From mboxrd@z Thu Jan 1 00:00:00 1970 From: Vineet Gupta Subject: New helper to free highmem pages in larger chunks Date: Sat, 3 Oct 2015 18:25:13 +0530 Message-ID: <560FD031.3030909@synopsys.com> Mime-Version: 1.0 Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Return-path: Received: from us01smtprelay-2.synopsys.com ([198.182.47.9]:46976 "EHLO smtprelay.synopsys.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752155AbbJCM5n (ORCPT ); Sat, 3 Oct 2015 08:57:43 -0400 Sender: linux-arch-owner@vger.kernel.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