On 09/01/14 19:31, Greg Kroah-Hartman wrote:

On Thu, Jan 09, 2014 at 07:19:00PM +0000, Sudeep Holla wrote:

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On 08/01/14 20:27, Greg Kroah-Hartman wrote:

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On Wed, Jan 08, 2014 at 07:26:06PM +0000, Sudeep Holla wrote:

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From: Sudeep Holla <redacted>

This patch adds initial support for providing processor cache informat=

ion

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to userspace through sysfs interface. This is based on x86 implementat=

ion

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and hence the interface is intended to be fully compatible.

A per-cpu array of cache information maintained is used mainly for
sysfs-related book keeping.

Signed-off-by: Sudeep Holla <redacted>
---
 drivers/base/Makefile     |   2 +-
 drivers/base/cacheinfo.c  | 296 +++++++++++++++++++++++++++++++++++++=

+++++++++

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 include/linux/cacheinfo.h |  43 +++++++
 3 files changed, 340 insertions(+), 1 deletion(-)
 create mode 100644 drivers/base/cacheinfo.c
 create mode 100644 include/linux/cacheinfo.h

diff --git a/drivers/base/Makefile b/drivers/base/Makefile
index 94e8a80..76f07c8 100644
--- a/drivers/base/Makefile
+++ b/drivers/base/Makefile

@@ -4,7 +4,7 @@ obj-y=09=09=09:=3D core.o bus.o dd.o syscore.o \
 =09=09=09   driver.o class.o platform.o \
 =09=09=09   cpu.o firmware.o init.o map.o devres.o \
 =09=09=09   attribute_container.o transport_class.o \
-=09=09=09   topology.o
+=09=09=09   topology.o cacheinfo.o
 obj-$(CONFIG_DEVTMPFS)=09+=3D devtmpfs.o
 obj-$(CONFIG_DMA_CMA) +=3D dma-contiguous.o
 obj-y=09=09=09+=3D power/

diff --git a/drivers/base/cacheinfo.c b/drivers/base/cacheinfo.c
new file mode 100644
index 0000000..f436c31
--- /dev/null
+++ b/drivers/base/cacheinfo.c

@@ -0,0 +1,296 @@
+/*
+ * cacheinfo support - processor cache information via sysfs
+ *
+ * Copyright (C) 2013 ARM Ltd.
+ * All Rights Reserved
+ *
+ * Author: Sudeep Holla <sudeep.holla@arm.com>
+ *
+ * This program is free software; you can redistribute it and/or modi=

fy

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+ * it under the terms of the GNU General Public License version 2 as
+ * published by the Free Software Foundation.
+ *
+ * This program is distributed "as is" WITHOUT ANY WARRANTY of any
+ * kind, whether express or implied; without even the implied warrant=

y

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+ * of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ */
+#include <linux/bitops.h>
+#include <linux/cacheinfo.h>
+#include <linux/compiler.h>
+#include <linux/cpu.h>
+#include <linux/device.h>
+#include <linux/init.h>
+#include <linux/kobject.h>
+#include <linux/of.h>
+#include <linux/sched.h>
+#include <linux/slab.h>
+#include <linux/smp.h>
+#include <linux/sysfs.h>
+
+struct cache_attr {
+=09struct attribute attr;
+=09 ssize_t(*show) (unsigned int, unsigned short, char *);
+=09 ssize_t(*store) (unsigned int, unsigned short, const char *, size=

_t);

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+};
+
+/* pointer to kobject for cpuX/cache */
+static DEFINE_PER_CPU(struct kobject *, ci_cache_kobject);
+#define per_cpu_cache_kobject(cpu)     (per_cpu(ci_cache_kobject, cpu=

))

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+
+struct index_kobject {
+=09struct kobject kobj;
+=09unsigned int cpu;
+=09unsigned short index;
+};
+
+static cpumask_t cache_dev_map;
+
+/* pointer to array of kobjects for cpuX/cache/indexY */

Please don't use "raw" kobjects for this, use the device attribute
groups, that's what they are there for.  Bonus is that your code should
get a lot simpler when you do that.

Yes I now understand device attribute group simplifies the code, but I t=

hink

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kobjects are still needed as we need to track both cpu and cache index.
By reusing only cpu device kobject, we can track cpu only.

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I don't understand, you are putting things under the cpu device object,
why do you care about a "cache" kobject?
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Yes though the cache attributes are under cpu objects, it's hierarchical
something like:
/sys/devices/system/cpu/cpu<n>/cache/index<m>/<attribute_x>
<attribute_x> is unique for each pair of (cpu<n>, index<m>
index is more like cache level, but with 2 indices if they are separate(I$,=
D$)

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One thought I have is to make cache_info structure common to all archite=

cture

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(for now its ARM specific) and introduce kobject in that similar to ia64
implementation. That even eliminates lot of weak functions defined.

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Please don't use raw kobjects if at all possible, it's not good for a
variety of reasons (no userspace events, have to roll your own code,
etc.)
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Yes I understand, will try to explore other feasible solutions.

Regards,
Sudeep