From: Tejun Heo <tj@kernel.org>
To: Lai Jiangshan <laijs@cn.fujitsu.com>
Cc: linux-kernel@vger.kernel.org,
Andrew Morton <akpm@linux-foundation.org>,
Vladimir Davydov <vdavydov@parallels.com>,
Jiri Kosina <jkosina@suse.cz>, Jeff Layton <jlayton@redhat.com>,
Andreas Gruenbacher <agruen@linbit.com>,
Stephen Hemminger <stephen@networkplumber.org>,
Jean Delvare <jdelvare@suse.de>,
Monam Agarwal <monamagarwal123@gmail.com>
Subject: Re: [PATCH 3/4] ida: in-place ida allocation
Date: Tue, 22 Apr 2014 16:02:21 -0400 [thread overview]
Message-ID: <20140422200221.GC2314@mtj.dyndns.org> (raw)
In-Reply-To: <1398161781-12105-4-git-send-email-laijs@cn.fujitsu.com>
On Tue, Apr 22, 2014 at 06:16:20PM +0800, Lai Jiangshan wrote:
> There are two stages of ida allocation/free, idr_layers and ida_bitmap.
> They add unneeded foot print and memory waste.
>
> When a single ID is first allocated from an ida, this ida requires
> two big chunks of memory. One idr_layer and one ida_bitmap.
>
> To reduce the foot print and memory, we reduce the ida_bitmap
> to a single "unsigned long" and place it in its own idr-slot
> and avoid to allocate the ida_bitmap.
>
> It also means ida bitmap is located on its coresponding idr-slot
> which size is the same as "unsigned long".
> Each ida bitmap(idr-slot) contains BITS_PER_LONG ida-slots.
>
> The struct ida_bitmap is not needed any more, we use "unsigned long"
> directly and remove all the code of alloc/free struct ida_bitmap.
Are you calling 128 byte a "big chunk of memory" while trading off
tree depth for it? No, this level of space optimizaiton is completely
uncalled for.
Nacked-by: Tejun Heo <tj@kernel.org>
Thanks.
--
tejun
next prev parent reply other threads:[~2014-04-22 20:02 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2014-04-22 10:16 [PATCH 0/4] idr: idr cleanups Lai Jiangshan
2014-04-22 10:16 ` [PATCH 1/4] idr: proper invalid argument handling Lai Jiangshan
2014-04-22 19:16 ` Andrew Morton
2014-04-22 19:46 ` Andrew Morton
2014-04-22 19:54 ` Tejun Heo
2014-04-22 10:16 ` [PATCH 2/4] idr: reduce the number of MAX_IDR_FREE Lai Jiangshan
2014-04-22 19:58 ` Tejun Heo
2014-04-23 1:55 ` Lai Jiangshan
2014-04-22 10:16 ` [PATCH 3/4] ida: in-place ida allocation Lai Jiangshan
2014-04-22 20:02 ` Tejun Heo [this message]
2014-04-23 1:44 ` Lai Jiangshan
2014-04-22 10:16 ` [PATCH 4/4] idr: reorder the fields Lai Jiangshan
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