects equals zero by default, 'min_objects' overrides = it to > > 4 * (fls(nr_cpus) + 1) when not set. so when slub_min_objects is not > > set, it would be > > equal to or higher than 4. I'm not sure this level of implementation > > detail is worth documenting. > > commit 9b2cd506e5f2 ("slub: Calculate min_objects based on number of proc= essors.") > has already given "processors min_objects" pair, do we really need to doc= ument > the specific detail? No, I don't think it needs to be documented, but neither do I think "slub_min_objects is 0 by default" is correctly documented... > > Also, I think patch 2 should update Documentation/mm/slub.rst too. > > (slub_$param -> slab_param) > I think people can know slub_$params are still supported by > Documentation/mm/slub.rst, so we don't need to say the info again in > this file. Is it better to do so just before removing slub_$params > completely? If we're deprecating and planning to drop slub_$params in the future, IMHO it'd be less confusing if we change it now, rather than when removing slub_$params completely (probably 10 years later)? Thanks, Hyeonggon > > > --- > > > Documentation/mm/slub.rst | 2 +- > > > 1 file changed, 1 insertion(+), 1 deletion(-) > > > > > > diff --git a/Documentation/mm/slub.rst b/Documentation/mm/slub.rst > > > index be75971532f5..1f4399581449 100644 > > > --- a/Documentation/mm/slub.rst > > > +++ b/Documentation/mm/slub.rst > > > @@ -150,7 +150,7 @@ list_lock once in a while to deal with partial sl= abs. That overhead is > > > governed by the order of the allocation for each slab. The allocatio= ns > > > can be influenced by kernel parameters: > > > > > > -.. slub_min_objects=3Dx (default 4) > > > +.. slub_min_objects=3Dx (default 0) > > > .. slub_min_order=3Dx (default 0) > > > .. slub_max_order=3Dx (default 3 (PAGE_ALLOC_COSTLY_ORDER= )) > > > > > > -- > > > 2.34.1 > > >