From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-2.5 required=3.0 tests=MAILING_LIST_MULTI,SPF_PASS, USER_AGENT_MUTT autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id C2749C5CFEB for ; Wed, 11 Jul 2018 12:49:51 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 8169720652 for ; Wed, 11 Jul 2018 12:49:51 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 8169720652 Authentication-Results: mail.kernel.org; dmarc=fail (p=none dis=none) header.from=kernel.org Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1732754AbeGKMyA (ORCPT ); Wed, 11 Jul 2018 08:54:00 -0400 Received: from mx2.suse.de ([195.135.220.15]:38090 "EHLO mx1.suse.de" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1726457AbeGKMyA (ORCPT ); Wed, 11 Jul 2018 08:54:00 -0400 X-Virus-Scanned: by amavisd-new at test-mx.suse.de Received: from relay2.suse.de (unknown [195.135.220.254]) by mx1.suse.de (Postfix) with ESMTP id D3EF7ADAB; Wed, 11 Jul 2018 12:49:47 +0000 (UTC) Date: Wed, 11 Jul 2018 14:49:47 +0200 From: Michal Hocko To: Mike Kravetz Cc: Cannon Matthews , Andrew Morton , Nadia Yvette Chambers , linux-mm@kvack.org, linux-kernel@vger.kernel.org, andreslc@google.com, pfeiner@google.com, dmatlack@google.com, gthelen@google.com Subject: Re: [PATCH] mm: hugetlb: don't zero 1GiB bootmem pages. Message-ID: <20180711124947.GB20172@dhcp22.suse.cz> References: <20180710184903.68239-1-cannonmatthews@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: User-Agent: Mutt/1.10.0 (2018-05-17) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Tue 10-07-18 13:46:57, Mike Kravetz wrote: > On 07/10/2018 11:49 AM, Cannon Matthews wrote: > > When using 1GiB pages during early boot, use the new > > memblock_virt_alloc_try_nid_raw() function to allocate memory without > > zeroing it. Zeroing out hundreds or thousands of GiB in a single core > > memset() call is very slow, and can make early boot last upwards of > > 20-30 minutes on multi TiB machines. > > > > To be safe, still zero the first sizeof(struct boomem_huge_page) bytes > > since this is used a temporary storage place for this info until > > gather_bootmem_prealloc() processes them later. > > > > The rest of the memory does not need to be zero'd as the hugetlb pages > > are always zero'd on page fault. > > > > Tested: Booted with ~3800 1G pages, and it booted successfully in > > roughly the same amount of time as with 0, as opposed to the 25+ > > minutes it would take before. > > > > Nice improvement! > > > Signed-off-by: Cannon Matthews > > --- > > mm/hugetlb.c | 7 ++++++- > > 1 file changed, 6 insertions(+), 1 deletion(-) > > > > diff --git a/mm/hugetlb.c b/mm/hugetlb.c > > index 3612fbb32e9d..c93a2c77e881 100644 > > --- a/mm/hugetlb.c > > +++ b/mm/hugetlb.c > > @@ -2101,7 +2101,7 @@ int __alloc_bootmem_huge_page(struct hstate *h) > > for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) { > > void *addr; > > > > - addr = memblock_virt_alloc_try_nid_nopanic( > > + addr = memblock_virt_alloc_try_nid_raw( > > huge_page_size(h), huge_page_size(h), > > 0, BOOTMEM_ALLOC_ACCESSIBLE, node); > > if (addr) { > > @@ -2109,7 +2109,12 @@ int __alloc_bootmem_huge_page(struct hstate *h) > > * Use the beginning of the huge page to store the > > * huge_bootmem_page struct (until gather_bootmem > > * puts them into the mem_map). > > + * > > + * memblock_virt_alloc_try_nid_raw returns non-zero'd > > + * memory so zero out just enough for this struct, the > > + * rest will be zero'd on page fault. > > */ > > + memset(addr, 0, sizeof(struct huge_bootmem_page)); > > This forced me to look at the usage of huge_bootmem_page. It is defined as: > struct huge_bootmem_page { > struct list_head list; > struct hstate *hstate; > #ifdef CONFIG_HIGHMEM > phys_addr_t phys; > #endif > }; > > The list and hstate fields are set immediately after allocating the memory > block here and elsewhere. However, I can't find any code that sets phys. > Although, it is potentially used in gather_bootmem_prealloc(). It appears > powerpc used this field at one time, but no longer does. > > Am I missing something? If yes, then I am missing it as well. phys is a cool name to grep for... Anyway, does it really make any sense to allow gigantic pages on HIGHMEM systems in the first place? -- Michal Hocko SUSE Labs