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.
Signed-off-by: Minchan Kim <minc...@kernel.org>
---
Documentation/ABI/testing/sysfs-block-zram | 9 +++++++
Documentation/blockdev/zram.txt | 20 ++++++++++++---
drivers/block/zram/zram_drv.c | 41 ++++++++++++++++++++++++++++++
drivers/block/zram/zram_drv.h | 5 ++++
4 files changed, 71 insertions(+), 4 deletions(-)
diff --git a/Documentation/ABI/testing/sysfs-block-zram
b/Documentation/ABI/testing/sysfs-block-zram
index 70ec992514d0..025331c19045 100644
--- a/Documentation/ABI/testing/sysfs-block-zram
+++ b/Documentation/ABI/testing/sysfs-block-zram
@@ -119,3 +119,12 @@ 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 <minc...@kernel.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.
+ Unit: bytes
diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
index 0595c3f56ccf..9f239ff8c444 100644
--- a/Documentation/blockdev/zram.txt
+++ b/Documentation/blockdev/zram.txt
@@ -74,14 +74,26 @@ 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.
+ 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
+
+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 +108,11 @@ 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 302dd37bcea3..adc91c7ecaef 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_size(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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