From patchwork Tue Mar 26 10:14:46 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Ryan Roberts X-Patchwork-Id: 13603839 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 bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 96B14C6FD1F for ; Tue, 26 Mar 2024 10:15:31 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:References:In-Reply-To: Message-Id:Date:Subject:Cc:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=wXj9ad8Y4HxlM1KZXVViu76HfCnRaeumeGMQ/Z8Kwuc=; b=KYrYXsEiHEVvFB hgYeqzBx69mEOub5rCX0cKTyGmixHveN54JeG2aE+GX8P4/IXFyL+NZy1NMM8XWLuMqVfaVKM/QRH 5TLbfIoMVR5Hn/sieYsTYKjltSzOfCzB+44uX0TTpRlFC+GVO5JMzwMk1ECXDu+GwY6TjE4Sv30R4 iZer1aE0oQXjvHGV13QaaN0aJwgkjyTWzbYfp68ThTu0i7fuJ5RNvVDUhUgCagvE7xpi2wE3Wqgro I3dR9l/1RMnnsSYEITY9RyTHJ7pfb2rD6PxsGJqQE0LPUckwRwaM70iiGQWQn1KSXs7sikbjVgdEb iePeQJMXYdCxPvHopJeg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rp3pu-0000000404u-1k2U; Tue, 26 Mar 2024 10:15:18 +0000 Received: from foss.arm.com ([217.140.110.172]) by bombadil.infradead.org with esmtp (Exim 4.97.1 #2 (Red Hat Linux)) id 1rp3pg-00000003zx3-4AV5 for linux-arm-kernel@lists.infradead.org; Tue, 26 Mar 2024 10:15:07 +0000 Received: from usa-sjc-imap-foss1.foss.arm.com (unknown [10.121.207.14]) by usa-sjc-mx-foss1.foss.arm.com (Postfix) with ESMTP id DAC12339; Tue, 26 Mar 2024 03:15:34 -0700 (PDT) Received: from e125769.cambridge.arm.com (e125769.cambridge.arm.com [10.1.196.27]) by usa-sjc-imap-foss1.foss.arm.com (Postfix) with ESMTPSA id 13F053F64C; Tue, 26 Mar 2024 03:14:59 -0700 (PDT) From: Ryan Roberts To: Catalin Marinas , Will Deacon , Mark Rutland , Ard Biesheuvel , David Hildenbrand , Donald Dutile , Eric Chanudet Cc: Ryan Roberts , linux-arm-kernel@lists.infradead.org, linux-kernel@vger.kernel.org Subject: [PATCH v1 1/3] arm64: mm: Don't remap pgtables per- cont(pte|pmd) block Date: Tue, 26 Mar 2024 10:14:46 +0000 Message-Id: <20240326101448.3453626-2-ryan.roberts@arm.com> X-Mailer: git-send-email 2.25.1 In-Reply-To: <20240326101448.3453626-1-ryan.roberts@arm.com> References: <20240326101448.3453626-1-ryan.roberts@arm.com> MIME-Version: 1.0 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20240326_031505_261898_76472CC5 X-CRM114-Status: GOOD ( 14.23 ) X-BeenThere: linux-arm-kernel@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "linux-arm-kernel" Errors-To: linux-arm-kernel-bounces+linux-arm-kernel=archiver.kernel.org@lists.infradead.org A large part of the kernel boot time is creating the kernel linear map page tables. When rodata=full, all memory is mapped by pte. And when there is lots of physical ram, there are lots of pte tables to populate. The primary cost associated with this is mapping and unmapping the pte table memory in the fixmap; at unmap time, the TLB entry must be invalidated and this is expensive. Previously, each pmd and pte table was fixmapped/fixunmapped for each cont(pte|pmd) block of mappings (16 entries with 4K granule). This means we ended up issuing 32 TLBIs per (pmd|pte) table during the population phase. Let's fix that, and fixmap/fixunmap each page once per population, for a saving of 31 TLBIs per (pmd|pte) table. This gives a significant boot speedup. Execution time of map_mem(), which creates the kernel linear map page tables, was measured on different machines with different RAM configs: | Apple M2 VM | Ampere Altra| Ampere Altra| Ampere Altra | VM, 16G | VM, 64G | VM, 256G | Metal, 512G ---------------|-------------|-------------|-------------|------------- | ms (%) | ms (%) | ms (%) | ms (%) ---------------|-------------|-------------|-------------|------------- before | 151 (0%) | 2191 (0%) | 8990 (0%) | 17443 (0%) after | 77 (-49%) | 429 (-80%) | 1753 (-80%) | 3796 (-78%) Signed-off-by: Ryan Roberts --- arch/arm64/mm/mmu.c | 32 ++++++++++++++++++-------------- 1 file changed, 18 insertions(+), 14 deletions(-) diff --git a/arch/arm64/mm/mmu.c b/arch/arm64/mm/mmu.c index 495b732d5af3..fd91b5bdb514 100644 --- a/arch/arm64/mm/mmu.c +++ b/arch/arm64/mm/mmu.c @@ -172,12 +172,9 @@ bool pgattr_change_is_safe(u64 old, u64 new) return ((old ^ new) & ~mask) == 0; } -static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end, - phys_addr_t phys, pgprot_t prot) +static pte_t *init_pte(pte_t *ptep, unsigned long addr, unsigned long end, + phys_addr_t phys, pgprot_t prot) { - pte_t *ptep; - - ptep = pte_set_fixmap_offset(pmdp, addr); do { pte_t old_pte = __ptep_get(ptep); @@ -193,7 +190,7 @@ static void init_pte(pmd_t *pmdp, unsigned long addr, unsigned long end, phys += PAGE_SIZE; } while (ptep++, addr += PAGE_SIZE, addr != end); - pte_clear_fixmap(); + return ptep; } static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr, @@ -204,6 +201,7 @@ static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr, { unsigned long next; pmd_t pmd = READ_ONCE(*pmdp); + pte_t *ptep; BUG_ON(pmd_sect(pmd)); if (pmd_none(pmd)) { @@ -219,6 +217,7 @@ static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr, } BUG_ON(pmd_bad(pmd)); + ptep = pte_set_fixmap_offset(pmdp, addr); do { pgprot_t __prot = prot; @@ -229,20 +228,20 @@ static void alloc_init_cont_pte(pmd_t *pmdp, unsigned long addr, (flags & NO_CONT_MAPPINGS) == 0) __prot = __pgprot(pgprot_val(prot) | PTE_CONT); - init_pte(pmdp, addr, next, phys, __prot); + ptep = init_pte(ptep, addr, next, phys, __prot); phys += next - addr; } while (addr = next, addr != end); + + pte_clear_fixmap(); } -static void init_pmd(pud_t *pudp, unsigned long addr, unsigned long end, - phys_addr_t phys, pgprot_t prot, - phys_addr_t (*pgtable_alloc)(int), int flags) +static pmd_t *init_pmd(pmd_t *pmdp, unsigned long addr, unsigned long end, + phys_addr_t phys, pgprot_t prot, + phys_addr_t (*pgtable_alloc)(int), int flags) { unsigned long next; - pmd_t *pmdp; - pmdp = pmd_set_fixmap_offset(pudp, addr); do { pmd_t old_pmd = READ_ONCE(*pmdp); @@ -269,7 +268,7 @@ static void init_pmd(pud_t *pudp, unsigned long addr, unsigned long end, phys += next - addr; } while (pmdp++, addr = next, addr != end); - pmd_clear_fixmap(); + return pmdp; } static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr, @@ -279,6 +278,7 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr, { unsigned long next; pud_t pud = READ_ONCE(*pudp); + pmd_t *pmdp; /* * Check for initial section mappings in the pgd/pud. @@ -297,6 +297,7 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr, } BUG_ON(pud_bad(pud)); + pmdp = pmd_set_fixmap_offset(pudp, addr); do { pgprot_t __prot = prot; @@ -307,10 +308,13 @@ static void alloc_init_cont_pmd(pud_t *pudp, unsigned long addr, (flags & NO_CONT_MAPPINGS) == 0) __prot = __pgprot(pgprot_val(prot) | PTE_CONT); - init_pmd(pudp, addr, next, phys, __prot, pgtable_alloc, flags); + pmdp = init_pmd(pmdp, addr, next, phys, __prot, pgtable_alloc, + flags); phys += next - addr; } while (addr = next, addr != end); + + pmd_clear_fixmap(); } static void alloc_init_pud(p4d_t *p4dp, unsigned long addr, unsigned long end,