From: Andrew Morton <akpm@linux-foundation.org>
To: Andrzej Hajda <a.hajda@samsung.com>
Cc: linux-mm@kvack.org, Marek Szyprowski <m.szyprowski@samsung.com>,
Kyungmin Park <kyungmin.park@samsung.com>,
linux-kernel@vger.kernel.org, andi@firstfloor.org, andi@lisas.de,
Mike Turquette <mturquette@linaro.org>,
Alexander Viro <viro@zeniv.linux.org.uk>,
Tejun Heo <tj@kernel.org>
Subject: Re: [PATCH 0/5] kstrdup optimization
Date: Tue, 13 Jan 2015 15:37:31 -0800 [thread overview]
Message-ID: <20150113153731.43eefac721964d165396e5af@linux-foundation.org> (raw)
In-Reply-To: <1421054323-14430-1-git-send-email-a.hajda@samsung.com>
On Mon, 12 Jan 2015 10:18:38 +0100 Andrzej Hajda <a.hajda@samsung.com> wrote:
> Hi,
>
> kstrdup if often used to duplicate strings where neither source neither
> destination will be ever modified. In such case we can just reuse the source
> instead of duplicating it. The problem is that we must be sure that
> the source is non-modifiable and its life-time is long enough.
>
> I suspect the good candidates for such strings are strings located in kernel
> .rodata section, they cannot be modifed because the section is read-only and
> their life-time is equal to kernel life-time.
>
> This small patchset proposes alternative version of kstrdup - kstrdup_const,
> which returns source string if it is located in .rodata otherwise it fallbacks
> to kstrdup.
> To verify if the source is in .rodata function checks if the address is between
> sentinels __start_rodata, __end_rodata. I guess it should work with all
> architectures.
>
> The main patch is accompanied by four patches constifying kstrdup for cases
> where situtation described above happens frequently.
>
> As I have tested the patchset on mobile platform (exynos4210-trats) it saves
> 3272 string allocations. Since minimal allocation is 32 or 64 bytes depending
> on Kconfig options the patchset saves respectively about 100KB or 200KB of memory.
That's a lot of memory. I wonder where it's all going to. sysfs,
probably?
What the heck does (the cheerily undocumented) KERNFS_STATIC_NAME do
and can we remove it if this patchset is in place?
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2015-01-13 23:37 UTC|newest]
Thread overview: 18+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-01-12 9:18 Andrzej Hajda
2015-01-12 9:18 ` [PATCH 1/5] mm/util: add kstrdup_const Andrzej Hajda
2015-01-12 17:13 ` Joe Perches
2015-01-12 9:18 ` [PATCH 2/5] kernfs: convert node name allocation to kstrdup_const Andrzej Hajda
2015-01-14 14:13 ` Tejun Heo
2015-01-14 14:37 ` [PATCH 2.5/5] kernfs: remove KERNFS_STATIC_NAME Tejun Heo
2015-01-12 9:18 ` [PATCH 3/5] clk: convert clock name allocations to kstrdup_const Andrzej Hajda
2015-01-12 23:11 ` Mike Turquette
2015-01-13 7:57 ` Andrzej Hajda
2015-01-12 9:18 ` [PATCH 4/5] mm/slab: convert cache " Andrzej Hajda
2015-01-12 9:18 ` [PATCH 5/5] fs/namespace: convert devname allocation " Andrzej Hajda
2015-01-12 20:45 ` [PATCH 0/5] kstrdup optimization Geert Uytterhoeven
2015-01-13 23:48 ` Andrew Morton
2015-01-14 0:10 ` Craig Milo Rogers
2015-01-14 0:17 ` Andrew Morton
2015-01-13 23:37 ` Andrew Morton [this message]
2015-01-14 8:06 ` Andrzej Hajda
2015-01-14 14:12 ` Tejun Heo
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=20150113153731.43eefac721964d165396e5af@linux-foundation.org \
--to=akpm@linux-foundation.org \
--cc=a.hajda@samsung.com \
--cc=andi@firstfloor.org \
--cc=andi@lisas.de \
--cc=kyungmin.park@samsung.com \
--cc=linux-kernel@vger.kernel.org \
--cc=linux-mm@kvack.org \
--cc=m.szyprowski@samsung.com \
--cc=mturquette@linaro.org \
--cc=tj@kernel.org \
--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