Re: [PATCH v5 15/22] powerpc/mm: Avoid useless lock with single page fragments
From: Aneesh Kumar K.V <hidden>
Date: 2018-09-26 02:44:04
Also in:
lkml
Christophe Leroy [off-list ref] writes:
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 <redacted>
quoted hunk ↗ jump to hunk
Signed-off-by: Christophe Leroy <redacted> --- 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 723cd324fa34..c43e225e124d 100644 --- a/arch/powerpc/mm/pgtable-book3s64.c +++ b/arch/powerpc/mm/pgtable-book3s64.c@@ -239,6 +239,9 @@ 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