linux-kernel.vger.kernel.org archive mirror
 help / color / mirror / Atom feed
From: Vlastimil Babka <vbabka@suse.cz>
To: Hyeonggon Yoo <42.hyeyoo@gmail.com>, Rustam Kovhaev <rkovhaev@gmail.com>
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: Thu, 21 Oct 2021 19:36:26 +0200	[thread overview]
Message-ID: <1dfb7a79-3e66-a9fe-ee7c-1277d7ff5950@suse.cz> (raw)
In-Reply-To: <20211020114638.GA378758@kvm.asia-northeast3-a.c.our-ratio-313919.internal>

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.

> 
>> 
>> 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.

> Thanks,
> Hyeonggon
> 
>> meminfo right after the system boot, without the patch:
>> Slab:              35500 kB
>> 
>> the same, with the patch:
>> Slab:              36396 kB
>> 
> 


  reply	other threads:[~2021-10-21 17:36 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 [this message]
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

Reply instructions:

You may reply publicly to this message via plain-text email
using any one of the following methods:

* Save the following mbox file, import it into your mail client,
  and reply-to-all from there: mbox

  Avoid top-posting and favor interleaved quoting:
  https://en.wikipedia.org/wiki/Posting_style#Interleaved_style

* Reply using the --to, --cc, and --in-reply-to
  switches of git-send-email(1):

  git send-email \
    --in-reply-to=1dfb7a79-3e66-a9fe-ee7c-1277d7ff5950@suse.cz \
    --to=vbabka@suse.cz \
    --cc=42.hyeyoo@gmail.com \
    --cc=akpm@linux-foundation.org \
    --cc=cl@linux.com \
    --cc=david@fromorbit.com \
    --cc=djwong@kernel.org \
    --cc=dvyukov@google.com \
    --cc=gregkh@linuxfoundation.org \
    --cc=iamjoonsoo.kim@lge.com \
    --cc=linux-kernel@vger.kernel.org \
    --cc=linux-mm@kvack.org \
    --cc=penberg@kernel.org \
    --cc=rientjes@google.com \
    --cc=rkovhaev@gmail.com \
    --cc=viro@zeniv.linux.org.uk \
    /path/to/YOUR_REPLY

  https://kernel.org/pub/software/scm/git/docs/git-send-email.html

* If your mail client supports setting the In-Reply-To header
  via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line before the message body. 
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).