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Date: Fri, 22 Aug 2014 06:55:38 -0400
From: David Horner <ds2horner@...il.com>
To: Minchan Kim <minchan@...nel.org>
Cc: Andrew Morton <akpm@...ux-foundation.org>,
Linux-MM <linux-mm@...ck.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Jerome Marchand <jmarchan@...hat.com>, juno.choi@....com,
seungho1.park@....com, Luigi Semenzato <semenzato@...gle.com>,
Nitin Gupta <ngupta@...are.org>,
Seth Jennings <sjennings@...iantweb.net>,
Dan Streetman <ddstreet@...e.org>
Subject: Re: [PATCH v4 3/4] zram: zram memory size limitation
On Thu, Aug 21, 2014 at 8:42 PM, Minchan Kim <minchan@...nel.org> 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.
>
- Default is no limit so it doesn't break old behavior.
+ Initial state is no limit so it doesn't break old behavior.
I understand your previous post now.
I was saying that setting to either a null value or garbage
(which is interpreted as zero by memparse(buf, NULL);)
removes the limit.
I think this is "surprise" behaviour and rather the null case should
return -EINVAL
The test below should be "good enough" though not catching all garbage.
>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
> 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..b8c779d64968 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@...nel.org>
> +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" is default which means disable the limit.
> + and "0" means disable the limit. No limit is the initial state.
there should be no default in the API.
> + 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);
if (limit = 0 && buf != "0")
return -EINVAL
> + 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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