Re: [PATCH v5 3/4] zram: zram memory size limitation

[Sergey Senozhatsky]

On (08/25/14 09:05), Minchan Kim wrote:
> Since zram has no control feature to limit memory usage,
> it makes hard to manage system memrory.
> 
> This patch adds new knob "mem_limit" via sysfs to set up the
> a limit so that zram could fail allocation once it reaches
> the limit.
> 
> In addition, user could change the limit in runtime so that
> he could manage the memory more dynamically.
> 
> Initial state is no limit so it doesn't break old behavior.
> 
> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
>  Documentation/ABI/testing/sysfs-block-zram | 10 ++++++++
>  Documentation/blockdev/zram.txt            | 24 ++++++++++++++---
>  drivers/block/zram/zram_drv.c              | 41 ++++++++++++++++++++++++++++++
>  drivers/block/zram/zram_drv.h              |  5 ++++
>  4 files changed, 76 insertions(+), 4 deletions(-)
> 
> diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
> index 70ec992514d0..dbe643775ec1 100644
> --- a/Documentation/ABI/testing/sysfs-block-zram
> +++ b/Documentation/ABI/testing/sysfs-block-zram
> @@ -119,3 +119,13 @@ Description:
>  		efficiency can be calculated using compr_data_size and this
>  		statistic.
>  		Unit: bytes
> +
> +What:		/sys/block/zram<id>/mem_limit
> +Date:		August 2014
> +Contact:	Minchan Kim <minchan@xxxxxxxxxx>
> +Description:
> +		The mem_limit file is read/write and specifies the amount
> +		of memory to be able to consume memory to store store
> +		compressed data. The limit could be changed in run time
> +		and "0" means disable the limit. No limit is the initial state.

just a nitpick, sorry.
"the amount of memory to be able to consume memory to store store compressed data"
							^^^^^^^

"the maximum amount of memory ZRAM can use to store the compressed data"?

	-ss

> +		Unit: bytes
> diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
> index 0595c3f56ccf..82c6a41116db 100644
> --- a/Documentation/blockdev/zram.txt
> +++ b/Documentation/blockdev/zram.txt
> @@ -74,14 +74,30 @@ 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.
>  
> -5) Activate:
> +5) Set memory limit: Optional
> +	Set memory limit by writing the value to sysfs node 'mem_limit'.
> +	The value can be either in bytes or you can use mem suffixes.
> +	In addition, you could change the value in runtime.
> +	Examples:
> +	    # limit /dev/zram0 with 50MB memory
> +	    echo $((50*1024*1024)) > /sys/block/zram0/mem_limit
> +
> +	    # Using mem suffixes
> +	    echo 256K > /sys/block/zram0/mem_limit
> +	    echo 512M > /sys/block/zram0/mem_limit
> +	    echo 1G > /sys/block/zram0/mem_limit
> +
> +	    # To disable memory limit
> +	    echo 0 > /sys/block/zram0/mem_limit
> +
> +6) Activate:
>  	mkswap /dev/zram0
>  	swapon /dev/zram0
>  
>  	mkfs.ext4 /dev/zram1
>  	mount /dev/zram1 /tmp
>  
> -6) Stats:
> +7) Stats:
>  	Per-device statistics are exported as various nodes under
>  	/sys/block/zram<id>/
>  		disksize
> @@ -96,11 +112,11 @@ size of the disk when not in use so a huge zram is wasteful.
>  		compr_data_size
>  		mem_used_total
>  
> -7) Deactivate:
> +8) Deactivate:
>  	swapoff /dev/zram0
>  	umount /dev/zram1
>  
> -8) Reset:
> +9) Reset:
>  	Write any positive value to 'reset' sysfs node
>  	echo 1 > /sys/block/zram0/reset
>  	echo 1 > /sys/block/zram1/reset
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index f0b8b30a7128..370c355eb127 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -122,6 +122,33 @@ static ssize_t max_comp_streams_show(struct device *dev,
>  	return scnprintf(buf, PAGE_SIZE, "%d\n", val);
>  }
>  
> +static ssize_t mem_limit_show(struct device *dev,
> +		struct device_attribute *attr, char *buf)
> +{
> +	u64 val;
> +	struct zram *zram = dev_to_zram(dev);
> +
> +	down_read(&zram->init_lock);
> +	val = zram->limit_pages;
> +	up_read(&zram->init_lock);
> +
> +	return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
> +}
> +
> +static ssize_t mem_limit_store(struct device *dev,
> +		struct device_attribute *attr, const char *buf, size_t len)
> +{
> +	u64 limit;
> +	struct zram *zram = dev_to_zram(dev);
> +
> +	limit = memparse(buf, NULL);
> +	down_write(&zram->init_lock);
> +	zram->limit_pages = PAGE_ALIGN(limit) >> PAGE_SHIFT;
> +	up_write(&zram->init_lock);
> +
> +	return len;
> +}
> +
>  static ssize_t max_comp_streams_store(struct device *dev,
>  		struct device_attribute *attr, const char *buf, size_t len)
>  {
> @@ -513,6 +540,14 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  		ret = -ENOMEM;
>  		goto out;
>  	}
> +
> +	if (zram->limit_pages &&
> +		zs_get_total_pages(meta->mem_pool) > zram->limit_pages) {
> +		zs_free(meta->mem_pool, handle);
> +		ret = -ENOMEM;
> +		goto out;
> +	}
> +
>  	cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
>  
>  	if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
> @@ -617,6 +652,9 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
>  	struct zram_meta *meta;
>  
>  	down_write(&zram->init_lock);
> +
> +	zram->limit_pages = 0;
> +
>  	if (!init_done(zram)) {
>  		up_write(&zram->init_lock);
>  		return;
> @@ -857,6 +895,8 @@ static DEVICE_ATTR(initstate, S_IRUGO, initstate_show, NULL);
>  static DEVICE_ATTR(reset, S_IWUSR, NULL, reset_store);
>  static DEVICE_ATTR(orig_data_size, S_IRUGO, orig_data_size_show, NULL);
>  static DEVICE_ATTR(mem_used_total, S_IRUGO, mem_used_total_show, NULL);
> +static DEVICE_ATTR(mem_limit, S_IRUGO | S_IWUSR, mem_limit_show,
> +		mem_limit_store);
>  static DEVICE_ATTR(max_comp_streams, S_IRUGO | S_IWUSR,
>  		max_comp_streams_show, max_comp_streams_store);
>  static DEVICE_ATTR(comp_algorithm, S_IRUGO | S_IWUSR,
> @@ -885,6 +925,7 @@ static struct attribute *zram_disk_attrs[] = {
>  	&dev_attr_orig_data_size.attr,
>  	&dev_attr_compr_data_size.attr,
>  	&dev_attr_mem_used_total.attr,
> +	&dev_attr_mem_limit.attr,
>  	&dev_attr_max_comp_streams.attr,
>  	&dev_attr_comp_algorithm.attr,
>  	NULL,
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index e0f725c87cc6..b7aa9c21553f 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -112,6 +112,11 @@ struct zram {
>  	u64 disksize;	/* bytes */
>  	int max_comp_streams;
>  	struct zram_stats stats;
> +	/*
> +	 * the number of pages zram can consume for storing compressed data
> +	 */
> +	unsigned long limit_pages;
> +
>  	char compressor[10];
>  };
>  #endif
> -- 
> 2.0.0
> 
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