linux-kernel - [PATCH] [24/31] CPA: Only unmap kernel init pages in text mapping when CONFIG_DEBUG

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Message-Id: <20080114221657.443DD14F83@wotan.suse.de>
Date:	Mon, 14 Jan 2008 23:16:57 +0100 (CET)
From:	Andi Kleen <ak@...e.de>
To:	linux-kernel@...r.kernel.org, jbeulich@...ell.com, mingo@...e.hu,
	tglx@...utronix.de
Subject: [PATCH] [24/31] CPA: Only unmap kernel init pages in text mapping when CONFIG_DEBUG_RODATA is set


Otherwise the kernel will likely always run with 4K pages instead of 2MB pages,
which is costly in terms of TLBs.

Also optimize it a little bit by using only a single change_page_attr() calls.
This is particularly useful if debugging is enabled inside it because it spams
the logs much less.

Signed-off-by: Andi Kleen <ak@...e.de>

---
 arch/x86/mm/init_64.c |    9 ++++++---
 1 file changed, 6 insertions(+), 3 deletions(-)

Index: linux/arch/x86/mm/init_64.c
===================================================================
--- linux.orig/arch/x86/mm/init_64.c
+++ linux/arch/x86/mm/init_64.c
@@ -553,13 +553,16 @@ void free_init_pages(char *what, unsigne
 		init_page_count(virt_to_page(addr));
 		memset((void *)(addr & ~(PAGE_SIZE-1)),
 			POISON_FREE_INITMEM, PAGE_SIZE);
-		if (addr >= __START_KERNEL_map)
-			change_page_attr_addr(addr, 1, __pgprot(0));
 		free_page(addr);
 		totalram_pages++;
 	}
-	if (addr > __START_KERNEL_map)
+#ifdef CONFIG_DEBUG_RODATA
+	if (begin >= __START_KERNEL_map) {
+		change_page_attr_addr(begin, (end - begin)/PAGE_SIZE,
+					__pgprot(0));
 		global_flush_tlb();
+	}
+#endif
 }
 
 void free_initmem(void)
--
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