From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1760872AbYEMV1M (ORCPT ); Tue, 13 May 2008 17:27:12 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756333AbYEMV06 (ORCPT ); Tue, 13 May 2008 17:26:58 -0400 Received: from de01egw01.freescale.net ([192.88.165.102]:62199 "EHLO de01egw01.freescale.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755650AbYEMV05 (ORCPT ); Tue, 13 May 2008 17:26:57 -0400 From: Timur Tabi To: andi@firstfloor.org, linux-kernel@vger.kernel.org Subject: [PATCH][RFC] Add alloc_pages_exact() and free_pages_exact() Date: Tue, 13 May 2008 16:26:46 -0500 Message-Id: <1210714006-8976-1-git-send-email-timur@freescale.com> X-Mailer: git-send-email 1.5.5 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org alloc_pages_exact() is similar to alloc_pages(), except that it allocates the minimum number of pages to fulfill the request. This is useful if you want to allocate a very large buffer that is slightly larger than an even power-of-two number of pages. In that case, alloc_pages() will waste a lot of memory. I have a video driver that wants to allocate a 5MB buffer. alloc_pages() will waste 3MB of physically-contiguous memory. Therefore, I would like to see alloc_pages_exact() added to 2.6.27. Please note that I am not a Linux VM expert. I wrote these functions based on guidance from Andi Kleen. I have no familiarity with NUMA, so I don't know how to handle that. Any and all suggestions are welcome. Signed-off-by: Timur Tabi --- include/linux/gfp.h | 3 ++ mm/page_alloc.c | 53 +++++++++++++++++++++++++++++++++++++++++++++++++++ 2 files changed, 56 insertions(+), 0 deletions(-) diff --git a/include/linux/gfp.h b/include/linux/gfp.h index b414be3..1054801 100644 --- a/include/linux/gfp.h +++ b/include/linux/gfp.h @@ -215,6 +215,9 @@ extern struct page *alloc_page_vma(gfp_t gfp_mask, extern unsigned long __get_free_pages(gfp_t gfp_mask, unsigned int order); extern unsigned long get_zeroed_page(gfp_t gfp_mask); +void *alloc_pages_exact(size_t size, gfp_t gfp_mask); +void free_pages_exact(void *virt, size_t size); + #define __get_free_page(gfp_mask) \ __get_free_pages((gfp_mask),0) diff --git a/mm/page_alloc.c b/mm/page_alloc.c index bdd5c43..2b685eb 100644 --- a/mm/page_alloc.c +++ b/mm/page_alloc.c @@ -1736,6 +1736,59 @@ void free_pages(unsigned long addr, unsigned int order) EXPORT_SYMBOL(free_pages); +/** + * Allocate an exact number of pages of physically-contiguous memory. + * + * This function is similar to alloc_pages(), except that it allocates the + * minimum number of pages to satisfy the request. alloc_pages() can only + * allocate memory in power-of-two pages. + * + * This function is also limited by MAX_ORDER. + * + * Memory allocated by this function must be released by free_pages_exact(). + */ +void *alloc_pages_exact(size_t size, gfp_t gfp_mask) +{ + unsigned int order = get_order(size); + unsigned long addr; + + addr = __get_free_pages(gfp_mask, order); + if (addr) { + unsigned long alloc_end = addr + (PAGE_SIZE << order); + unsigned long used = addr + PAGE_ALIGN(size); + + split_page(virt_to_page(addr), order); + while (used < alloc_end) { + free_page(used); + used += PAGE_SIZE; + } + } + + return (void *)addr; +} +EXPORT_SYMBOL(alloc_pages_exact); + +/** + * Releases memory allocated via alloc_pages_exact() + * + * Release the memory allocated by a previous call to alloc_pages_exact. + * + * The first parameter must be the value returned by alloc_pages_exact(), + * and the 'size' parameter must be the same as was passed to + * alloc_pages_exact(). + */ +void free_pages_exact(void *virt, size_t size) +{ + unsigned long addr = (unsigned long)virt; + unsigned long end = addr + PAGE_ALIGN(size); + + while (addr < end) { + free_page(addr); + addr += PAGE_SIZE; + } +} +EXPORT_SYMBOL(free_pages_exact); + static unsigned int nr_free_zone_pages(int offset) { struct zoneref *z; -- 1.5.5