[PATCH 2/6] compcache: block device - internal defs

[PATCH 2/6] compcache: block device - internal defs

[Nitin Gupta]

This contains header to be used internally by block device code.
It contains flags to enable/disable debugging, stats collection and also
defines default disk size (25% of total RAM).

Signed-off-by: Nitin Gupta <nitingupta910 at gmail dot com>
---
 drivers/block/compcache.h |  147 +++++++++++++++++++++++++++++++++++++++++++++
 1 files changed, 147 insertions(+), 0 deletions(-)

diff --git a/drivers/block/compcache.h b/drivers/block/compcache.h
new file mode 100644
index 0000000..b84b5d3
--- /dev/null
+++ b/drivers/block/compcache.h
@@ -0,0 +1,147 @@
+/*
+ * Compressed RAM based swap device
+ *
+ * (C) Nitin Gupta
+ *
+ * This RAM based block device acts as swap disk.
+ * Pages swapped to this device are compressed and
+ * stored in memory.
+ *
+ * Project home: http://code.google.com/p/compcache
+ */
+
+#ifndef _COMPCACHE_H_
+#define _COMPCACHE_H_
+
+#define K(x)	((x) >> 10)
+#define KB(x)	((x) << 10)
+
+#define SECTOR_SHIFT		9
+#define SECTOR_SIZE		(1 << SECTOR_SHIFT)
+#define SECTORS_PER_PAGE_SHIFT	(PAGE_SHIFT - SECTOR_SHIFT)
+#define SECTORS_PER_PAGE	(1 << SECTORS_PER_PAGE_SHIFT)
+
+/*-- Configurable parameters */
+/* Default compcache size: 25% of total RAM */
+#define DEFAULT_COMPCACHE_PERCENT	25
+#define INIT_SIZE			KB(16)
+#define GROW_SIZE			INIT_SIZE
+/*-- */
+
+/* Message prefix */
+#define C "compcache: "
+
+/* Debugging and Stats */
+#define NOP	do { } while(0)
+
+#if (1 || defined(CONFIG_DEBUG_COMPCACHE))
+#define DEBUG	1
+#define STATS	1
+#else
+#define DEBUG	0
+#define STATS	0
+#endif
+
+/* Create /proc/compcache? */
+/* If STATS is disabled, this will give minimal compcache info */
+#define CONFIG_COMPCACHE_PROC
+
+#if DEBUG
+#define CC_DEBUG(fmt,arg...) \
+	printk(KERN_DEBUG C fmt,##arg)
+#else
+#define CC_DEBUG(fmt,arg...) NOP
+#endif
+
+/*
+ * Verbose debugging:
+ * Enable basic debugging + verbose messages spread all over code
+ */
+#define DEBUG2	0
+
+#if DEBUG2
+#define DEBUG	1
+#define STATS	1
+#define CONFIG_COMPCACHE_PROC	1
+#define CC_DEBUG2((fmt,arg...) \
+	printk(KERN_DEBUG C fmt,##arg)
+#else /* DEBUG2 */
+#define CC_DEBUG2(fmt,arg...) NOP
+#endif
+
+/* Its useless to collect stats if there is no way to export it */
+#if (STATS && !defined(CONFIG_COMPCACHE_PROC))
+#error "compcache stats is enabled but not /proc/compcache."
+#endif
+
+#if STATS
+static inline void stat_inc_if_less(size_t *stat, const size_t val1,
+						const size_t val2)
+{
+	*stat += ((val1 < val2) ? 1 : 0);
+}
+
+static inline void stat_inc(size_t *stat)
+{
+	++*stat;
+}
+
+static inline void stat_dec(size_t *stat)
+{
+	BUG_ON(*stat == 0);
+	--*stat;
+}
+
+static inline void stat_set(size_t *stat, const size_t val)
+{
+	*stat = val;
+}
+
+static inline void stat_setmax(size_t *max, const size_t cur)
+{
+	*max = (cur > *max) ? cur : *max;
+}
+#else	/* STATS */
+#define stat_inc(x)			NOP
+#define stat_dec(x)			NOP
+#define stat_set(x, v)			NOP
+#define stat_setmax(x, v)		NOP
+#define stat_inc_if_less(x, v1, v2)	NOP
+#endif	/* STATS */
+
+/*-- Data structures */
+/* Indexed by page no. */
+struct table {
+	void *addr;
+	unsigned short len;
+} __attribute__ ((packed));
+
+struct compcache {
+	void *mem_pool;
+	void *compress_workmem;
+	void *compress_buffer;
+	struct table *table;
+	struct mutex lock;
+	struct gendisk *disk;
+	size_t size;            /* In sectors */
+};
+
+#if STATS
+struct compcache_stats {
+	u32 num_reads;		/* failed + successful */
+	u32 num_writes;		/* --do-- */
+	u32 failed_reads;	/* can happen when memory is tooo low */
+	u32 failed_writes;	/* should NEVER! happen */
+	u32 invalid_io;		/* non-swap I/O requests */
+	u32 good_compress;	/* no. of pages with compression
+				 * ratio <= 50%. TODO: export full
+				 * compressed page size histogram */
+	u32 pages_expand;	/* no. of incompressible pages */
+	size_t curr_pages;	/* current no. of compressed pages */
+	size_t curr_mem;	/* current total size of compressed pages */
+	size_t peak_mem;
+};
+#endif
+/*-- */
+
+#endif

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Re: [PATCH 2/6] compcache: block device - internal defs

[Will Newton]

On Mon, Mar 24, 2008 at 3:03 PM, Nitin Gupta <nitingupta910@gmail.com> wrote:

Hi Nitin,

> This contains header to be used internally by block device code.
>  It contains flags to enable/disable debugging, stats collection and also
>  defines default disk size (25% of total RAM).
>
>  Signed-off-by: Nitin Gupta <nitingupta910 at gmail dot com>
>  ---
>   drivers/block/compcache.h |  147 +++++++++++++++++++++++++++++++++++++++++++++
>   1 files changed, 147 insertions(+), 0 deletions(-)
>
>  diff --git a/drivers/block/compcache.h b/drivers/block/compcache.h
>  new file mode 100644
>  index 0000000..b84b5d3
>  --- /dev/null
>  +++ b/drivers/block/compcache.h
>  @@ -0,0 +1,147 @@
>  +/*
>  + * Compressed RAM based swap device
>  + *
>  + * (C) Nitin Gupta
>  + *
>  + * This RAM based block device acts as swap disk.
>  + * Pages swapped to this device are compressed and
>  + * stored in memory.
>  + *
>  + * Project home: http://code.google.com/p/compcache
>  + */
>  +
>  +#ifndef _COMPCACHE_H_
>  +#define _COMPCACHE_H_
>  +
>  +#define K(x)   ((x) >> 10)
>  +#define KB(x)  ((x) << 10)
>  +
>  +#define SECTOR_SHIFT           9
>  +#define SECTOR_SIZE            (1 << SECTOR_SHIFT)
>  +#define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
>  +#define SECTORS_PER_PAGE       (1 << SECTORS_PER_PAGE_SHIFT)
>  +
>  +/*-- Configurable parameters */
>  +/* Default compcache size: 25% of total RAM */
>  +#define DEFAULT_COMPCACHE_PERCENT      25
>  +#define INIT_SIZE                      KB(16)
>  +#define GROW_SIZE                      INIT_SIZE

Maybe these could be renamed to INIT_SIZE_BYTES/GROW_SIZE_BYTES to
make the units clearer?

>  +/*-- */
>  +
>  +/* Message prefix */
>  +#define C "compcache: "
>  +
>  +/* Debugging and Stats */
>  +#define NOP    do { } while(0)
>  +
>  +#if (1 || defined(CONFIG_DEBUG_COMPCACHE))
>  +#define DEBUG  1
>  +#define STATS  1
>  +#else
>  +#define DEBUG  0
>  +#define STATS  0
>  +#endif

If DEBUG is defined unconditionally what is the point of CONFIG_DEBUG_COMPCACHE?

>  +
>  +/* Create /proc/compcache? */
>  +/* If STATS is disabled, this will give minimal compcache info */
>  +#define CONFIG_COMPCACHE_PROC
>  +
>  +#if DEBUG
>  +#define CC_DEBUG(fmt,arg...) \
>  +       printk(KERN_DEBUG C fmt,##arg)
>  +#else
>  +#define CC_DEBUG(fmt,arg...) NOP
>  +#endif

Have you thought about using pr_debug() for this? It looks like it
would simplify this file at the cost of a little flexibility.

>  +
>  +/*
>  + * Verbose debugging:
>  + * Enable basic debugging + verbose messages spread all over code
>  + */
>  +#define DEBUG2 0
>  +
>  +#if DEBUG2
>  +#define DEBUG  1
>  +#define STATS  1
>  +#define CONFIG_COMPCACHE_PROC  1
>  +#define CC_DEBUG2((fmt,arg...) \
>  +       printk(KERN_DEBUG C fmt,##arg)
>  +#else /* DEBUG2 */
>  +#define CC_DEBUG2(fmt,arg...) NOP
>  +#endif
>  +
>  +/* Its useless to collect stats if there is no way to export it */
>  +#if (STATS && !defined(CONFIG_COMPCACHE_PROC))
>  +#error "compcache stats is enabled but not /proc/compcache."
>  +#endif

So it appears that if we want DEBUG we also get STATS, which requires
/proc support enabled, so it is impossible to have just DEBUG and no
STATS or /proc support?

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Re: [PATCH 2/6] compcache: block device - internal defs

[Mariusz Kozlowski]

Hi Nitin,

>  +#define K(x)   ((x) >> 10)
>  +#define KB(x)  ((x) << 10)

Hm. These look cryptic unless you remember what they do.
Could have better names?

> +#define CC_DEBUG2((fmt,arg...) \
> +       printk(KERN_DEBUG C fmt,##arg)

Unbalanced parenthesis.

Just my 0.05zl.

	Mariusz

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Re: [PATCH 2/6] compcache: block device - internal defs

[Nitin Gupta]

On Mon, Mar 24, 2008 at 9:55 PM, Mariusz Kozlowski
<m.kozlowski@tuxland.pl> wrote:
> Hi Nitin,
>
>
>  >  +#define K(x)   ((x) >> 10)
>  >  +#define KB(x)  ((x) << 10)
>
>  Hm. These look cryptic unless you remember what they do.
>  Could have better names?

I'll give them better names/add comments.

>
>
>  > +#define CC_DEBUG2((fmt,arg...) \
>  > +       printk(KERN_DEBUG C fmt,##arg)
>
>  Unbalanced parenthesis.
>

Corrected. Thanks.

- Nitin

>  Just my 0.05zl.
>
>         Mariusz
>

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Re: [PATCH 2/6] compcache: block device - internal defs

[Nitin Gupta]

On Mon, Mar 24, 2008 at 9:35 PM, Will Newton <will.newton@gmail.com> wrote:
> On Mon, Mar 24, 2008 at 3:03 PM, Nitin Gupta <nitingupta910@gmail.com> wrote:
>
>  Hi Nitin,
>
>
>
>  > This contains header to be used internally by block device code.
>  >  It contains flags to enable/disable debugging, stats collection and also
>  >  defines default disk size (25% of total RAM).
>  >
>  >  Signed-off-by: Nitin Gupta <nitingupta910 at gmail dot com>
>  >  ---
>  >   drivers/block/compcache.h |  147 +++++++++++++++++++++++++++++++++++++++++++++
>  >   1 files changed, 147 insertions(+), 0 deletions(-)
>  >
>  >  diff --git a/drivers/block/compcache.h b/drivers/block/compcache.h
>  >  new file mode 100644
>  >  index 0000000..b84b5d3
>  >  --- /dev/null
>  >  +++ b/drivers/block/compcache.h
>  >  @@ -0,0 +1,147 @@
>  >  +/*
>  >  + * Compressed RAM based swap device
>  >  + *
>  >  + * (C) Nitin Gupta
>  >  + *
>  >  + * This RAM based block device acts as swap disk.
>  >  + * Pages swapped to this device are compressed and
>  >  + * stored in memory.
>  >  + *
>  >  + * Project home: http://code.google.com/p/compcache
>  >  + */
>  >  +
>  >  +#ifndef _COMPCACHE_H_
>  >  +#define _COMPCACHE_H_
>  >  +
>  >  +#define K(x)   ((x) >> 10)
>  >  +#define KB(x)  ((x) << 10)
>  >  +
>  >  +#define SECTOR_SHIFT           9
>  >  +#define SECTOR_SIZE            (1 << SECTOR_SHIFT)
>  >  +#define SECTORS_PER_PAGE_SHIFT (PAGE_SHIFT - SECTOR_SHIFT)
>  >  +#define SECTORS_PER_PAGE       (1 << SECTORS_PER_PAGE_SHIFT)
>  >  +
>  >  +/*-- Configurable parameters */
>  >  +/* Default compcache size: 25% of total RAM */
>  >  +#define DEFAULT_COMPCACHE_PERCENT      25
>  >  +#define INIT_SIZE                      KB(16)
>  >  +#define GROW_SIZE                      INIT_SIZE
>
>  Maybe these could be renamed to INIT_SIZE_BYTES/GROW_SIZE_BYTES to
>  make the units clearer?
>


Sounds better. I will rename these.


>
>  >  +/*-- */
>  >  +
>  >  +/* Message prefix */
>  >  +#define C "compcache: "
>  >  +
>  >  +/* Debugging and Stats */
>  >  +#define NOP    do { } while(0)
>  >  +
>  >  +#if (1 || defined(CONFIG_DEBUG_COMPCACHE))
>  >  +#define DEBUG  1
>  >  +#define STATS  1
>  >  +#else
>  >  +#define DEBUG  0
>  >  +#define STATS  0
>  >  +#endif
>
>  If DEBUG is defined unconditionally what is the point of CONFIG_DEBUG_COMPCACHE?
>
>

For now I have not added DEBUG_COMPCACHE as make option (menuconfig)
so its unconditional for now. I am now adding this option and then it
will not be unconditional.

>  >  +
>  >  +/* Create /proc/compcache? */
>  >  +/* If STATS is disabled, this will give minimal compcache info */
>  >  +#define CONFIG_COMPCACHE_PROC
>  >  +
>  >  +#if DEBUG
>  >  +#define CC_DEBUG(fmt,arg...) \
>  >  +       printk(KERN_DEBUG C fmt,##arg)
>  >  +#else
>  >  +#define CC_DEBUG(fmt,arg...) NOP
>  >  +#endif
>
>  Have you thought about using pr_debug() for this? It looks like it
>  would simplify this file at the cost of a little flexibility.
>

I want to enable/disable this debugging based on DEBUG_COMPCACHE flag.
Thats why I added these macros. I will do 'printk(KERN_DEBUG' ->
pr_debug


>
>  >  +
>  >  +/*
>  >  + * Verbose debugging:
>  >  + * Enable basic debugging + verbose messages spread all over code
>  >  + */
>  >  +#define DEBUG2 0
>  >  +
>  >  +#if DEBUG2
>  >  +#define DEBUG  1
>  >  +#define STATS  1
>  >  +#define CONFIG_COMPCACHE_PROC  1
>  >  +#define CC_DEBUG2((fmt,arg...) \
>  >  +       printk(KERN_DEBUG C fmt,##arg)
>  >  +#else /* DEBUG2 */
>  >  +#define CC_DEBUG2(fmt,arg...) NOP
>  >  +#endif
>  >  +
>  >  +/* Its useless to collect stats if there is no way to export it */
>  >  +#if (STATS && !defined(CONFIG_COMPCACHE_PROC))
>  >  +#error "compcache stats is enabled but not /proc/compcache."
>  >  +#endif
>
>  So it appears that if we want DEBUG we also get STATS, which requires
>  /proc support enabled, so it is impossible to have just DEBUG and no
>  STATS or /proc support?
>

I will decouple debug and stats so each can be enabled/disabled individually.

Thanks,
Nitin

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Re: [PATCH 2/6] compcache: block device - internal defs

[Will Newton]

On Mon, Mar 24, 2008 at 5:50 PM, Nitin Gupta <nitingupta910@gmail.com> wrote:
>  >  >  +
>  >  >  +/* Create /proc/compcache? */
>  >  >  +/* If STATS is disabled, this will give minimal compcache info */
>  >  >  +#define CONFIG_COMPCACHE_PROC
>  >  >  +
>  >  >  +#if DEBUG
>  >  >  +#define CC_DEBUG(fmt,arg...) \
>  >  >  +       printk(KERN_DEBUG C fmt,##arg)
>  >  >  +#else
>  >  >  +#define CC_DEBUG(fmt,arg...) NOP
>  >  >  +#endif
>  >
>  >  Have you thought about using pr_debug() for this? It looks like it
>  >  would simplify this file at the cost of a little flexibility.
>  >
>
>  I want to enable/disable this debugging based on DEBUG_COMPCACHE flag.
>  Thats why I added these macros. I will do 'printk(KERN_DEBUG' ->
>  pr_debug

The definition of pr_debug (kernel.h) is already surrounded by #ifdef
DEBUG so it may give you the same behaviour as the CC_DEBUG macro.

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Re: [PATCH 2/6] compcache: block device - internal defs

[Nitin Gupta]

On Tuesday 25 March 2008 02:06:02 am Will Newton wrote:
> On Mon, Mar 24, 2008 at 5:50 PM, Nitin Gupta <nitingupta910@gmail.com> wrote:
> >  >  >  +
> >  >  >  +/* Create /proc/compcache? */
> >  >  >  +/* If STATS is disabled, this will give minimal compcache info */
> >  >  >  +#define CONFIG_COMPCACHE_PROC
> >  >  >  +
> >  >  >  +#if DEBUG
> >  >  >  +#define CC_DEBUG(fmt,arg...) \
> >  >  >  +       printk(KERN_DEBUG C fmt,##arg)
> >  >  >  +#else
> >  >  >  +#define CC_DEBUG(fmt,arg...) NOP
> >  >  >  +#endif
> >  >
> >  >  Have you thought about using pr_debug() for this? It looks like it
> >  >  would simplify this file at the cost of a little flexibility.
> >  >
> >
> >  I want to enable/disable this debugging based on DEBUG_COMPCACHE flag.
> >  Thats why I added these macros. I will do 'printk(KERN_DEBUG' ->
> >  pr_debug
> 
> The definition of pr_debug (kernel.h) is already surrounded by #ifdef
> DEBUG so it may give you the same behaviour as the CC_DEBUG macro.
> 

Yes, I missed this point. But still, I want to have two levels of debugging. I can probably use pr_debug() for "normal" debug and CC_DEBUG for "verbose" debugging. This looks bit inconsistent, so maybe I should stick which CC_DEBUG/CC_DEBUG2 pair instead?

- Nitin

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