linux-kernel - [34-longterm 232/260] x86, kdump: Change copy_oldmem

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Date:	Sun,  2 Jan 2011 02:18:48 -0500
From:	Paul Gortmaker <paul.gortmaker@...driver.com>
To:	stable@...nel.org, linux-kernel@...r.kernel.org
Cc:	stable-review@...nel.org, Cliff Wickman <cpw@....com>,
	kexec@...ts.infradead.org, Ingo Molnar <mingo@...e.hu>,
	Paul Gortmaker <paul.gortmaker@...driver.com>
Subject: [34-longterm 232/260] x86, kdump: Change copy_oldmem_page() to use cached addressing

From: Cliff Wickman <cpw@....com>

commit 37a2f9f30a360fb03522d15c85c78265ccd80287 upstream.

The copy of /proc/vmcore to a user buffer proceeds much faster
if the kernel addresses memory as cached.

With this patch we have seen an increase in transfer rate from
less than 15MB/s to 80-460MB/s, depending on size of the
transfer. This makes a big difference in time needed to save a
system dump.

Signed-off-by: Cliff Wickman <cpw@....com>
Acked-by: "Eric W. Biederman" <ebiederm@...ssion.com>
Cc: kexec@...ts.infradead.org
LKML-Reference: <E1OtMLz-0001yp-Ia@...09.americas.sgi.com>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
Signed-off-by: Paul Gortmaker <paul.gortmaker@...driver.com>
---
 arch/x86/kernel/crash_dump_64.c |    2 +-
 1 files changed, 1 insertions(+), 1 deletions(-)

diff --git a/arch/x86/kernel/crash_dump_64.c b/arch/x86/kernel/crash_dump_64.c
index ce96a6b..9948288 100644
--- a/arch/x86/kernel/crash_dump_64.c
+++ b/arch/x86/kernel/crash_dump_64.c
@@ -34,7 +34,7 @@ ssize_t copy_oldmem_page(unsigned long pfn, char *buf,
 	if (!csize)
 		return 0;
 
-	vaddr = ioremap(pfn << PAGE_SHIFT, PAGE_SIZE);
+	vaddr = ioremap_cache(pfn << PAGE_SHIFT, PAGE_SIZE);
 	if (!vaddr)
 		return -ENOMEM;
 
-- 
1.7.3.3

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