From: Damien Le Moal <damien.lemoal@opensource.wdc.com>
To: Conor Dooley <conor@kernel.org>, Vlastimil Babka <vbabka@suse.cz>
Cc: Pasha Tatashin <pasha.tatashin@soleen.com>,
Christoph Lameter <cl@linux.com>,
David Rientjes <rientjes@google.com>,
Joonsoo Kim <iamjoonsoo.kim@lge.com>,
Pekka Enberg <penberg@kernel.org>,
Hyeonggon Yoo <42.hyeyoo@gmail.com>,
Matthew Wilcox <willy@infradead.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Linus Torvalds <torvalds@linux-foundation.org>,
"linux-mm@kvack.org" <linux-mm@kvack.org>,
"linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Catalin Marinas <catalin.marinas@arm.com>,
Rustam Kovhaev <rkovhaev@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
Josh Triplett <josh@joshtriplett.org>,
Arnd Bergmann <arnd@arndb.de>,
Russell King <linux@armlinux.org.uk>,
Alexander Shiyan <shc_work@mail.ru>,
Aaro Koskinen <aaro.koskinen@iki.fi>,
Janusz Krzysztofik <jmkrzyszt@gmail.com>,
Tony Lindgren <tony@atomide.com>,
Yoshinori Sato <ysato@users.sourceforge.jp>,
Rich Felker <dalias@libc.org>, Jonas Bonn <jonas@southpole.se>,
Stefan Kristiansson <stefan.kristiansson@saunalahti.fi>,
Stafford Horne <shorne@gmail.com>,
"linux-arm-kernel@lists.infradead.org"
<linux-arm-kernel@lists.infradead.org>,
openrisc@lists.librecores.org, linux-riscv@lists.infradead.org,
linux-sh@vger.kernel.org,
Geert Uytterhoeven <geert@linux-m68k.org>,
Conor.Dooley@microchip.com, Paul Cercueil <paul@crapouillou.net>
Subject: Re: Deprecating and removing SLOB
Date: Sat, 12 Nov 2022 10:40:53 +0900 [thread overview]
Message-ID: <e4076fcb-9736-937d-634b-5b8fb342723e@opensource.wdc.com> (raw)
In-Reply-To: <Y260tkNHc2vFITJ3@spud>
On 11/12/22 05:46, Conor Dooley wrote:
> On Fri, Nov 11, 2022 at 11:33:30AM +0100, Vlastimil Babka wrote:
>> On 11/8/22 22:44, Pasha Tatashin wrote:
>>> On Tue, Nov 8, 2022 at 10:55 AM Vlastimil Babka <vbabka@suse.cz> wrote:
>>>>
>>>> Hi,
>>>>
>>>> as we all know, we currently have three slab allocators. As we discussed
>>>> at LPC [1], it is my hope that one of these allocators has a future, and
>>>> two of them do not.
>>>>
>>>> The unsurprising reasons include code maintenance burden, other features
>>>> compatible with only a subset of allocators (or more effort spent on the
>>>> features), blocking API improvements (more on that below), and my
>>>> inability to pronounce SLAB and SLUB in a properly distinguishable way,
>>>> without resorting to spelling out the letters.
>>>>
>>>> I think (but may be proven wrong) that SLOB is the easier target of the
>>>> two to be removed, so I'd like to focus on it first.
>>>>
>>>> I believe SLOB can be removed because:
>>>>
>>>> - AFAIK nobody really uses it? It strives for minimal memory footprint
>>>> by putting all objects together, which has its CPU performance costs
>>>> (locking, lack of percpu caching, searching for free space...). I'm not
>>>> aware of any "tiny linux" deployment that opts for this. For example,
>>>> OpenWRT seems to use SLUB and the devices these days have e.g. 128MB
>>>> RAM, not up to 16 MB anymore. I've heard anecdotes that the performance
>>>> SLOB impact is too much for those who tried. Googling for
>>>> "CONFIG_SLOB=y" yielded nothing useful.
>>>
>>> I am all for removing SLOB.
>>>
>>> There are some devices with configs where SLOB is enabled by default.
>>> Perhaps, the owners/maintainers of those devices/configs should be
>>> included into this thread:
>>>
>>> tatashin@soleen:~/x/linux$ git grep SLOB=y
>
>>> arch/riscv/configs/nommu_k210_defconfig:CONFIG_SLOB=y
>>> arch/riscv/configs/nommu_k210_sdcard_defconfig:CONFIG_SLOB=y
>>> arch/riscv/configs/nommu_virt_defconfig:CONFIG_SLOB=y
>
>>
>> Turns out that since SLOB depends on EXPERT, many of those lack it so
>> running make defconfig ends up with SLUB anyway, unless I miss something.
>> Only a subset has both SLOB and EXPERT:
>>
>>> git grep CONFIG_EXPERT `git grep -l "CONFIG_SLOB=y"`
>
>> arch/riscv/configs/nommu_virt_defconfig:CONFIG_EXPERT=y
>
> I suppose there's not really a concern with the virt defconfig, but I
> did check the output of `make nommu_k210_defconfig" and despite not
> having expert it seems to end up CONFIG_SLOB=y in the generated .config.
>
> I do have a board with a k210 so I checked with s/SLOB/SLUB and it still
> boots etc, but I have no workloads or w/e to run on it.
I will try with SLUB over the weekend.
--
Damien Le Moal
Western Digital Research
next prev parent reply other threads:[~2022-11-12 1:41 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <b35c3f82-f67b-2103-7d82-7a7ba7521439@suse.cz>
[not found] ` <CA+CK2bD-uVGJ0=9uc7Lt5zwY+2PM2RTcfOhxEd65S7TvTrJULA@mail.gmail.com>
2022-11-09 9:00 ` Deprecating and removing SLOB Vlastimil Babka
2022-11-09 15:50 ` Aaro Koskinen
2022-11-09 16:45 ` Geert Uytterhoeven
2022-11-09 17:45 ` Mike Rapoport
2022-11-09 21:16 ` Janusz Krzysztofik
2022-11-11 10:33 ` Vlastimil Babka
2022-11-11 20:46 ` Conor Dooley
2022-11-12 1:40 ` Damien Le Moal [this message]
2022-11-14 1:55 ` Damien Le Moal
2022-11-14 5:48 ` Damien Le Moal
2022-11-14 9:36 ` Vlastimil Babka
2022-11-14 11:35 ` Damien Le Moal
2022-11-14 14:47 ` Hyeonggon Yoo
2022-11-15 4:24 ` Damien Le Moal
2022-11-15 4:28 ` Damien Le Moal
2022-11-16 7:57 ` Matthew Wilcox
2022-11-16 8:02 ` Damien Le Moal
2022-11-16 17:51 ` Vlastimil Babka
2022-11-17 0:22 ` Damien Le Moal
2022-11-21 4:30 ` Damien Le Moal
2022-11-21 17:02 ` Vlastimil Babka
2022-11-14 11:50 ` Hyeonggon Yoo
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