linux-kernel - Re: [RFC] mm: generic adaptive large memory allocation APIs

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Message-Id: <20100513191838.217F.A69D9226@jp.fujitsu.com>
Date:	Thu, 13 May 2010 19:43:49 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Jiri Slaby <jslaby@...e.cz>
Cc:	kosaki.motohiro@...fujitsu.com, Changli Gao <xiaosuo@...il.com>,
	akpm@...ux-foundation.org, Eric Dumazet <eric.dumazet@...il.com>,
	Alexander Viro <viro@...iv.linux.org.uk>,
	"Paul E. McKenney" <paulmck@...ux.vnet.ibm.com>,
	Alexey Dobriyan <adobriyan@...il.com>,
	Ingo Molnar <mingo@...e.hu>,
	Peter Zijlstra <peterz@...radead.org>,
	linux-fsdevel@...r.kernel.org, linux-kernel@...r.kernel.org,
	Avi Kivity <avi@...hat.com>,
	Tetsuo Handa <penguin-kernel@...ove.sakura.ne.jp>
Subject: Re: [RFC] mm: generic adaptive large memory allocation APIs

> On 05/13/2010 11:40 AM, KOSAKI Motohiro wrote:
> >>>> Anyway as this is a replacement for explicit tests, it shouldn't change
> >>>> the behaviour in any way. Obviously when a user doesn't need virtually
> >>>> contiguous space, he shouldn't use this interface at all.
> >>>
> >>> Why can't we make fdtable virtually contiguous free?
> >>
> >> This is possible, but the question is why to make the code more complex?
> > 
> > because  it's broken.
> 
> Well, could you explain what exactly is broken about
> x = kmalloc(size, GFP_KERNEL);
> if (!x)
>   x = vmalloc(size);
> ? Is is that kmalloc doesn't return until is has the memory to return
> when asking for order(size) <= COSTLY_ORDER? I think this is expected.

Well, but fdtable doesn't really need contenious memory. no?
To make API mean we recommend to use it. but I don't hope to spread this 
wrong habit.  Instead, to kill it seems better.



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