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 Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id 5466CC43334 for ; Mon, 20 Jun 2022 14:20:24 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S243913AbiFTOUV (ORCPT ); Mon, 20 Jun 2022 10:20:21 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:51404 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1350608AbiFTOSW (ORCPT ); Mon, 20 Jun 2022 10:18:22 -0400 Received: from smtp-out2.suse.de (smtp-out2.suse.de [195.135.220.29]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 61F326455; Mon, 20 Jun 2022 06:33:00 -0700 (PDT) Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by smtp-out2.suse.de (Postfix) with ESMTPS id 0998F1F9DB; Mon, 20 Jun 2022 13:19:36 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_rsa; t=1655731176; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rKZZMpkhatWAwsf4c5mQXHZM6KStBRfdpbKIoOzCjNo=; b=XUGGVD06djaqIk0wf2BqotBUNOdYGy3zLVs480Zb5gxOSoCYeWs96BM8sBnoYC3Lumcxef FRMLO0iS10W7pzm035bWr8qA15R2So00DdpPC9vNtcFsKHVd3d9Klm4fSQWy80fNhNvx4a yDhr9az7W/2329yZ+bfccf6GFKyJXX8= DKIM-Signature: v=1; a=ed25519-sha256; c=relaxed/relaxed; d=suse.de; s=susede2_ed25519; t=1655731176; h=from:from:reply-to:date:date:message-id:message-id:to:to:cc:cc: mime-version:mime-version:content-type:content-type: in-reply-to:in-reply-to:references:references; bh=rKZZMpkhatWAwsf4c5mQXHZM6KStBRfdpbKIoOzCjNo=; b=UsuD+8zEjzbab09OqIpifsvUIMlX7T4enyXE00gR71/1P9juGvQ8M+rMdNqEVg3M15C8Ra J8S2OmNMI+7BcoAA== Received: from imap2.suse-dmz.suse.de (imap2.suse-dmz.suse.de [192.168.254.74]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature ECDSA (P-521) server-digest SHA512) (No client certificate requested) by imap2.suse-dmz.suse.de (Postfix) with ESMTPS id 5FB7E13638; Mon, 20 Jun 2022 13:19:35 +0000 (UTC) Received: from dovecot-director2.suse.de ([192.168.254.65]) by imap2.suse-dmz.suse.de with ESMTPSA id f8GjFOdzsGJ6OwAAMHmgww (envelope-from ); Mon, 20 Jun 2022 13:19:35 +0000 Date: Mon, 20 Jun 2022 15:19:33 +0200 From: Oscar Salvador To: Muchun Song Cc: akpm@linux-foundation.org, corbet@lwn.net, david@redhat.com, mike.kravetz@oracle.com, paulmck@kernel.org, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com Subject: Re: [PATCH v5 2/2] mm: memory_hotplug: make hugetlb_optimize_vmemmap compatible with memmap_on_memory Message-ID: References: <20220620110616.12056-1-songmuchun@bytedance.com> <20220620110616.12056-3-songmuchun@bytedance.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20220620110616.12056-3-songmuchun@bytedance.com> Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Mon, Jun 20, 2022 at 07:06:16PM +0800, Muchun Song wrote: > + /* > + * The READ_ONCE() is used to stabilize *pmdp in a register or > + * on the stack so that it will stop changing under the code. > + * The only concurrent operation where it can be changed is > + * split_vmemmap_huge_pmd() (*pmdp will be stable after this > + * operation). > + */ > + pmd = READ_ONCE(*pmdp); > + if (pmd_leaf(pmd)) > + vmemmap_page = pmd_page(pmd) + pte_index(vaddr); > + else > + vmemmap_page = pte_page(*pte_offset_kernel(pmdp, vaddr)); I was about to suggest to get rid of the else branch because on x86_64 we can only allocate PMD_SIZE chunks when using an alternative allocator, meaning that anything which is not a pmd_leaf can't be a PageVmemmapSelfHosted. But then I went to check the other platform that supports memmap_on_memory (arm64), and in there I can see that we fallback to populate basepages with altmap should we fail to allocate a PMD_SIZE chunk. > + /* > + * Due to HugeTLB alignment requirements and the vmemmap pages > + * being at the start of the hotplugged memory region in > + * memory_hotplug.memmap_on_memory case. Checking any vmemmap > + * page's vmemmap page if it is marked as VmemmapSelfHosted is > + * sufficient. > + * > + * [ hotplugged memory ] > + * [ section ][...][ section ] > + * [ vmemmap ][ usable memory ] > + * ^ | | | > + * +---+ | | > + * ^ | | > + * +-------+ | > + * ^ | > + * +-------------------------------------------+ > + */ > + if (PageVmemmapSelfHosted(vmemmap_page)) > + return 0; > + } > + > + return hugetlb_optimize_vmemmap_pages(h); > +} > + > void hugetlb_vmemmap_free(struct hstate *h, struct page *head) > { > unsigned long vmemmap_addr = (unsigned long)head; > unsigned long vmemmap_end, vmemmap_reuse, vmemmap_pages; > > - vmemmap_pages = hugetlb_optimize_vmemmap_pages(h); > + vmemmap_pages = vmemmap_optimizable_pages(h, head); > if (!vmemmap_pages) > return; > > - if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF) > - return; > - > static_branch_inc(&hugetlb_optimize_vmemmap_key); > > vmemmap_addr += RESERVE_VMEMMAP_SIZE; > @@ -199,10 +249,10 @@ static struct ctl_table hugetlb_vmemmap_sysctls[] = { > static __init int hugetlb_vmemmap_sysctls_init(void) > { > /* > - * If "memory_hotplug.memmap_on_memory" is enabled or "struct page" > - * crosses page boundaries, the vmemmap pages cannot be optimized. > + * If "struct page" crosses page boundaries, the vmemmap pages cannot > + * be optimized. > */ > - if (!mhp_memmap_on_memory() && is_power_of_2(sizeof(struct page))) > + if (is_power_of_2(sizeof(struct page))) > register_sysctl_init("vm", hugetlb_vmemmap_sysctls); > > return 0; > diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c > index 6662b86e9e64..3a59d4e97c03 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -43,30 +43,22 @@ > #include "shuffle.h" > > #ifdef CONFIG_MHP_MEMMAP_ON_MEMORY > -static int memmap_on_memory_set(const char *val, const struct kernel_param *kp) > -{ > - if (hugetlb_optimize_vmemmap_enabled()) > - return 0; > - return param_set_bool(val, kp); > -} > - > -static const struct kernel_param_ops memmap_on_memory_ops = { > - .flags = KERNEL_PARAM_OPS_FL_NOARG, > - .set = memmap_on_memory_set, > - .get = param_get_bool, > -}; > - > /* > * memory_hotplug.memmap_on_memory parameter > */ > static bool memmap_on_memory __ro_after_init; > -module_param_cb(memmap_on_memory, &memmap_on_memory_ops, &memmap_on_memory, 0444); > +module_param(memmap_on_memory, bool, 0444); > MODULE_PARM_DESC(memmap_on_memory, "Enable memmap on memory for memory hotplug"); > > -bool mhp_memmap_on_memory(void) > +static inline bool mhp_memmap_on_memory(void) > { > return memmap_on_memory; > } > +#else > +static inline bool mhp_memmap_on_memory(void) > +{ > + return false; > +} > #endif > > enum { > @@ -1035,7 +1027,7 @@ int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages, > struct zone *zone) > { > unsigned long end_pfn = pfn + nr_pages; > - int ret; > + int ret, i; > > ret = kasan_add_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages)); > if (ret) > @@ -1043,6 +1035,9 @@ int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages, > > move_pfn_range_to_zone(zone, pfn, nr_pages, NULL, MIGRATE_UNMOVABLE); > > + for (i = 0; i < nr_pages; i++) > + SetPageVmemmapSelfHosted(pfn_to_page(pfn + i)); > + > /* > * It might be that the vmemmap_pages fully span sections. If that is > * the case, mark those sections online here as otherwise they will be > -- > 2.11.0 > > -- Oscar Salvador SUSE Labs