Re: [PATCH] mm/slab: rename CONFIG_SLAB to CONFIG_SLAB_DEPRECATED

From: Vlastimil Babka <vbabka@suse.cz>
To: David Rientjes <rientjes@google.com>
Cc: Christoph Lameter <cl@linux.com>,
	Pekka Enberg <penberg@kernel.org>,
	Joonsoo Kim <iamjoonsoo.kim@lge.com>,
	Roman Gushchin <roman.gushchin@linux.dev>,
	Hyeonggon Yoo <42.hyeyoo@gmail.com>,
	Shawn Guo <shawnguo@kernel.org>,
	Sascha Hauer <s.hauer@pengutronix.de>,
	Vladimir Zapolskiy <vz@mleia.com>, Andrew Lunn <andrew@lunn.ch>,
	Gregory Clement <gregory.clement@bootlin.com>,
	Sebastian Hesselbarth <sebastian.hesselbarth@gmail.com>,
	Tony Lindgren <tony@atomide.com>, Qin Jian <qinjian@cqplus1.com>,
	Thomas Bogendoerfer <tsbogend@alpha.franken.de>,
	Dinh Nguyen <dinguyen@kernel.org>,
	"James E . J . Bottomley" <James.Bottomley@hansenpartnership.com>,
	Helge Deller <deller@gmx.de>,
	Yoshinori Sato <ysato@users.sourceforge.jp>,
	Rich Felker <dalias@libc.org>,
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Subject: Re: [PATCH] mm/slab: rename CONFIG_SLAB to CONFIG_SLAB_DEPRECATED
Date: Wed, 24 May 2023 16:27:03 +0200	[thread overview]
Message-ID: <4f690e97-b26c-1705-51e7-0d7ebc77d819@suse.cz> (raw)
In-Reply-To: <be109b49-8510-5887-72ae-738db9945619@google.com>

On 5/24/23 02:29, David Rientjes wrote:
> On Tue, 23 May 2023, Vlastimil Babka wrote:
> 
>> As discussed at LSF/MM [1] [2] and with no objections raised there,
>> deprecate the SLAB allocator. Rename the user-visible option so that
>> users with CONFIG_SLAB=y get a new prompt with explanation during make
>> oldconfig, while make olddefconfig will just switch to SLUB.
>> 
>> In all defconfigs with CONFIG_SLAB=y remove the line so those also
>> switch to SLUB. Regressions due to the switch should be reported to
>> linux-mm and slab maintainers.
>> 
>> [1] https://lore.kernel.org/all/4b9fc9c6-b48c-198f-5f80-811a44737e5f@suse.cz/
>> [2] https://lwn.net/Articles/932201/
>> 
>> Signed-off-by: Vlastimil Babka <vbabka@suse.cz>
> 
> Acked-by: David Rientjes <rientjes@google.com>

Thanks.

> The Kconfig option says that SLAB will be removed in a few cycles.  I 
> think we should wait until at least the next LTS kernel is forked at the 
> end of the year so that users who upgrade to only the LTS releases can be 
> prompted for this change and surface any concerns.  Slab allocation is a 
> critical subsystem, so I presume this is the safest and most responsible 
> way to do the SLAB deprecation.  Hopefully that timeline works for 
> everybody.

Sure, and in fact looking at predicted release dates [1], if the deprecation
goes into 6.5 then 6.7 ("few" == 2) is already end of January 2024, anyway.

[1] https://hansen.beer/~dave/phb/