Re: [RFC 3/3] zram: limit memory size for zram

[Minchan Kim]

Another idea: we could define void zs_limit_mem(unsinged long nr_pages)
in zsmalloc and put the limit in zs_pool via new API from zram so that
zs_malloc could be failed as soon as it exceeds the limit.

In the end, zram doesn't need to call zs_get_total_size_bytes on every
write. It's more clean and right layer, IMHO.

On Tue, Aug 05, 2014 at 05:02:03PM +0900, Minchan Kim wrote:
> I have received a request several time from zram users.
> They want to limit memory size for zram because zram can consume
> lot of memory on system without limit so it makes memory management
> control hard.
> 
> This patch adds new knob to limit memory of zram.
> 
> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
>  Documentation/blockdev/zram.txt |  1 +
>  drivers/block/zram/zram_drv.c   | 41 +++++++++++++++++++++++++++++++++++++++++
>  drivers/block/zram/zram_drv.h   |  1 +
>  3 files changed, 43 insertions(+)
> 
> diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
> index d24534bee763..fcb0561dfe2e 100644
> --- a/Documentation/blockdev/zram.txt
> +++ b/Documentation/blockdev/zram.txt
> @@ -96,6 +96,7 @@ size of the disk when not in use so a huge zram is wasteful.
>  		compr_data_size
>  		mem_used_total
>  		mem_used_max
> +		mem_limit
>  
>  7) Deactivate:
>  	swapoff /dev/zram0
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index a4d637b4db7d..47f68bbb2c44 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -137,6 +137,37 @@ 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_bytes;
> +	up_read(&zram->init_lock);
> +
> +	return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
> +}
> +
> +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);
> +	int ret;
> +
> +	ret = kstrtoull(buf, 0, &limit);
> +	if (ret < 0)
> +		return ret;
> +
> +	down_write(&zram->init_lock);
> +	zram->limit_bytes = limit;
> +	ret = len;
> +	up_write(&zram->init_lock);
> +	return ret;
> +}
> +
>  static ssize_t max_comp_streams_store(struct device *dev,
>  		struct device_attribute *attr, const char *buf, size_t len)
>  {
> @@ -511,6 +542,14 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
>  		ret = -ENOMEM;
>  		goto out;
>  	}
> +
> +	if (zram->limit_bytes &&
> +		zs_get_total_size_bytes(meta->mem_pool) >= zram->limit_bytes) {
> +		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)) {
> @@ -854,6 +893,7 @@ 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_used_max, S_IRUGO, mem_used_max_show, NULL);
> +static DEVICE_ATTR(mem_limit, S_IRUGO, 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,
> @@ -883,6 +923,7 @@ static struct attribute *zram_disk_attrs[] = {
>  	&dev_attr_compr_data_size.attr,
>  	&dev_attr_mem_used_total.attr,
>  	&dev_attr_mem_used_max.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 7f21c145e317..c0d497ff6efc 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -99,6 +99,7 @@ struct zram {
>  	 * we can store in a disk.
>  	 */
>  	u64 disksize;	/* bytes */
> +	u64 limit_bytes;
>  	int max_comp_streams;
>  	struct zram_stats stats;
>  	char compressor[10];
> -- 
> 2.0.0

-- 
Kind regards,
Minchan Kim
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