linux-kernel - Re: [PATCH 3/4] gcov: add gcov profiling infrastructure

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Message-ID: <20090604090839.GB7030@cr0.nay.redhat.com>
Date:	Thu, 4 Jun 2009 17:08:39 +0800
From:	Amerigo Wang <xiyou.wangcong@...il.com>
To:	Peter Oberparleiter <oberpar@...ux.vnet.ibm.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	linux-kernel@...r.kernel.org, andi@...stfloor.org,
	ying.huang@...el.com, W.Li@....COM, michaele@....ibm.com,
	mingo@...e.hu, heicars2@...ux.vnet.ibm.com,
	mschwid2@...ux.vnet.ibm.com
Subject: Re: [PATCH 3/4] gcov: add gcov profiling infrastructure

On Wed, Jun 03, 2009 at 05:26:22PM +0200, Peter Oberparleiter wrote:
>Peter Oberparleiter wrote:
>> Andrew Morton wrote:
>>> On Tue, 02 Jun 2009 13:44:02 +0200
>>> Peter Oberparleiter <oberpar@...ux.vnet.ibm.com> wrote:
>>>> +	/* Duplicate gcov_info. */
>>>> +	active = num_counter_active(info);
>>>> +	dup = kzalloc(sizeof(struct gcov_info) +
>>>> +		      sizeof(struct gcov_ctr_info) * active, GFP_KERNEL);
>>> 
>>> How large can this allocation be?
>> 
>> Hm, good question. Having a look at my test system, I see coverage data 
>> files of up to 60kb size. With counters making up the largest part of 
>> those, I'd guess the allocation size can be around ~55kb. I assume that 
>> makes it a candidate for vmalloc?
>
>A further run with debug output showed that the maximum size is
>actually around 4k, so in my opinion, there is no need to switch
>to vmalloc.

Unless you want virtually continious memory, you don't need to
bother vmalloc().

kmalloc() and get_free_pages() are all fine for this.
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