From: Alexander Kuleshov <kuleshovmail@gmail.com>
To: Ingo Molnar <mingo@redhat.com>,
Thomas Gleixner <tglx@linutronix.de>,
"H . Peter Anvin" <hpa@zytor.com>
Cc: Andrey Ryabinin <ryabinin.a.a@gmail.com>,
Andy Lutomirski <luto@kernel.org>,
Andy Shevchenko <andriy.shevchenko@linux.intel.com>,
Alexander Popov <alpopov@ptsecurity.com>,
linux-kernel@vger.kernel.org,
Alexander Kuleshov <kuleshovmail@gmail.com>
Subject: [PATCH v2] x86/head64: micro optimization: use memset instead of for loop
Date: Tue, 9 Feb 2016 19:11:57 +0600 [thread overview]
Message-ID: <1455023517-7620-1-git-send-email-kuleshovmail@gmail.com> (raw)
In-Reply-To: <20160209122809.GA5186@gmail.com>
This patch simplifies clearing of page table directories, by
the using of the fast memset() from the arch/x86/lib/memset_64.S.
Besides this, we 25 bytes is 25 bytes less than original.
text data bss dec hex filename
9735144 4970776 15474688 30180608 1cc8500 vmlinux.old
9735119 4970776 15474688 30180583 1cc84e7 vmlinux
Signed-off-by: Alexander Kuleshov <kuleshovmail@gmail.com>
---
Changelog:
v2: We got sizeof pud_p/pmd_p in the v1, but actually we need
to take sizeof of pud_p/pmd_p pointer, although their sizes are
the same.
arch/x86/kernel/head64.c | 14 +++-----------
1 file changed, 3 insertions(+), 11 deletions(-)
diff --git a/arch/x86/kernel/head64.c b/arch/x86/kernel/head64.c
index 2c0f340..1f4422d 100644
--- a/arch/x86/kernel/head64.c
+++ b/arch/x86/kernel/head64.c
@@ -40,13 +40,8 @@ pmdval_t early_pmd_flags = __PAGE_KERNEL_LARGE & ~(_PAGE_GLOBAL | _PAGE_NX);
/* Wipe all early page tables except for the kernel symbol map */
static void __init reset_early_page_tables(void)
{
- unsigned long i;
-
- for (i = 0; i < PTRS_PER_PGD-1; i++)
- early_level4_pgt[i].pgd = 0;
-
+ memset(early_level4_pgt, 0, sizeof(pgd_t)*(PTRS_PER_PGD-1));
next_early_pgt = 0;
-
write_cr3(__pa_nodebug(early_level4_pgt));
}
@@ -54,7 +49,6 @@ static void __init reset_early_page_tables(void)
int __init early_make_pgtable(unsigned long address)
{
unsigned long physaddr = address - __PAGE_OFFSET;
- unsigned long i;
pgdval_t pgd, *pgd_p;
pudval_t pud, *pud_p;
pmdval_t pmd, *pmd_p;
@@ -81,8 +75,7 @@ again:
}
pud_p = (pudval_t *)early_dynamic_pgts[next_early_pgt++];
- for (i = 0; i < PTRS_PER_PUD; i++)
- pud_p[i] = 0;
+ memset(pud_p, 0, sizeof(*pud_p) * PTRS_PER_PUD);
*pgd_p = (pgdval_t)pud_p - __START_KERNEL_map + phys_base + _KERNPG_TABLE;
}
pud_p += pud_index(address);
@@ -97,8 +90,7 @@ again:
}
pmd_p = (pmdval_t *)early_dynamic_pgts[next_early_pgt++];
- for (i = 0; i < PTRS_PER_PMD; i++)
- pmd_p[i] = 0;
+ memset(pmd_p, 0, sizeof(*pmd_p) * PTRS_PER_PMD);
*pud_p = (pudval_t)pmd_p - __START_KERNEL_map + phys_base + _KERNPG_TABLE;
}
pmd = (physaddr & PMD_MASK) + early_pmd_flags;
--
2.7.0.25.gfc10eb5
next prev parent reply other threads:[~2016-02-09 13:16 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2016-01-30 8:01 [PATCH] x86/head64: micro optimization: use memset instead of for loop Alexander Kuleshov
2016-01-30 8:26 ` [tip:x86/boot] x86/boot: Micro-optimize reset_early_page_tables() tip-bot for Alexander Kuleshov
2016-02-05 0:25 ` Yinghai Lu
2016-02-09 12:28 ` Ingo Molnar
2016-02-09 13:11 ` Alexander Kuleshov [this message]
2016-02-09 13:18 ` [PATCH v2] x86/head64: micro optimization: use memset instead of for loop Ingo Molnar
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