linux-kernel - Re: [RFC PATCH V3 6/7] mm/slab: save memory by allocating slabobj

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <aQK7KaxX17goz926@hyeyoo>
Date: Thu, 30 Oct 2025 10:11:05 +0900
From: Harry Yoo <harry.yoo@...cle.com>
To: Andrey Ryabinin <ryabinin.a.a@...il.com>
Cc: akpm@...ux-foundation.org, vbabka@...e.cz, andreyknvl@...il.com,
        cl@...ux.com, dvyukov@...gle.com, glider@...gle.com,
        hannes@...xchg.org, linux-mm@...ck.org, mhocko@...nel.org,
        muchun.song@...ux.dev, rientjes@...gle.com, roman.gushchin@...ux.dev,
        shakeel.butt@...ux.dev, surenb@...gle.com, vincenzo.frascino@....com,
        yeoreum.yun@....com, tytso@....edu, adilger.kernel@...ger.ca,
        linux-ext4@...r.kernel.org, linux-kernel@...r.kernel.org
Subject: Re: [RFC PATCH V3 6/7] mm/slab: save memory by allocating
 slabobj_ext array from leftover

On Wed, Oct 29, 2025 at 07:45:32PM +0100, Andrey Ryabinin wrote:
> 
> 
> On 10/27/25 1:28 PM, Harry Yoo wrote:
> 
> >  
> > +#ifdef CONFIG_SLAB_OBJ_EXT
> > +
> > +/*
> > + * Check if memory cgroup or memory allocation profiling is enabled.
> > + * If enabled, SLUB tries to reduce memory overhead of accounting
> > + * slab objects. If neither is enabled when this function is called,
> > + * the optimization is simply skipped to avoid affecting caches that do not
> > + * need slabobj_ext metadata.
> > + *
> > + * However, this may disable optimization when memory cgroup or memory
> > + * allocation profiling is used, but slabs are created too early
> > + * even before those subsystems are initialized.
> > + */
> > +static inline bool need_slab_obj_exts(struct kmem_cache *s)
> > +{
> > +	if (!mem_cgroup_disabled() && (s->flags & SLAB_ACCOUNT))
> 
> Shouldn't this be !memcg_kmem_online() check?
> In case of disabled kmem accounting via 'cgroup.memory=nokmem'

Good catch. Will fix, thanks!

> > +		return true;
> > +
> > +	if (mem_alloc_profiling_enabled())
> > +		return true;
> > +
> > +	return false;
> > +}
> > +

-- 
Cheers,
Harry / Hyeonggon