linux-kernel - Re: [PATCH] mm, slab: extend kmalloc() alignment for non power-of-two sizes

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Message-ID: <1ca7b081-c1f0-45a3-b901-39c503368f43@suse.cz>
Date: Tue, 2 Jul 2024 22:25:44 +0200
From: Vlastimil Babka <vbabka@...e.cz>
To: Roman Gushchin <roman.gushchin@...ux.dev>
Cc: linux-mm@...ck.org, David Rientjes <rientjes@...gle.com>,
 Christoph Lameter <cl@...ux.com>, Hyeonggon Yoo <42.hyeyoo@...il.com>,
 Kees Cook <keescook@...omium.org>, Alice Ryhl <aliceryhl@...gle.com>,
 Boqun Feng <boqun.feng@...il.com>, rust-for-linux@...r.kernel.org,
 linux-kernel@...r.kernel.org, patches@...ts.linux.dev
Subject: Re: [PATCH] mm, slab: extend kmalloc() alignment for non power-of-two
 sizes

On 7/2/24 9:30 PM, Roman Gushchin wrote:
> On Tue, Jul 02, 2024 at 05:58:01PM +0200, Vlastimil Babka wrote:
> Hello Vlastimil,
> 
> the idea and the implementation makes total sense to me.
> 
> Do you have an estimate for the memory overhead it will typically introduce?

There's no new overhead for the non-debug case as the layout already
naturally has the same alignment as is now guaranteed. Debug has its own
overhead so it's enabled only when needed, and this will not add much more.

> I don't think it will be too large though and actually can be compensated
> by potential performance gains due to a better memory alignment. What do you
> think?

Yeah but again, the difference would be only in the debug case and
performance gains there are not so interesting :)

> Thanks!