From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pa0-f54.google.com (mail-pa0-f54.google.com [209.85.220.54]) by kanga.kvack.org (Postfix) with ESMTP id 94447680DC6 for ; Sat, 3 Oct 2015 08:57:44 -0400 (EDT) Received: by pacfv12 with SMTP id fv12so134197193pac.2 for ; Sat, 03 Oct 2015 05:57:44 -0700 (PDT) Received: from smtprelay.synopsys.com (us01smtprelay-2.synopsys.com. [198.182.47.9]) by mx.google.com with ESMTPS id hd5si24461581pbb.257.2015.10.03.05.57.43 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Sat, 03 Oct 2015 05:57:43 -0700 (PDT) From: Vineet Gupta Subject: New helper to free highmem pages in larger chunks Message-ID: <560FD031.3030909@synopsys.com> Date: Sat, 3 Oct 2015 18:25:13 +0530 MIME-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Sender: owner-linux-mm@kvack.org List-ID: To: Andrew Morton , Robin Holt , Nathan Zimmer Cc: Jiang Liu , "linux-mm@kvack.org" , "linux-arch@vger.kernel.org" , lkml , Mel Gorman Hi, I noticed increased boot time when enabling highmem for ARC. Turns out that freeing highmem pages into buddy allocator is done page at a time, while it is batched for low mem pages. Below is call flow. I'm thinking of writing free_highmem_pages() which takes start and end pfn and want to solicit some ideas whether to write it from scratch or preferably call existing __free_pages_memory() to reuse the logic to convert a pfn range into {pfn, order} tuples. For latter however there are semantical differences as you can see below which I'm not sure of: -highmem page->count is set to 1, while 0 for low mem -atomic clearing of page reserved flag vs. non atomic mem_init for (tmp = min_high_pfn; tmp < max_pfn; tmp++) free_highmem_page(pfn_to_page(tmp)); __free_reserved_page ClearPageReserved(page); <--- atomic init_page_count(page); <-- _count = 1 __free_page(page); <-- free SINGLE page free_all_bootmem free_low_memory_core_early __free_memory_core(start, end) __free_pages_memory(s_pfn, e_pfn) <- creates "order" sized batches __free_pages_bootmem(pfn, order) __free_pages_boot_core(start_page, start_pfn, order) loops from 0 to (1 << order) __ClearPageReserved(p); <-- non atomic set_page_count(p, 0); <--- _count = 0 __free_pages(page, order); <--- free BATCH -- 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/ . Don't email: email@kvack.org