From: Hyeonggon Yoo <42.hyeyoo@gmail.com>
To: Vlastimil Babka <vbabka@suse.cz>
Cc: Rustam Kovhaev <rkovhaev@gmail.com>,
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: Sun, 24 Oct 2021 10:43:40 +0000 [thread overview]
Message-ID: <20211024104340.GA4370@kvm.asia-northeast3-a.c.our-ratio-313919.internal> (raw)
In-Reply-To: <1dfb7a79-3e66-a9fe-ee7c-1277d7ff5950@suse.cz>
On Thu, Oct 21, 2021 at 07:36:26PM +0200, Vlastimil Babka wrote:
> On 10/20/21 13:46, Hyeonggon Yoo wrote:
> > On Sun, Oct 17, 2021 at 08:38:41PM -0700, 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).
> >
> > Hello Rustam, I measured its impact on memory usage on
> > tiny kernel configuration as SLOB is used in very small machine.
> >
> > on x86 32 bit + tinyconfig:
> > Before:
> > Slab: 668 kB
> >
> > After:
> > Slab: 688~692 kB
> >
> > it adds 20~24kB.
>
> Thanks for the measurement. That's 3.5% increase.
>
You're welcome.
> >
> >>
> >> The main reason for this change is to simplify SLOB a little bit, make
> >> it a bit easier to debug whenever something goes wrong.
> >>
> >
> > It seems acceptable But I wonder it is worth to increase memory usage
> > to allow freeing kmem_cache_alloc-ed objects by kfree()?
>
> Not for the reason above, but for providing a useful API guarantee
> regardless of selected slab allocator IMHO yes.
>
Mm.. that means some callers free kmem_cache_alloc-ed object using
kfree, and SLAB/SLUB already support that, and SLOB doesn't.
In what situations is freeing using kfree needed?
Wouldn't this make code confusing?
> > Thanks,
> > Hyeonggon
> >
> >> meminfo right after the system boot, without the patch:
> >> Slab: 35500 kB
> >>
> >> the same, with the patch:
> >> Slab: 36396 kB
> >>
> >
>
next prev parent reply other threads:[~2021-10-24 10:43 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
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 ` Hyeonggon Yoo [this message]
2021-10-25 8:19 ` [PATCH] " Vlastimil Babka
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