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 E34CECCA479 for ; Fri, 17 Jun 2022 07:28:40 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1380593AbiFQH2i (ORCPT ); Fri, 17 Jun 2022 03:28:38 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:41070 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1380636AbiFQH2b (ORCPT ); Fri, 17 Jun 2022 03:28:31 -0400 Received: from mail-pg1-x536.google.com (mail-pg1-x536.google.com [IPv6:2607:f8b0:4864:20::536]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id C719E42ED7 for ; Fri, 17 Jun 2022 00:28:16 -0700 (PDT) Received: by mail-pg1-x536.google.com with SMTP id r5so3377668pgr.3 for ; Fri, 17 Jun 2022 00:28:16 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=bytedance-com.20210112.gappssmtp.com; s=20210112; h=date:from:to:cc:subject:message-id:references:mime-version :content-disposition:in-reply-to; bh=b+rfEXZ4GLjjuoJrw+X3apDxL7fB3SJwlxuDhP2gRLw=; b=leZzHlDaC8chjBI7eid/Y9ny7U2cJ+x+zmGOgrvGGE1xkxPQkQTRxjqbgsVMU8d61S MJURzbBcc6/juGlbN4N35Yz7V4IVU3RwsYfHHbaSPNuMyF5n9cGP8pel686dKGoM+wXb ys2D6FHgNTZht3H6j/QNYqVT6BGCYsS7NN75/SV9tAvqbwxa/0M9zyAeo6DcAD7CrohQ tA/3kMuObtUuAiWO0fgRHs+Yd3ctpmZtMVfA5UPwMV0bn4ENYe0PEPEQQa67p3MkbGXI LlEdU9OxqmO92e4s5x0A3zmS9OLwPBmB3mNuFLxuc4WkggOpzJHGS1vEGrrAeaWVlV6D E96Q== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:date:from:to:cc:subject:message-id:references :mime-version:content-disposition:in-reply-to; bh=b+rfEXZ4GLjjuoJrw+X3apDxL7fB3SJwlxuDhP2gRLw=; b=mrJOhItC3j0qXgYm8Q0aowmYNB0M8YtpB9dMrgcBNM0D5AY5IdQsfBtBngZHqSMWZl CVipOIX2x2EBY9+2Pi+zL0WHtZpYri3dURl9DSDWE63iwbDT0VVQVz9bwITW0Kp+guks DH/Dsx0FGRGn6Hhv/E+eMxMmNRo4vNXY0IUMhh+y1kUI24Qet8voKnXSEEPbX//eqLlU fs9jqAeZ0/Tf4hIdv782eHkWs8mj/NtZECxYjVJoMlFBBcFW10xNg65WAxpeyEwJ6aSs b969E0So/eWKhNx0IT6dRi294x+kQih9E1/oAVG7XdIloZU1ejuUsmH1v7vl6AaaHySb C2hQ== X-Gm-Message-State: AJIora/3uCXz8goTBLxL+G5Z5Ro73L+Xm3qVNVKvTDV1Zd4sQlSZCJiv SmTflfKO/WUEMp/ER7djY305xg== X-Google-Smtp-Source: AGRyM1vPPlph1s3ty+1w5MCA25O8Zvoml/8ArR/MhH1gDvCSAS1ZGO+v2FWHyehTw4AAB+zn8ryF4Q== X-Received: by 2002:a63:8648:0:b0:3fd:980d:8de4 with SMTP id x69-20020a638648000000b003fd980d8de4mr7767738pgd.198.1655450896206; Fri, 17 Jun 2022 00:28:16 -0700 (PDT) Received: from localhost ([139.177.225.255]) by smtp.gmail.com with ESMTPSA id p15-20020a170903248f00b00163c6ac211fsm584071plw.111.2022.06.17.00.28.13 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Fri, 17 Jun 2022 00:28:14 -0700 (PDT) Date: Fri, 17 Jun 2022 15:28:10 +0800 From: Muchun Song To: Oscar Salvador Cc: David Hildenbrand , corbet@lwn.net, akpm@linux-foundation.org, paulmck@kernel.org, mike.kravetz@oracle.com, linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-mm@kvack.org, duanxiongchun@bytedance.com, smuchun@gmail.com Subject: Re: [PATCH v2 2/2] mm: memory_hotplug: introduce SECTION_CANNOT_OPTIMIZE_VMEMMAP Message-ID: References: <20220520025538.21144-1-songmuchun@bytedance.com> <20220520025538.21144-3-songmuchun@bytedance.com> <53024884-0182-df5f-9ca2-00652c64ce36@redhat.com> <24d5ec20-9c9e-93aa-11f4-c4619f51f7d1@redhat.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Precedence: bulk List-ID: X-Mailing-List: linux-doc@vger.kernel.org On Fri, Jun 17, 2022 at 07:46:53AM +0200, Oscar Salvador wrote: > On Thu, Jun 16, 2022 at 09:30:33AM +0200, David Hildenbrand wrote: > > IIRC, that was used to skip these patches on the offlining path before > > we provided the ranges to offline_pages(). > > Yeah, it was designed for that purpose back then. > > > I'd not mess with PG_reserved, and give them a clearer name, to not > > confuse them with other, ordinary, vmemmap pages that are not > > self-hosted (maybe in the future we might want to flag all vmemmap pages > > with a new type?). > > Not sure whether a new type is really needed, or to put it another way, I > cannot see the benefit. > > > > > I'd just try reusing the flag PG_owner_priv_1. And eventually, flag all > > (v)memmap pages with a type PG_memmap. However, the latter would be > > optional and might not be strictly required > > > > > > So what think could make sense is > > > > /* vmemmap pages that are self-hosted and cannot be optimized/freed. */ > > PG_vmemmap_self_hosted = PG_owner_priv_1, > > Sure, I just lightly tested the below, and seems to work, but not sure > whether that is what you are referring to. > @Munchun: thoughts? > I think it works and fits my requirement. > diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h > index e66f7aa3191d..a4556afd7bda 100644 > --- a/include/linux/page-flags.h > +++ b/include/linux/page-flags.h > @@ -193,6 +193,11 @@ enum pageflags { > > /* Only valid for buddy pages. Used to track pages that are reported */ > PG_reported = PG_uptodate, > + > +#ifdef CONFIG_MEMORY_HOTPLUG > + /* For self-hosted memmap pages */ > + PG_vmemmap_self_hosted = PG_owner_priv_1, > +#endif > }; > > #define PAGEFLAGS_MASK ((1UL << NR_PAGEFLAGS) - 1) > @@ -628,6 +633,10 @@ PAGEFLAG_FALSE(SkipKASanPoison, skip_kasan_poison) > */ > __PAGEFLAG(Reported, reported, PF_NO_COMPOUND) > > +#ifdef CONFIG_MEMORY_HOTPLUG > +PAGEFLAG(Vmemmap_self_hosted, vmemmap_self_hosted, PF_ANY) > +#endif > + > /* > * On an anonymous page mapped into a user virtual memory area, > * page->mapping points to its anon_vma, not to a struct address_space; > diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c > index 1089ea8a9c98..e2de7ed27e9e 100644 > --- a/mm/hugetlb_vmemmap.c > +++ b/mm/hugetlb_vmemmap.c > @@ -101,6 +101,14 @@ 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; > + struct mem_section *ms = __pfn_to_section(page_to_pfn(head)); > + struct page *memmap; > + > + memmap = sparse_decode_mem_map(ms->section_mem_map, > + pfn_to_section_nr(page_to_pfn(head))); > + > + if (PageVmemmap_self_hosted(memmap)) > + return; I think here needs a loop if it is a 1GB page (spans multiple sections). Right? Here is an implementation based on another approach. But I think your implementation is more simpler and efficient. Would you mind me squash your diff into my patch and with your "Co-developed-by"? diff --git a/mm/hugetlb_vmemmap.c b/mm/hugetlb_vmemmap.c index fcd9f7872064..46d637acc15e 100644 --- a/mm/hugetlb_vmemmap.c +++ b/mm/hugetlb_vmemmap.c @@ -10,7 +10,7 @@ */ #define pr_fmt(fmt) "HugeTLB: " fmt -#include +#include #include "hugetlb_vmemmap.h" /* @@ -97,18 +97,79 @@ int hugetlb_vmemmap_alloc(struct hstate *h, struct page *head) return ret; } +/* + * The vmemmap of the first page of hotplugged memory falls onto itself when + * memory_hotplug.memmap_on_memory is enabled, and the vmemmap pages cannot be + * optimized in this case. We can simply lookup the first page and test if + * the vmemmap maps to itself to detect if memory_hotplug.memmap_on_memory is + * enabled for this memory block. + * + * [ hotplugged memory ] + * [ vmemmap ][ usable memory ] + * ^ | | | + * +---+ | | + * ^ | | + * +--------+ | + * ^ | + * +-----------------+ + */ +static bool memory_block_vmemmap_optimizable(unsigned long start_pfn) +{ + pmd_t *pmdp, pmd; + unsigned long pfn, vaddr; + + vaddr = (unsigned long)pfn_to_page(start_pfn); + pmdp = pmd_off_k(vaddr); + /* + * The READ_ONCE() is used to stabilize *pmdp in a register or on + * the stack so that it will stop changing under the code. + */ + pmd = READ_ONCE(*pmdp); + + if (pmd_large(pmd)) + pfn = pmd_pfn(pmd); + else + pfn = pte_pfn(*pte_offset_kernel(pmdp, vaddr)); + + return pfn != start_pfn; +} + +static unsigned int optimizable_vmemmap_pages(struct hstate *h, + struct page *head) +{ + unsigned long size = memory_block_size_bytes(); + unsigned long pfn = page_to_pfn(head); + unsigned long start = ALIGN_DOWN(pfn, size); + unsigned long end = start + pages_per_huge_page(h); + + if (READ_ONCE(vmemmap_optimize_mode) == VMEMMAP_OPTIMIZE_OFF) + return 0; + + for (; start < end; start += size) { + /* + * Fast path. The early section is always optimizable since the + * early section's vmemmap pages do not allocated from the added + * memory block itself. + */ + if (early_section(__pfn_to_section(start + (pfn & PAGE_SECTION_MASK)))) + continue; + + if (!memory_block_vmemmap_optimizable(start)) + 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 = optimizable_vmemmap_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 +260,10 @@ 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; > > vmemmap_pages = hugetlb_optimize_vmemmap_pages(h); > if (!vmemmap_pages) > @@ -199,10 +207,10 @@ 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 1213d0c67a53..863966c2c6f1 100644 > --- a/mm/memory_hotplug.c > +++ b/mm/memory_hotplug.c > @@ -45,8 +45,6 @@ > #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); > } > > @@ -1032,6 +1030,7 @@ int mhp_init_memmap_on_memory(unsigned long pfn, unsigned long nr_pages, > { > unsigned long end_pfn = pfn + nr_pages; > int ret; > + int i; > > ret = kasan_add_zero_shadow(__va(PFN_PHYS(pfn)), PFN_PHYS(nr_pages)); > if (ret) > @@ -1039,6 +1038,12 @@ 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); > > + /* > + * Let us flag self-hosted memmap > + */ > + for (i = 0; i < nr_pages; i++) > + SetPageVmemmap_self_hosted(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 > > > -- > Oscar Salvador > SUSE Labs >