[PATCH] x86: Expose loops_per_jiffy through /proc/cpuinfo.

[PATCH] x86: Expose loops_per_jiffy through /proc/cpuinfo.

[Richard W.M. Jones]

From: "Richard W.M. Jones" <rjones@redhat.com>

When we run the current kernel using qemu with TCG (software emulation
of x86), adding the lpj= option to the guest kernel helps greatly with
clock stability especially when the host is heavily loaded.

Currently the calculated 'lpj=...' argument is printed by the kernel
during boot, but isn't available after boot (eg. if boot messages have
scrolled off the kernel message ring).  It is also not possible to
calculate lpj from available information, especially as non-root.

This adds lpj to /proc/cpuinfo information so it is always available.

Signed-off-by: Richard W.M. Jones <rjones@redhat.com>
---
 arch/x86/kernel/cpu/proc.c | 1 +
 1 file changed, 1 insertion(+)

diff --git a/arch/x86/kernel/cpu/proc.c b/arch/x86/kernel/cpu/proc.c
index e280253..bf9c2e8 100644
--- a/arch/x86/kernel/cpu/proc.c
+++ b/arch/x86/kernel/cpu/proc.c
@@ -103,6 +103,7 @@ static int show_cpuinfo(struct seq_file *m, void *v)
 	seq_printf(m, "\nbogomips\t: %lu.%02lu\n",
 		   c->loops_per_jiffy/(500000/HZ),
 		   (c->loops_per_jiffy/(5000/HZ)) % 100);
+	seq_printf(m, "lpj\t\t: %lu\n", c->loops_per_jiffy);
 
 #ifdef CONFIG_X86_64
 	if (c->x86_tlbsize > 0)
-- 
1.8.1.2

Re: [PATCH] x86: Expose loops_per_jiffy through /proc/cpuinfo.

[Richard W.M. Jones]

Ignore this patch, it's obviously wrong.  Too late in the afternoon ...

Rich.

-- 
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Re: [PATCH] x86: Expose loops_per_jiffy through /proc/cpuinfo.

[Richard W.M. Jones]

On Fri, Mar 01, 2013 at 04:46:43PM +0000, Richard W.M. Jones wrote:
> Ignore this patch, it's obviously wrong.  Too late in the afternoon ...

Actually, NOT wrong.  You can't get HZ from userspace, so
exporting loops_per_jiffy like this is necessary.

Rich.

-- 
Richard Jones, Virtualization Group, Red Hat http://people.redhat.com/~rjones
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