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From: Christophe Leroy <christophe.leroy@c-s.fr>
To: Benjamin Herrenschmidt <benh@kernel.crashing.org>,
	Paul Mackerras <paulus@samba.org>,
	Michael Ellerman <mpe@ellerman.id.au>
Cc: linux-kernel@vger.kernel.org, linuxppc-dev@lists.ozlabs.org
Subject: [PATCH v6 03/20] powerpc/mm: Avoid useless lock with single page fragments
Date: Fri, 19 Oct 2018 06:54:58 +0000 (UTC)	[thread overview]
Message-ID: <7126e8b14b566b756d1fbfa31f09898b35fd8bba.1539931702.git.christophe.leroy@c-s.fr> (raw)
In-Reply-To: <cover.1539931702.git.christophe.leroy@c-s.fr>

There is no point in taking the page table lock as pte_frag or
pmd_frag are always NULL when we have only one fragment.

Reviewed-by: Aneesh Kumar K.V <aneesh.kumar@linux.ibm.com>
Signed-off-by: Christophe Leroy <christophe.leroy@c-s.fr>
---
 arch/powerpc/mm/pgtable-book3s64.c | 3 +++
 arch/powerpc/mm/pgtable-frag.c     | 3 +++
 2 files changed, 6 insertions(+)

diff --git a/arch/powerpc/mm/pgtable-book3s64.c b/arch/powerpc/mm/pgtable-book3s64.c
index 84ff3403239c..9f78db7c8c2a 100644
--- a/arch/powerpc/mm/pgtable-book3s64.c
+++ b/arch/powerpc/mm/pgtable-book3s64.c
@@ -243,6 +243,9 @@ static pmd_t *get_pmd_from_cache(struct mm_struct *mm)
 {
 	void *pmd_frag, *ret;
 
+	if (PMD_FRAG_NR == 1)
+		return NULL;
+
 	spin_lock(&mm->page_table_lock);
 	ret = mm->context.pmd_frag;
 	if (ret) {
diff --git a/arch/powerpc/mm/pgtable-frag.c b/arch/powerpc/mm/pgtable-frag.c
index d61e7c2a9a79..7544d0d7177d 100644
--- a/arch/powerpc/mm/pgtable-frag.c
+++ b/arch/powerpc/mm/pgtable-frag.c
@@ -34,6 +34,9 @@ static pte_t *get_pte_from_cache(struct mm_struct *mm)
 {
 	void *pte_frag, *ret;
 
+	if (PTE_FRAG_NR == 1)
+		return NULL;
+
 	spin_lock(&mm->page_table_lock);
 	ret = mm->context.pte_frag;
 	if (ret) {
-- 
2.13.3


  parent reply	other threads:[~2018-10-19  6:55 UTC|newest]

Thread overview: 25+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2018-10-19  6:54 [PATCH v6 00/20] Implement use of HW assistance on TLB table walk on 8xx Christophe Leroy
2018-10-19  6:54 ` [PATCH v6 01/20] Revert "powerpc/8xx: Use L1 entry APG to handle _PAGE_ACCESSED for CONFIG_SWAP" Christophe Leroy
2018-10-31  5:42   ` [v6, " Michael Ellerman
2018-10-19  6:54 ` [PATCH v6 02/20] powerpc/mm: Move pte_fragment_alloc() to a common location Christophe Leroy
2018-10-19  6:54 ` Christophe Leroy [this message]
2018-10-19  6:55 ` [PATCH v6 04/20] powerpc/mm: move platform specific mmu-xxx.h in platform directories Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 05/20] powerpc/mm: Move pgtable_t into platform headers Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 06/20] powerpc/code-patching: add a helper to get the address of a patch_site Christophe Leroy
2018-10-31  5:42   ` [v6, " Michael Ellerman
2018-10-19  6:55 ` [PATCH v6 07/20] powerpc/8xx: Use patch_site for memory setup patching Christophe Leroy
2018-10-31  5:42   ` [v6,07/20] " Michael Ellerman
2018-10-19  6:55 ` [PATCH v6 08/20] powerpc/8xx: Use patch_site for perf counters setup Christophe Leroy
2018-10-31  5:42   ` [v6,08/20] " Michael Ellerman
2018-10-19  6:55 ` [PATCH v6 09/20] powerpc/8xx: Move SW perf counters in first 32kb of memory Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 10/20] powerpc/8xx: Temporarily disable 16k pages and 512k hugepages Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 11/20] powerpc/mm: Use hardware assistance in TLB handlers on the 8xx Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 12/20] powerpc/mm: Enable 512k hugepage support with HW assistance " Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 13/20] powerpc/8xx: don't use r12/SPRN_SPRG_SCRATCH2 in TLB Miss handlers Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 14/20] powerpc/8xx: regroup TLB handler routines Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 15/20] powerpc/mm: don't use pte_alloc_one_kernel() before slab is available Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 16/20] powerpc/mm: inline pte_alloc_one() and pte_alloc_one_kernel() in PPC32 Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 17/20] powerpc/book3s32: Remove CONFIG_BOOKE dependent code Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 18/20] powerpc/mm: Extend pte_fragment functionality to nohash/32 Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 19/20] powerpc/8xx: Remove PTE_ATOMIC_UPDATES Christophe Leroy
2018-10-19  6:55 ` [PATCH v6 20/20] powerpc/mm: reintroduce 16K pages with HW assistance on 8xx Christophe Leroy

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