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h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=Se/Q4RmWtEvD69IDqzjJLboD9y6sVttNYm+W+lHkfKo/Jo2RbzvPTvEVMT8/lrOr8 j5T2l3yTRK0wL+6AwL9j/WT8sNNikMCDZi1HfiemBy6d7oP4PbtgLpsGf7ZfjzS8gA JzHmTdMELE3v0fr5Nt+PXe9tRxXrIIwMk750/r4l8wPIMD1TkF197IaKJAIXpCdoCV C3iyj3FqMxcajVGY7iBX+Ewig5ELysaJzx5cvwPzOcT2LQ1AH7kZQRiwVXQzz31xWQ icvdArIWD5+HLjyLgmFKbtmAeYaIcdzPVUBFo+cW2Ukl2iWn2+Sx9M5c44T7L+Qqpm pTqsYkVL39e1Q== Date: Fri, 29 Sep 2023 13:02:52 +0300 From: Mike Rapoport To: Yajun Deng Cc: akpm@linux-foundation.org, mike.kravetz@oracle.com, muchun.song@linux.dev, willy@infradead.org, david@redhat.com, linux-mm@kvack.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH v4 2/2] mm: Init page count in reserve_bootmem_region when MEMINIT_EARLY Message-ID: <20230929100252.GW3303@kernel.org> References: <20230928083302.386202-1-yajun.deng@linux.dev> <20230928083302.386202-3-yajun.deng@linux.dev> <20230929083018.GU3303@kernel.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Rspamd-Server: rspam08 X-Rspamd-Queue-Id: 4953D20024 X-Stat-Signature: obcbge5qae85z8667mkd4dyegqtfa3j4 X-Rspam-User: X-HE-Tag: 1695981831-40220 X-HE-Meta: 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 061VzlCN ZEFBxX1RF8QAcdObXoDzilbtKJkOHF0/fC/ug1elJVsbNHoyEExmbqoQ/4qD9Lg04oy/dgoxRvPl3ybNhM+achMa7kVazgduadozJMLVOVWNBEEvrS+ShSKaT4r+ZRvSrLErqcA3xeYHbQXGTQWhUzuD1C+d8KmhWDt5fAEBtgUFr+zDMFnfQ29XET+rjhrOUgJMZ60rTu+UloePRRwxBaRCef3TlHOU/t/2gM5cZhGVR8kRPKgqKfNzH+qyvjoyOg9lqlvrm7rbKG0eebYNbUj8BI9g9szFdrW+yOKWes3pgWz4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: On Fri, Sep 29, 2023 at 05:50:40PM +0800, Yajun Deng wrote: > > On 2023/9/29 16:30, Mike Rapoport wrote: > > On Thu, Sep 28, 2023 at 04:33:02PM +0800, Yajun Deng wrote: > > > memmap_init_range() would init page count of all pages, but the free > > > pages count would be reset in __free_pages_core(). There are opposite > > > operations. It's unnecessary and time-consuming when it's MEMINIT_EARLY > > > context. > > > > > > Init page count in reserve_bootmem_region when in MEMINIT_EARLY context, > > > and check the page count before reset it. > > > > > > At the same time, the INIT_LIST_HEAD in reserve_bootmem_region isn't > > > need, as it already done in __init_single_page. > > > > > > The following data was tested on an x86 machine with 190GB of RAM. > > > > > > before: > > > free_low_memory_core_early() 341ms > > > > > > after: > > > free_low_memory_core_early() 285ms > > > > > > Signed-off-by: Yajun Deng > > > --- > > > v4: same with v2. > > > v3: same with v2. > > > v2: check page count instead of check context before reset it. > > > v1: https://lore.kernel.org/all/20230922070923.355656-1-yajun.deng@linux.dev/ > > > --- > > > mm/mm_init.c | 18 +++++++++++++----- > > > mm/page_alloc.c | 20 ++++++++++++-------- > > > 2 files changed, 25 insertions(+), 13 deletions(-) > > > > > > diff --git a/mm/mm_init.c b/mm/mm_init.c > > > index 9716c8a7ade9..3ab8861e1ef3 100644 > > > --- a/mm/mm_init.c > > > +++ b/mm/mm_init.c > > > @@ -718,7 +718,7 @@ static void __meminit init_reserved_page(unsigned long pfn, int nid) > > > if (zone_spans_pfn(zone, pfn)) > > > break; > > > } > > > - __init_single_page(pfn_to_page(pfn), pfn, zid, nid, INIT_PAGE_COUNT); > > > + __init_single_page(pfn_to_page(pfn), pfn, zid, nid, 0); > > > } > > > #else > > > static inline void pgdat_set_deferred_range(pg_data_t *pgdat) {} > > > @@ -756,8 +756,8 @@ void __meminit reserve_bootmem_region(phys_addr_t start, > > > init_reserved_page(start_pfn, nid); > > > - /* Avoid false-positive PageTail() */ > > > - INIT_LIST_HEAD(&page->lru); > > > + /* Init page count for reserved region */ > > Please add a comment that describes _why_ we initialize the page count here. > Okay. > > > > > + init_page_count(page); > > > /* > > > * no need for atomic set_bit because the struct > > > @@ -888,9 +888,17 @@ void __meminit memmap_init_range(unsigned long size, int nid, unsigned long zone > > > } > > > page = pfn_to_page(pfn); > > > - __init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT); > > > - if (context == MEMINIT_HOTPLUG) > > > + > > > + /* If the context is MEMINIT_EARLY, we will init page count and > > > + * mark page reserved in reserve_bootmem_region, the free region > > > + * wouldn't have page count and we will check the pages count > > > + * in __free_pages_core. > > > + */ > > > + __init_single_page(page, pfn, zone, nid, 0); > > > + if (context == MEMINIT_HOTPLUG) { > > > + init_page_count(page); > > > __SetPageReserved(page); > > Rather than calling init_page_count() and __SetPageReserved() for > > MEMINIT_HOTPLUG you can set flags to INIT_PAGE_COUNT | INIT_PAGE_RESERVED > > an call __init_single_page() after the check for MEMINIT_HOTPLUG. > > No, the following code would cost more time than the current code in > memmap_init(). > > if (context == MEMINIT_HOTPLUG) > > __init_single_page(page, pfn, zone, nid, INIT_PAGE_COUNT | INIT_PAGE_RESERVED); > else > > __init_single_page(page, pfn, zone, nid, 0); Sorry if I wasn't clear. What I meant was to have something along these lines: enum page_init_flags flags = 0; if (context == MEMINIT_HOTPLUG) flags = INIT_PAGE_COUNT | INIT_PAGE_RESERVED; __init_single_page(page, pfn, zone, nid, flags); > > But more generally, I wonder if we have to differentiate HOTPLUG here at all. > > @David, can you comment please? > > > > > + } > > > /* > > > * Usually, we want to mark the pageblock MIGRATE_MOVABLE, > > > diff --git a/mm/page_alloc.c b/mm/page_alloc.c > > > index 06be8821d833..b868caabe8dc 100644 > > > --- a/mm/page_alloc.c > > > +++ b/mm/page_alloc.c > > > @@ -1285,18 +1285,22 @@ void __free_pages_core(struct page *page, unsigned int order) > > > unsigned int loop; > > > /* > > > - * When initializing the memmap, __init_single_page() sets the refcount > > > - * of all pages to 1 ("allocated"/"not free"). We have to set the > > > - * refcount of all involved pages to 0. > > > + * When initializing the memmap, memmap_init_range sets the refcount > > > + * of all pages to 1 ("reserved" and "free") in hotplug context. We > > > + * have to set the refcount of all involved pages to 0. Otherwise, > > > + * we don't do it, as reserve_bootmem_region only set the refcount on > > > + * reserve region ("reserved") in early context. > > > */ > > Again, why hotplug and early init should be different? > I will add a comment that describes it will save boot time. But why do we need initialize struct pages differently at boot time vs memory hotplug? Is there a reason memory hotplug cannot have page count set to 0 just like for pages reserved at boot time? > > > - prefetchw(p); > > > - for (loop = 0; loop < (nr_pages - 1); loop++, p++) { > > > - prefetchw(p + 1); > > > + if (page_count(page)) { > > > + prefetchw(p); > > > + for (loop = 0; loop < (nr_pages - 1); loop++, p++) { > > > + prefetchw(p + 1); > > > + __ClearPageReserved(p); > > > + set_page_count(p, 0); > > > + } > > > __ClearPageReserved(p); > > > set_page_count(p, 0); > > > } > > > - __ClearPageReserved(p); > > > - set_page_count(p, 0); > > > atomic_long_add(nr_pages, &page_zone(page)->managed_pages); > > > -- > > > 2.25.1 > > > -- Sincerely yours, Mike.