From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail143.messagelabs.com (mail143.messagelabs.com [216.82.254.35]) by kanga.kvack.org (Postfix) with ESMTP id ABA506B0047 for ; Thu, 1 Dec 2011 17:11:05 -0500 (EST) From: =?UTF-8?q?Uwe=20Kleine-K=C3=B6nig?= Subject: [PATCH RFC] bootmem: micro optimize freeing pages in bulks Date: Thu, 1 Dec 2011 23:10:55 +0100 Message-Id: <1322777455-32315-1-git-send-email-u.kleine-koenig@pengutronix.de> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8bit Sender: owner-linux-mm@kvack.org List-ID: To: linux-kernel@vger.kernel.org, linux-mm@kvack.org Cc: Johannes Weiner , Andrew Morton The first entry of bdata->node_bootmem_map holds the data for bdata->node_min_pfn up to bdata->node_min_pfn + BITS_PER_LONG - 1. So the test for freeing all pages of a single map entry can be slightly relaxed. Moreover use DIV_ROUND_UP in another place instead of open coding it. Cc: Johannes Weiner Cc: Andrew Morton Signed-off-by: Uwe Kleine-KA?nig --- Hello, I'm not sure the current code is correct (and my patch doesn't fix it): If aligned && vec == ~0UL evalutates to true, but start + BITS_PER_LONG <= end does not (or "< end" resp.) the else branch still frees all BITS_PER_LONG pages. Is this intended? If yes, the last check can better be omitted resulting in the pages being freed in a bulk. If not, the loop in the else branch should only do something like: while (vec && off < min(BITS_PER_LONG, end - start)) { ... Having said that please note that I just started today to look into mm/ so please take my analysis with a grain of salt. Best regards Uwe mm/bootmem.c | 4 ++-- 1 files changed, 2 insertions(+), 2 deletions(-) diff --git a/mm/bootmem.c b/mm/bootmem.c index fc22150..1e7d791 100644 --- a/mm/bootmem.c +++ b/mm/bootmem.c @@ -56,7 +56,7 @@ early_param("bootmem_debug", bootmem_debug_setup); static unsigned long __init bootmap_bytes(unsigned long pages) { - unsigned long bytes = (pages + 7) / 8; + unsigned long bytes = DIV_ROUND_UP(pages, 8); return ALIGN(bytes, sizeof(long)); } @@ -197,7 +197,7 @@ static unsigned long __init free_all_bootmem_core(bootmem_data_t *bdata) idx = start - bdata->node_min_pfn; vec = ~map[idx / BITS_PER_LONG]; - if (aligned && vec == ~0UL && start + BITS_PER_LONG < end) { + if (aligned && vec == ~0UL && start + BITS_PER_LONG <= end) { int order = ilog2(BITS_PER_LONG); __free_pages_bootmem(pfn_to_page(start), order); -- 1.7.7.1 -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Fight unfair telecom internet charges in Canada: sign http://stopthemeter.ca/ Don't email: email@kvack.org