Re: [RFC 2/3] zsmalloc/zram: add zs_get_max_size_bytes and use it in zram

[Seth Jennings]

On Tue, Aug 05, 2014 at 05:02:02PM +0900, Minchan Kim wrote:
> Normally, zram user can get maximum memory zsmalloc consumed via
> polling mem_used_total with sysfs in userspace.
> 
> But it has a critical problem because user can miss peak memory
> usage during update interval so that gap between them could be
> huge when memory pressure is really heavy.
> 
> This patch adds new API zs_get_max_size_bytes in zsmalloc so
> user(ex, zram) doesn't need to poll in short interval to get
> exact value.
> 
> User can just see max memory usage once his test workload is
> done. It's pretty handy and accurate.
> 
> Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> ---
>  Documentation/blockdev/zram.txt |  1 +
>  drivers/block/zram/zram_drv.c   | 17 +++++++++++++++++
>  include/linux/zsmalloc.h        |  1 +
>  mm/zsmalloc.c                   | 20 ++++++++++++++++++++
>  4 files changed, 39 insertions(+)
> 
> diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
> index 0595c3f56ccf..d24534bee763 100644
> --- a/Documentation/blockdev/zram.txt
> +++ b/Documentation/blockdev/zram.txt
> @@ -95,6 +95,7 @@ size of the disk when not in use so a huge zram is wasteful.
>  		orig_data_size
>  		compr_data_size
>  		mem_used_total
> +		mem_used_max
>  
>  7) Deactivate:
>  	swapoff /dev/zram0
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index 36e54be402df..a4d637b4db7d 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -109,6 +109,21 @@ static ssize_t mem_used_total_show(struct device *dev,
>  	return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
>  }
>  
> +static ssize_t mem_used_max_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;
> +
> +	down_read(&zram->init_lock);
> +	if (init_done(zram))
> +		val = zs_get_max_size_bytes(meta->mem_pool);
> +	up_read(&zram->init_lock);
> +
> +	return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
> +}
> +
>  static ssize_t max_comp_streams_show(struct device *dev,
>  		struct device_attribute *attr, char *buf)
>  {
> @@ -838,6 +853,7 @@ 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_used_max, S_IRUGO, mem_used_max_show, NULL);
>  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,
> @@ -866,6 +882,7 @@ 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_used_max.attr,
>  	&dev_attr_max_comp_streams.attr,
>  	&dev_attr_comp_algorithm.attr,
>  	NULL,
> diff --git a/include/linux/zsmalloc.h b/include/linux/zsmalloc.h
> index e44d634e7fb7..fb087ca06a88 100644
> --- a/include/linux/zsmalloc.h
> +++ b/include/linux/zsmalloc.h
> @@ -47,5 +47,6 @@ void *zs_map_object(struct zs_pool *pool, unsigned long handle,
>  void zs_unmap_object(struct zs_pool *pool, unsigned long handle);
>  
>  u64 zs_get_total_size_bytes(struct zs_pool *pool);
> +u64 zs_get_max_size_bytes(struct zs_pool *pool);
>  
>  #endif
> diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
> index a6089bd26621..3b5be076268a 100644
> --- a/mm/zsmalloc.c
> +++ b/mm/zsmalloc.c
> @@ -219,6 +219,7 @@ struct zs_pool {
>  
>  	gfp_t flags;	/* allocation flags used when growing pool */
>  	unsigned long pages_allocated;
> +	unsigned long max_pages_allocated;

Same here with atomic.

Seth

>  };
>  
>  /*
> @@ -946,6 +947,8 @@ unsigned long zs_malloc(struct zs_pool *pool, size_t size)
>  		set_zspage_mapping(first_page, class->index, ZS_EMPTY);
>  		spin_lock(&pool->stat_lock);
>  		pool->pages_allocated += class->pages_per_zspage;
> +		if (pool->max_pages_allocated < pool->pages_allocated)
> +			pool->max_pages_allocated = pool->pages_allocated;
>  		spin_unlock(&pool->stat_lock);
>  		spin_lock(&class->lock);
>  	}
> @@ -1101,6 +1104,9 @@ void zs_unmap_object(struct zs_pool *pool, unsigned long handle)
>  }
>  EXPORT_SYMBOL_GPL(zs_unmap_object);
>  
> +/*
> + * Reports current memory usage consumed by zs_malloc
> + */
>  u64 zs_get_total_size_bytes(struct zs_pool *pool)
>  {
>  	u64 npages;
> @@ -1112,6 +1118,20 @@ u64 zs_get_total_size_bytes(struct zs_pool *pool)
>  }
>  EXPORT_SYMBOL_GPL(zs_get_total_size_bytes);
>  
> +/*
> + * Reports maximum memory usage zs_malloc have consumed
> + */
> +u64 zs_get_max_size_bytes(struct zs_pool *pool)
> +{
> +	u64 npages;
> +
> +	spin_lock(&pool->stat_lock);
> +	npages = pool->max_pages_allocated;
> +	spin_unlock(&pool->stat_lock);
> +	return npages << PAGE_SHIFT;
> +}
> +EXPORT_SYMBOL_GPL(zs_get_max_size_bytes);
> +
>  module_init(zs_init);
>  module_exit(zs_exit);
>  
> -- 
> 2.0.0
> 
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