linux-kernel - RE: Do we still need SLAB_MEM_SPREAD (and possibly others)?

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Date: Tue, 6 Feb 2024 01:46:42 +0000
From: "Song, Xiongwei" <Xiongwei.Song@...driver.com>
To: "Christoph Lameter (Ampere)" <cl@...ux.com>,
        Waiman Long
	<longman@...hat.com>, Zefan Li <lizefan.x@...edance.com>
CC: Chengming Zhou <chengming.zhou@...ux.dev>,
        Vlastimil Babka
	<vbabka@...e.cz>, Yosry Ahmed <yosryahmed@...gle.com>,
        Steven Rostedt
	<rostedt@...dmis.org>,
        LKML <linux-kernel@...r.kernel.org>,
        "linux-mm@...ck.org" <linux-mm@...ck.org>,
        Andrew Morton
	<akpm@...ux-foundation.org>,
        Linus Torvalds <torvalds@...ux-foundation.org>,
        Kees Cook <keescook@...omium.org>,
        David Rientjes <rientjes@...gle.com>,
        Hyeonggon Yoo <42.hyeyoo@...il.com>,
        Chengming Zhou
	<zhouchengming@...edance.com>,
        Zheng Yejian <zhengyejian1@...wei.com>,
        "cgroups@...r.kernel.org" <cgroups@...r.kernel.org>
Subject: RE: Do we still need SLAB_MEM_SPREAD (and possibly others)?

Adding the maintainers of cpuset of cgroup.

> 
> On Sun, 4 Feb 2024, Song, Xiongwei wrote:
> 
> > Once SLAB_MEM_SPREAD is removed, IMO, cpuset.memory_spread_slab is useless.
> 
> SLAB_MEM_SPREAD does not do anything anymore. SLUB relies on the
> "spreading" via the page allocator memory policies instead of doing its
> own like SLAB used to do.
> 
> What does FILE_SPREAD_SLAB do? Dont see anything there either.

The FILE_SPREAD_SLAB flag is used by cpuset.memory_spread_slab with read/write operations:

In kernel/cgroup/cpuset.c, 
static struct cftype legacy_files[] = {
.. snip ...
        {
                .name = "memory_spread_slab",
                .read_u64 = cpuset_read_u64,
                .write_u64 = cpuset_write_u64,
                .private = FILE_SPREAD_SLAB,
        },
.. snip ...
};

Regards,
Xiongwei