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Fri, 22 Mar 2024 10:41:09 +0000 (UTC) Received: from dovecot-director2.suse.de ([2a07:de40:b281:106:10:150:64:167]) by imap1.dmz-prg2.suse.org with ESMTPSA id tPs/M0Vg/WWRXgAAD6G6ig (envelope-from ); Fri, 22 Mar 2024 10:41:09 +0000 Message-ID: <9932ecc4-a277-4d6b-94c9-1e65917235f6@suse.cz> Date: Fri, 22 Mar 2024 11:41:09 +0100 MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH 7/9] mm: Free up PG_slab Content-Language: en-US To: Miaohe Lin , "Matthew Wilcox (Oracle)" , Naoya Horiguchi Cc: linux-mm@kvack.org, David Hildenbrand , Muchun Song , Oscar Salvador , Andrew Morton References: <20240321142448.1645400-1-willy@infradead.org> <20240321142448.1645400-8-willy@infradead.org> From: Vlastimil Babka In-Reply-To: Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit X-Rspam-User: X-Rspamd-Server: rspam12 X-Rspamd-Queue-Id: B7393C0003 X-Stat-Signature: u5ti4whp4au4zaaxb1aq4an75xq3p6ik X-HE-Tag: 1711104071-445788 X-HE-Meta: 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 352o9MMA 1z/p5hy7UNV5CVuC+9pj0RC2L70v+xGSHYcWqhkIYpMbrnJThiOWkqzc3t27BpBfJEM3EcOCnIhBDYtbPWPstJ3Dv0Y8D+RukjFAZQd3qJ5MvF2HkwovbuSIdjw2nIKEbj9+Ij5DNWX9BijY+wKfXPAxygePxt0/Hh9wkxDfNo62aGzIjfExSZDUwbZTavQTLTH8DTTgVFWywePuEsKRhomOLVKsD/8AgLT1K/M/nojQxYzaSqZuRYat4KMw5ypCCXsVykQCYC3qh8C/IOQsXgvA42SoKvU0ceTfGpQuiPlIa+i5BXTeM+5scy6h65/apKV9peZrzCRCQWuoK7n4RT9vygr17kFxuXnwsLLxYdNXH1x0yBp3W8/bn+w== 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: List-Subscribe: List-Unsubscribe: On 3/22/24 10:20, Miaohe Lin wrote: > On 2024/3/21 22:24, Matthew Wilcox (Oracle) wrote: >> Reclaim the Slab page flag by using a spare bit in PageType. We are >> perennially short of page flags for various purposes, and now that >> the original SLAB allocator has been retired, SLUB does not use the >> mapcount/page_type field. This lets us remove a number of special cases >> for ignoring mapcount on Slab pages. >> >> Signed-off-by: Matthew Wilcox (Oracle) Acked-by: Vlastimil Babka >> --- >> include/linux/page-flags.h | 21 +++++++++++++++++---- >> include/trace/events/mmflags.h | 2 +- >> mm/memory-failure.c | 9 --------- >> mm/slab.h | 2 +- >> 4 files changed, 19 insertions(+), 15 deletions(-) >> >> diff --git a/include/linux/page-flags.h b/include/linux/page-flags.h >> index 94eb8a11a321..73e0b17c7728 100644 >> --- a/include/linux/page-flags.h >> +++ b/include/linux/page-flags.h >> @@ -109,7 +109,6 @@ enum pageflags { >> PG_active, >> PG_workingset, >> PG_error, >> - PG_slab, >> PG_owner_priv_1, /* Owner use. If pagecache, fs may use*/ >> PG_arch_1, >> PG_reserved, >> @@ -524,7 +523,6 @@ PAGEFLAG(Active, active, PF_HEAD) __CLEARPAGEFLAG(Active, active, PF_HEAD) >> TESTCLEARFLAG(Active, active, PF_HEAD) >> PAGEFLAG(Workingset, workingset, PF_HEAD) >> TESTCLEARFLAG(Workingset, workingset, PF_HEAD) >> -__PAGEFLAG(Slab, slab, PF_NO_TAIL) >> PAGEFLAG(Checked, checked, PF_NO_COMPOUND) /* Used by some filesystems */ >> >> /* Xen */ >> @@ -931,7 +929,7 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) >> #endif >> >> /* >> - * For pages that are never mapped to userspace (and aren't PageSlab), >> + * For pages that are never mapped to userspace, >> * page_type may be used. Because it is initialised to -1, we invert the >> * sense of the bit, so __SetPageFoo *clears* the bit used for PageFoo, and >> * __ClearPageFoo *sets* the bit used for PageFoo. We reserve a few high and >> @@ -947,6 +945,7 @@ PAGEFLAG_FALSE(HasHWPoisoned, has_hwpoisoned) >> #define PG_table 0x00000200 >> #define PG_guard 0x00000400 >> #define PG_hugetlb 0x00000800 >> +#define PG_slab 0x00001000 >> >> #define PageType(page, flag) \ >> ((page->page_type & (PAGE_TYPE_BASE | flag)) == PAGE_TYPE_BASE) >> @@ -1041,6 +1040,20 @@ PAGE_TYPE_OPS(Table, table, pgtable) >> */ >> PAGE_TYPE_OPS(Guard, guard, guard) >> >> +FOLIO_TYPE_OPS(slab, slab) >> + >> +/** >> + * PageSlab - Determine if the page belongs to the slab allocator >> + * @page: The page to test. >> + * >> + * Context: Any context. >> + * Return: True for slab pages, false for any other kind of page. >> + */ >> +static inline bool PageSlab(const struct page *page) >> +{ >> + return folio_test_slab(page_folio(page)); >> +} >> + >> #ifdef CONFIG_HUGETLB_PAGE >> FOLIO_TYPE_OPS(hugetlb, hugetlb) >> #else >> @@ -1121,7 +1134,7 @@ static __always_inline void __ClearPageAnonExclusive(struct page *page) >> (1UL << PG_lru | 1UL << PG_locked | \ >> 1UL << PG_private | 1UL << PG_private_2 | \ >> 1UL << PG_writeback | 1UL << PG_reserved | \ >> - 1UL << PG_slab | 1UL << PG_active | \ >> + 1UL << PG_active | \ >> 1UL << PG_unevictable | __PG_MLOCKED | LRU_GEN_MASK) >> >> /* >> diff --git a/include/trace/events/mmflags.h b/include/trace/events/mmflags.h >> index d55e53ac91bd..e46d6e82765e 100644 >> --- a/include/trace/events/mmflags.h >> +++ b/include/trace/events/mmflags.h >> @@ -107,7 +107,6 @@ >> DEF_PAGEFLAG_NAME(lru), \ >> DEF_PAGEFLAG_NAME(active), \ >> DEF_PAGEFLAG_NAME(workingset), \ >> - DEF_PAGEFLAG_NAME(slab), \ >> DEF_PAGEFLAG_NAME(owner_priv_1), \ >> DEF_PAGEFLAG_NAME(arch_1), \ >> DEF_PAGEFLAG_NAME(reserved), \ >> @@ -135,6 +134,7 @@ IF_HAVE_PG_ARCH_X(arch_3) >> #define DEF_PAGETYPE_NAME(_name) { PG_##_name, __stringify(_name) } >> >> #define __def_pagetype_names \ >> + DEF_PAGETYPE_NAME(slab), \ >> DEF_PAGETYPE_NAME(hugetlb), \ >> DEF_PAGETYPE_NAME(offline), \ >> DEF_PAGETYPE_NAME(guard), \ >> diff --git a/mm/memory-failure.c b/mm/memory-failure.c >> index 9349948f1abf..1cb41ba7870c 100644 >> --- a/mm/memory-failure.c >> +++ b/mm/memory-failure.c >> @@ -1239,7 +1239,6 @@ static int me_huge_page(struct page_state *ps, struct page *p) >> #define mlock (1UL << PG_mlocked) >> #define lru (1UL << PG_lru) >> #define head (1UL << PG_head) >> -#define slab (1UL << PG_slab) >> #define reserved (1UL << PG_reserved) >> >> static struct page_state error_states[] = { >> @@ -1249,13 +1248,6 @@ static struct page_state error_states[] = { >> * PG_buddy pages only make a small fraction of all free pages. >> */ >> >> - /* >> - * Could in theory check if slab page is free or if we can drop >> - * currently unused objects without touching them. But just >> - * treat it as standard kernel for now. >> - */ >> - { slab, slab, MF_MSG_SLAB, me_kernel }, > > Will it be better to leave the above slab case here to catch possible unhandled obscure races with > slab? Though it looks like slab page shouldn't reach here. The code would need to handle page types as it's no longer a page flag. I guess that's your decision? If it's not necessary, then I guess MF_MSG_SLAB itself could be also removed with a buch of more code referencing it. > Thanks. >