linux-ext4 - Re: [PATCH 1/9] mm: add generic adaptive large memory allocationAPIs

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Message-Id: <20100517103050.21B6.A69D9226@jp.fujitsu.com>
Date:	Mon, 17 May 2010 10:34:30 +0900 (JST)
From:	KOSAKI Motohiro <kosaki.motohiro@...fujitsu.com>
To:	Tetsuo Handa <penguin-kernel@...ove.SAKURA.ne.jp>
Cc:	kosaki.motohiro@...fujitsu.com, peterz@...radead.org,
	xiaosuo@...il.com, akpm@...ux-foundation.org, hnguyen@...ibm.com,
	raisch@...ibm.com, rolandd@...co.com, sean.hefty@...el.com,
	hal.rosenstock@...il.com, divy@...lsio.com,
	James.Bottomley@...e.de, tytso@....edu, adilger@....com,
	viro@...iv.linux.org.uk, menage@...gle.com, lizf@...fujitsu.com,
	linux-rdma@...r.kernel.org, linux-kernel@...r.kernel.org,
	netdev@...r.kernel.org, linux-scsi@...r.kernel.org,
	linux-ext4@...r.kernel.org, linux-fsdevel@...r.kernel.org,
	linux-mm@...ck.org, containers@...ts.linux-foundation.org,
	eric.dumazet@...il.com
Subject: Re: [PATCH 1/9] mm: add generic adaptive large memory allocationAPIs

> Peter Zijlstra wrote:
> > NAK, I really utterly dislike that inatomic argument. The alloc side
> > doesn't function in atomic context either. Please keep the thing
> > symmetric in that regards.
> 
> Excuse me. kmalloc(GFP_KERNEL) may sleep (and therefore cannot be used in
> atomic context). However, kfree() for memory allocated with kmalloc(GFP_KERNEL)
> never sleep (and therefore can be used in atomic context).
> Why kmalloc() and kfree() are NOT kept symmetric?

In kmalloc case, we need to consider both kmalloc(GFP_KERNEL)/kfree() pair and
kmalloc(GFP_ATOMIC)/kfree() pair. latter is mainly used on atomic context.
To make kfree() atomic help to keep the implementation simple.

But kvmalloc don't have GFP_ATOMIC feautre. that's big difference.



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