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From: Songmao Tian <tiansm@lemote.com>
To: linux-mips <linux-mips@linux-mips.org>,
	Ralf Baechle <ralf@linux-mips.org>
Subject: [RFC] Calculate exactly how many ptr is needed for pgd
Date: Tue, 31 Jul 2007 22:38:57 +0800	[thread overview]
Message-ID: <46AF4981.1090601@lemote.com> (raw)

Under 32-bit kernel with 4k page, a page is needed for a pgd,
but when page size > 4k, a page will be too much.

diff --git a/include/asm-mips/pgtable-32.h b/include/asm-mips/pgtable-32.h
index 2fbd47e..2a16240 100644
--- a/include/asm-mips/pgtable-32.h
+++ b/include/asm-mips/pgtable-32.h
@@ -67,7 +67,8 @@ extern int add_temporary_entry(unsigned long entrylo0, 
unsigned long entrylo1,
 #define PTE_ORDER    0
 #endif
 
-#define PTRS_PER_PGD    ((PAGE_SIZE << PGD_ORDER) / sizeof(pgd_t))
+/* Using a page for pgd will be a waste when page size > 4k */
+#define PTRS_PER_PGD    (1 << (32 - PGDIR_SHIFT))
 #define PTRS_PER_PTE    ((PAGE_SIZE << PTE_ORDER) / sizeof(pte_t))
 
 #define USER_PTRS_PER_PGD    (0x80000000UL/PGDIR_SIZE)

             reply	other threads:[~2007-07-31 14:39 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2007-07-31 14:38 Songmao Tian [this message]
     [not found] ` <5861a7880708012054u404c9b02s7141d1811d4a7fdf@mail.gmail.com>
2007-08-02  3:55   ` Fwd: [RFC] Calculate exactly how many ptr is needed for pgd Dajie Tan

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