linux-kernel - Re: bootmem allocator

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Date:	Tue, 8 Apr 2008 20:18:34 +0400
From:	Cyrill Gorcunov <gorcunov@...il.com>
To:	"H. Peter Anvin" <hpa@...or.com>
Cc:	Yinghai Lu <yhlu.kernel@...il.com>,
	Andi Kleen <andi@...stfloor.org>, Ingo Molnar <mingo@...e.hu>,
	LKML <linux-kernel@...r.kernel.org>
Subject: Re: bootmem allocator

[H. Peter Anvin - Mon, Apr 07, 2008 at 09:33:23PM -0700]
> Cyrill Gorcunov wrote:
>> I think it would be a good idea ;) Btw maybe would be better to call
>> memset on the code witch relies on "clear" memory explicitly? So we will
>> clear memory allocated *only* if we really need this.
>
> Are there any users of bootmem which will allocate a significant amount of 
> memory and don't need it zeroed?
>
> 	-hpa
>

Well, the only really significant allocation I found is in
arch/ia64/kernel/iosapi.c:

---[...]---
static struct iosapic_rte_info * __init_refok iosapic_alloc_rte (void)
{
	int i;
	struct iosapic_rte_info *rte;
	int preallocated = 0;

	if (!iosapic_kmalloc_ok && list_empty(&free_rte_list)) {
--->		rte = alloc_bootmem(sizeof(struct iosapic_rte_info) *
				    NR_PREALLOCATE_RTE_ENTRIES);
		if (!rte)
			return NULL;
		for (i = 0; i < NR_PREALLOCATE_RTE_ENTRIES; i++, rte++)
			list_add(&rte->rte_list, &free_rte_list);
	}

	if (!list_empty(&free_rte_list)) {
		rte = list_entry(free_rte_list.next, struct iosapic_rte_info,
				 rte_list);
		list_del(&rte->rte_list);
		preallocated++;
	} else {
		rte = kmalloc(sizeof(struct iosapic_rte_info), GFP_ATOMIC);
		if (!rte)
			return NULL;
	}

	memset(rte, 0, sizeof(struct iosapic_rte_info));
	if (preallocated)
		rte->flags |= RTE_PREALLOCATED;

	return rte;
}
---[...]---

but it requires zeroed memory too. So, no, I didn't found any large
number of bytes allocated by bootmem scheme without needing of its
clearing.

		- Cyrill -
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