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Date:	Thu, 16 Jan 2014 09:56:45 +0900
From:	Minchan Kim <minchan@...nel.org>
To:	Sergey Senozhatsky <sergey.senozhatsky@...il.com>
Cc:	Andrew Morton <akpm@...ux-foundation.org>,
	Jerome Marchand <jmarchan@...hat.com>,
	Nitin Gupta <ngupta@...are.org>, linux-kernel@...r.kernel.org
Subject: Re: [PATCHv2 3/4] zram: rework reported to end-user zram statistics

Hello Sergey,

On Wed, Jan 15, 2014 at 01:16:16PM +0300, Sergey Senozhatsky wrote:
> 1) Introduce ZRAM_ATTR_RO macro to generate zram atomic64_t stats
> `show' functions and reduce code duplication.
> 
> 2) Remove `good' and `bad' compressed sub-requests stats. RW request may
> cause a number of RW sub-requests. zram used to account `good' compressed
> sub-queries (with compressed size less than 50% of original size), `bad'
> compressed sub-queries (with compressed size greater that 75% of original
> size), leaving sub-requests with compression size between 50% and 75% of
> original size not accounted and not reported. zram already accounts each
> sub-request's compression size so we can calculate real device compression
> ratio.
> 
> Acked-by: Minchan Kim <minchan@...nel.org>

I didn't give any Acked in this patch.
If I made you confused, Sorry about that.

This patch did more than thing you mentioned in desription.

1. Introduce macro to remove code duplication

   It's really good.

2. Change atomic_t with atomic64_t

   At a first look, I didn't want it because lots of custormer for zram
   are still 32bit machines so their cost would be increased a bit due to
   any locking facility like cmpxchg on some architectures.

   Having said that, I will support your cleanup patch now and then
   If we really have trouble with atomic stat operation, we could
   change it with percpu_counter so that it could solve atomic overhead and
   unnecessary memory space by introducing unsigned long instead of 64bit
   atomic_t.

   So, please add this comment for future just in case of forgetting.
   
3. Remove unreported some stat

   Looks good to me.

4. Changing name of some stat

   I couldn't understand what's the gain because I'm happy with
   orig_data_size and compr_data_size now.

5. Removed zram_init_device's warning

   Why? This patch doesn't include any justification.

6. Removed unused field of enum zram_pageflags

   Looks good to me.

Please, separate it with each patches so let's focus one by one.


> Acked-by: Jerome Marchand <jmarchan@...hat.com>
> Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@...il.com>
> ---
>  drivers/block/zram/zram_drv.c | 163 ++++++++++++------------------------------
>  drivers/block/zram/zram_drv.h |  17 ++---
>  2 files changed, 51 insertions(+), 129 deletions(-)
> 
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index b0bcb7e..6eb2155 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -42,6 +42,17 @@ static struct zram *zram_devices;
>  /* Module params (documentation at end) */
>  static unsigned int num_devices = 1;
>  
> +#define ZRAM_ATTR_RO(name)						\
> +static ssize_t zram_attr_##name##_show(struct device *d,		\
> +				struct device_attribute *attr, char *b)	\
> +{									\
> +	struct zram *zram = dev_to_zram(d);				\
> +	return sprintf(b, "%llu\n",					\
> +		(u64)atomic64_read(&zram->stats.name));			\
> +}									\
> +static struct device_attribute dev_attr_##name =			\
> +	__ATTR(name, S_IRUGO, zram_attr_##name##_show, NULL);
> +
>  static inline int init_done(struct zram *zram)
>  {
>  	return zram->meta != NULL;
> @@ -52,97 +63,36 @@ static inline struct zram *dev_to_zram(struct device *dev)
>  	return (struct zram *)dev_to_disk(dev)->private_data;
>  }
>  
> -static ssize_t disksize_show(struct device *dev,
> -		struct device_attribute *attr, char *buf)
> -{
> -	struct zram *zram = dev_to_zram(dev);
> -
> -	return sprintf(buf, "%llu\n", zram->disksize);
> -}
> -
> -static ssize_t initstate_show(struct device *dev,
> -		struct device_attribute *attr, char *buf)
> -{
> -	struct zram *zram = dev_to_zram(dev);
> -
> -	return sprintf(buf, "%u\n", init_done(zram));
> -}
> -
> -static ssize_t num_reads_show(struct device *dev,
> -		struct device_attribute *attr, char *buf)
> -{
> -	struct zram *zram = dev_to_zram(dev);
> -
> -	return sprintf(buf, "%llu\n",
> -			(u64)atomic64_read(&zram->stats.num_reads));
> -}
> -
> -static ssize_t num_writes_show(struct device *dev,
> -		struct device_attribute *attr, char *buf)
> -{
> -	struct zram *zram = dev_to_zram(dev);
> -
> -	return sprintf(buf, "%llu\n",
> -			(u64)atomic64_read(&zram->stats.num_writes));
> -}
> -
> -static ssize_t invalid_io_show(struct device *dev,
> -		struct device_attribute *attr, char *buf)
> -{
> -	struct zram *zram = dev_to_zram(dev);
> -
> -	return sprintf(buf, "%llu\n",
> -			(u64)atomic64_read(&zram->stats.invalid_io));
> -}
> -
> -static ssize_t notify_free_show(struct device *dev,
> -		struct device_attribute *attr, char *buf)
> -{
> -	struct zram *zram = dev_to_zram(dev);
> -
> -	return sprintf(buf, "%llu\n",
> -			(u64)atomic64_read(&zram->stats.notify_free));
> -}
> -
> -static ssize_t zero_pages_show(struct device *dev,
> -		struct device_attribute *attr, char *buf)
> -{
> -	struct zram *zram = dev_to_zram(dev);
> -
> -	return sprintf(buf, "%u\n", atomic_read(&zram->stats.pages_zero));
> -}
> -
> -static ssize_t orig_data_size_show(struct device *dev,
> +static ssize_t memory_used_show(struct device *dev,
>  		struct device_attribute *attr, char *buf)
>  {
> +	u64 val = 0;
>  	struct zram *zram = dev_to_zram(dev);
> +	struct zram_meta *meta = zram->meta;
>  
> -	return sprintf(buf, "%llu\n",
> -		(u64)(atomic_read(&zram->stats.pages_stored)) << PAGE_SHIFT);
> +	down_read(&zram->init_lock);
> +	if (init_done(zram))
> +		val = zs_get_total_size_bytes(meta->mem_pool);
> +	up_read(&zram->init_lock);
> +	return sprintf(buf, "%llu\n", val);
>  }
>  
> -static ssize_t compr_data_size_show(struct device *dev,
> +static ssize_t disksize_show(struct device *dev,
>  		struct device_attribute *attr, char *buf)
>  {
>  	struct zram *zram = dev_to_zram(dev);
> -
> -	return sprintf(buf, "%llu\n",
> -			(u64)atomic64_read(&zram->stats.compr_size));
> +	return sprintf(buf, "%llu\n", zram->disksize);
>  }
>  
> -static ssize_t mem_used_total_show(struct device *dev,
> +static ssize_t initstate_show(struct device *dev,
>  		struct device_attribute *attr, char *buf)
>  {
> -	u64 val = 0;
> +	u32 val = 0;
>  	struct zram *zram = dev_to_zram(dev);
> -	struct zram_meta *meta = zram->meta;
> -
>  	down_read(&zram->init_lock);
> -	if (init_done(zram))
> -		val = zs_get_total_size_bytes(meta->mem_pool);
> +	val = init_done(zram);
>  	up_read(&zram->init_lock);
> -
> -	return sprintf(buf, "%llu\n", val);
> +	return sprintf(buf, "%u\n", val);
>  }
>  
>  /* flag operations needs meta->tb_lock */
> @@ -293,7 +243,6 @@ static void zram_free_page(struct zram *zram, size_t index)
>  {
>  	struct zram_meta *meta = zram->meta;
>  	unsigned long handle = meta->table[index].handle;
> -	u16 size = meta->table[index].size;
>  
>  	if (unlikely(!handle)) {
>  		/*
> @@ -302,21 +251,15 @@ static void zram_free_page(struct zram *zram, size_t index)
>  		 */
>  		if (zram_test_flag(meta, index, ZRAM_ZERO)) {
>  			zram_clear_flag(meta, index, ZRAM_ZERO);
> -			atomic_dec(&zram->stats.pages_zero);
> +			atomic64_dec(&zram->stats.pages_zero);
>  		}
>  		return;
>  	}
>  
> -	if (unlikely(size > max_zpage_size))
> -		atomic_dec(&zram->stats.bad_compress);
> -
>  	zs_free(meta->mem_pool, handle);
>  
> -	if (size <= PAGE_SIZE / 2)
> -		atomic_dec(&zram->stats.good_compress);
> -
> -	atomic64_sub(meta->table[index].size, &zram->stats.compr_size);
> -	atomic_dec(&zram->stats.pages_stored);
> +	atomic64_sub(meta->table[index].size, &zram->stats.compressed_size);
> +	atomic64_dec(&zram->stats.pages_stored);
>  
>  	meta->table[index].handle = 0;
>  	meta->table[index].size = 0;
> @@ -459,7 +402,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  		zram_set_flag(meta, index, ZRAM_ZERO);
>  		write_unlock(&zram->meta->tb_lock);
>  
> -		atomic_inc(&zram->stats.pages_zero);
> +		atomic64_inc(&zram->stats.pages_zero);
>  		ret = 0;
>  		goto out;
>  	}
> @@ -478,7 +421,6 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  	}
>  
>  	if (unlikely(clen > max_zpage_size)) {
> -		atomic_inc(&zram->stats.bad_compress);
>  		clen = PAGE_SIZE;
>  		src = NULL;
>  		if (is_partial_io(bvec))
> @@ -516,11 +458,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  	write_unlock(&zram->meta->tb_lock);
>  
>  	/* Update stats */
> -	atomic64_add(clen, &zram->stats.compr_size);
> -	atomic_inc(&zram->stats.pages_stored);
> -	if (clen <= PAGE_SIZE / 2)
> -		atomic_inc(&zram->stats.good_compress);
> -
> +	atomic64_add(clen, &zram->stats.compressed_size);
> +	atomic64_inc(&zram->stats.pages_stored);
>  out:
>  	if (locked)
>  		mutex_unlock(&meta->buffer_lock);
> @@ -583,23 +522,8 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
>  
>  static void zram_init_device(struct zram *zram, struct zram_meta *meta)
>  {
> -	if (zram->disksize > 2 * (totalram_pages << PAGE_SHIFT)) {
> -		pr_info(
> -		"There is little point creating a zram of greater than "
> -		"twice the size of memory since we expect a 2:1 compression "
> -		"ratio. Note that zram uses about 0.1%% of the size of "
> -		"the disk when not in use so a huge zram is "
> -		"wasteful.\n"
> -		"\tMemory Size: %lu kB\n"
> -		"\tSize you selected: %llu kB\n"
> -		"Continuing anyway ...\n",
> -		(totalram_pages << PAGE_SHIFT) >> 10, zram->disksize >> 10
> -		);
> -	}
> -
>  	/* zram devices sort of resembles non-rotational disks */
>  	queue_flag_set_unlocked(QUEUE_FLAG_NONROT, zram->disk->queue);
> -
>  	zram->meta = meta;
>  	pr_debug("Initialization done!\n");
>  }
> @@ -771,14 +695,15 @@ static DEVICE_ATTR(disksize, S_IRUGO | S_IWUSR,
>  		disksize_show, disksize_store);
>  static DEVICE_ATTR(initstate, S_IRUGO, initstate_show, NULL);
>  static DEVICE_ATTR(reset, S_IWUSR, NULL, reset_store);
> -static DEVICE_ATTR(num_reads, S_IRUGO, num_reads_show, NULL);
> -static DEVICE_ATTR(num_writes, S_IRUGO, num_writes_show, NULL);
> -static DEVICE_ATTR(invalid_io, S_IRUGO, invalid_io_show, NULL);
> -static DEVICE_ATTR(notify_free, S_IRUGO, notify_free_show, NULL);
> -static DEVICE_ATTR(zero_pages, S_IRUGO, zero_pages_show, NULL);
> -static DEVICE_ATTR(orig_data_size, S_IRUGO, orig_data_size_show, NULL);
> -static DEVICE_ATTR(compr_data_size, S_IRUGO, compr_data_size_show, NULL);
> -static DEVICE_ATTR(mem_used_total, S_IRUGO, mem_used_total_show, NULL);
> +static DEVICE_ATTR(memory_used, S_IRUGO, memory_used_show, NULL);
> +
> +ZRAM_ATTR_RO(num_reads);
> +ZRAM_ATTR_RO(num_writes);
> +ZRAM_ATTR_RO(pages_stored);
> +ZRAM_ATTR_RO(invalid_io);
> +ZRAM_ATTR_RO(notify_free);
> +ZRAM_ATTR_RO(pages_zero);
> +ZRAM_ATTR_RO(compressed_size);
>  
>  static struct attribute *zram_disk_attrs[] = {
>  	&dev_attr_disksize.attr,
> @@ -786,12 +711,12 @@ static struct attribute *zram_disk_attrs[] = {
>  	&dev_attr_reset.attr,
>  	&dev_attr_num_reads.attr,
>  	&dev_attr_num_writes.attr,
> +	&dev_attr_pages_stored.attr,
>  	&dev_attr_invalid_io.attr,
>  	&dev_attr_notify_free.attr,
> -	&dev_attr_zero_pages.attr,
> -	&dev_attr_orig_data_size.attr,
> -	&dev_attr_compr_data_size.attr,
> -	&dev_attr_mem_used_total.attr,
> +	&dev_attr_pages_zero.attr,
> +	&dev_attr_compressed_size.attr,
> +	&dev_attr_memory_used.attr,
>  	NULL,
>  };
>  
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index e81e9cd..277023d 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -64,22 +64,19 @@ enum zram_pageflags {
>  struct table {
>  	unsigned long handle;
>  	u16 size;	/* object size (excluding header) */
> -	u8 count;	/* object ref count (not yet used) */
> -	u8 flags;
> +	u16 flags;
>  } __aligned(4);
>  
>  struct zram_stats {
> -	atomic64_t compr_size;	/* compressed size of pages stored */
> -	atomic64_t num_reads;	/* failed + successful */
> -	atomic64_t num_writes;	/* --do-- */
> -	atomic64_t failed_reads;	/* should NEVER! happen */
> +	atomic64_t num_writes;	/* number of writes */
> +	atomic64_t num_reads;	/* number of reads */
> +	atomic64_t pages_stored;	/* no. of pages currently stored */
> +	atomic64_t compressed_size;	/* compressed size of pages stored */
> +	atomic64_t pages_zero;		/* no. of zero filled pages */
> +	atomic64_t failed_reads;	/* no. of failed reads */
>  	atomic64_t failed_writes;	/* can happen when memory is too low */
>  	atomic64_t invalid_io;	/* non-page-aligned I/O requests */
>  	atomic64_t notify_free;	/* no. of swap slot free notifications */
> -	atomic_t pages_zero;		/* no. of zero filled pages */
> -	atomic_t pages_stored;	/* no. of pages currently stored */
> -	atomic_t good_compress;	/* % of pages with compression ratio<=50% */
> -	atomic_t bad_compress;	/* % of pages with compression ratio>=75% */
>  };
>  
>  struct zram_meta {
> -- 
> 1.8.5.3.493.gb139ac2
> 
> --
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-- 
Kind regards,
Minchan Kim
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