From: Harry Yoo <harry.yoo@oracle.com>
To: "Christoph Lameter (Ampere)" <cl@gentwo.org>
Cc: Vlastimil Babka <vbabka@suse.cz>,
David Rientjes <rientjes@google.com>,
Andrew Morton <akpm@linux-foundation.org>,
Johannes Weiner <hannes@cmpxchg.org>,
Michal Hocko <mhocko@kernel.org>,
Roman Gushchin <roman.gushchin@linux.dev>,
Shakeel Butt <shakeel.butt@linux.dev>,
Muchun Song <muchun.song@linux.dev>,
Suren Baghdasaryan <surenb@google.com>,
Kent Overstreet <kent.overstreet@linux.dev>,
Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Alexander Potapenko <glider@google.com>,
Andrey Konovalov <andreyknvl@gmail.com>,
Dmitry Vyukov <dvyukov@google.com>,
Vincenzo Frascino <vincenzo.frascino@arm.com>,
linux-mm@kvack.org
Subject: Re: [RFC PATCH] mm/slab: save memory by allocating slabobj_ext array from leftover
Date: Mon, 16 Jun 2025 20:00:06 +0900 [thread overview]
Message-ID: <aE_5Nu2cC6IdCPLM@hyeyoo> (raw)
In-Reply-To: <aExkJhM_P8mnLC12@hyeyoo>
On Sat, Jun 14, 2025 at 02:47:18AM +0900, Harry Yoo wrote:
> On Fri, Jun 13, 2025 at 09:04:34AM -0700, Christoph Lameter (Ampere) wrote:
> > On Fri, 13 Jun 2025, Harry Yoo wrote:
> >
> > > Allocate slabobj_exts array from this unused space instead of using
> > > kcalloc(), when it is large enough.
> >
> > How does slab debug work in this case? The object layout gets a bit
> > complicated with other metadata there as well.
>
> Oh, the 'leftover' space I mentioned the cover letter refers to the
> wasted space after the last object in a slab, not unused bytes within
> objects.
>
> There is no per-object metadata stored there and SLUB simply poisons the area.
> I taught slab_pad_check() to skip checking the slabobj_exts array.
Actually, it might be worth considering placing it within object in case
the object is exactly a power-of-two size but has some wasted bytes
due to alignment.
xfs_inode seems to be a good candidate that could benefit from this.
Hopefully it doesn't introduce too much complexity...
--
Cheers,
Harry / Hyeonggon
next prev parent reply other threads:[~2025-06-16 11:00 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2025-06-13 6:33 Harry Yoo
2025-06-13 7:11 ` Harry Yoo
2025-06-13 11:42 ` Yeoreum Yun
2025-06-13 17:58 ` Harry Yoo
2025-06-13 16:04 ` Christoph Lameter (Ampere)
2025-06-13 17:47 ` Harry Yoo
2025-06-16 11:00 ` Harry Yoo [this message]
2025-06-19 7:56 ` Vlastimil Babka
2025-08-05 11:57 ` Harry Yoo
2025-08-08 14:44 ` Vlastimil Babka
2025-08-27 11:40 ` Harry Yoo
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