From: Rustam Kovhaev <rkovhaev@gmail.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: cl@linux.com, penberg@kernel.org, rientjes@google.com,
iamjoonsoo.kim@lge.com, akpm@linux-foundation.org,
djwong@kernel.org, david@fromorbit.com,
linux-kernel@vger.kernel.org, linux-mm@kvack.org,
gregkh@linuxfoundation.org, viro@zeniv.linux.org.uk,
dvyukov@google.com
Subject: Re: [PATCH] slob: add size header to all allocations
Date: Mon, 18 Oct 2021 18:22:28 -0700 [thread overview]
Message-ID: <YW4d1FppmaqAuPHd@nuc10> (raw)
In-Reply-To: <20758764-8139-ab0b-a782-dc63559b43ba@suse.cz>
On Mon, Oct 18, 2021 at 11:22:46AM +0200, Vlastimil Babka wrote:
> On 10/18/21 05:38, Rustam Kovhaev wrote:
> > Let's prepend all allocations of (PAGE_SIZE - align_offset) and less
> > with the size header. This way kmem_cache_alloc() memory can be freed
> > with kfree() and the other way around, as long as they are less than
> > (PAGE_SIZE - align_offset).
>
> This size limitation seems like an unnecessary gotcha. Couldn't we make
> these large allocations in slob_alloc_node() (that use slob_new_pages()
> directly) similar enough to large kmalloc() ones, so that kfree() can
> recognize them and free properly? AFAICS it might mean just adding
> __GFP_COMP to make sure there's a compound order stored, as these already
> don't seem to set PageSlab.
Thanks for the pointers, I'll send a new version.
> > The main reason for this change is to simplify SLOB a little bit, make
> > it a bit easier to debug whenever something goes wrong.
>
> I would say the main reason is to simplify the slab API and guarantee that
> both kmem_cache_alloc() and kmalloc() can be freed by kfree().
>
> We should also update the comments at top of slob.c to reflect the change.
> And Documentation/core-api/memory-allocation.rst (the last paragraph).
OK, thank you!
> > meminfo right after the system boot, without the patch:
> > Slab: 35500 kB
> >
> > the same, with the patch:
> > Slab: 36396 kB
>
> 2.5% increase, hopefully acceptable.
>
> Thanks!
next prev parent reply other threads:[~2021-10-19 1:22 UTC|newest]
Thread overview: 42+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-29 21:23 [PATCH] xfs: use kmem_cache_free() for kmem_cache objects Rustam Kovhaev
2021-09-30 4:42 ` Dave Chinner
2021-09-30 8:13 ` Vlastimil Babka
2021-09-30 18:48 ` Rustam Kovhaev
2021-09-30 21:10 ` Vlastimil Babka
2021-10-01 0:32 ` Rustam Kovhaev
2021-10-04 1:07 ` David Rientjes
2021-10-12 20:43 ` Darrick J. Wong
2021-10-12 20:43 ` Darrick J. Wong
2021-10-12 21:32 ` Vlastimil Babka
2021-10-12 23:22 ` Darrick J. Wong
2021-10-13 7:38 ` Vlastimil Babka
2021-10-13 16:56 ` Rustam Kovhaev
2021-10-15 0:57 ` Darrick J. Wong
2021-10-18 3:38 ` [PATCH] slob: add size header to all allocations Rustam Kovhaev
2021-10-18 9:22 ` Vlastimil Babka
2021-10-19 1:22 ` Rustam Kovhaev [this message]
2021-10-20 11:46 ` Hyeonggon Yoo
2021-10-21 17:36 ` Vlastimil Babka
2021-10-23 6:41 ` [PATCH v2] " Rustam Kovhaev
2021-10-25 9:36 ` Vlastimil Babka
2021-10-25 21:49 ` Rustam Kovhaev
2021-10-29 3:05 ` [PATCH v3] " Rustam Kovhaev
2021-11-16 11:26 ` Vlastimil Babka
2021-11-16 23:19 ` Rustam Kovhaev
2021-11-22 1:30 ` [PATCH v4] " Rustam Kovhaev
2021-11-22 9:22 ` Christoph Lameter
2021-11-22 9:40 ` Vlastimil Babka
2021-11-22 10:36 ` Christoph Lameter
2021-11-22 10:45 ` Vlastimil Babka
2021-11-22 11:40 ` Christoph Lameter
2021-11-22 11:49 ` Vlastimil Babka
2021-11-23 10:18 ` David Laight
2021-11-30 7:00 ` Rustam Kovhaev
2021-11-30 9:23 ` David Laight
2021-11-30 9:41 ` Christoph Lameter
2021-11-30 14:55 ` Vlastimil Babka
2021-11-30 15:21 ` David Laight
2021-11-30 15:39 ` Vlastimil Babka
2021-11-30 15:26 ` Christoph Lameter
2021-10-24 10:43 ` [PATCH] " Hyeonggon Yoo
2021-10-25 8:19 ` Vlastimil Babka
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