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zram: make compression algorithm selection possible 

Add and document `comp_algorithm' device attribute.  This attribute allows
to show supported compression and currently selected compression
algorithms:

	cat /sys/block/zram0/comp_algorithm
	[lzo] lz4

and change selected compression algorithm:
	echo lzo > /sys/block/zram0/comp_algorithm

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Acked-by: Minchan Kim <minchan@kernel.org>
Cc: Jerome Marchand <jmarchan@redhat.com>
Cc: Nitin Gupta <ngupta@vflare.org>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
hifive-unleashed-5.1
Sergey Senozhatsky 2014-04-07 15:38:17 -07:00 committed by Linus Torvalds
parent fe8eb122c8
commit e46b8a030d
6 changed files with 93 additions and 11 deletions
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8
Documentation/ABI/testing/sysfs-block-zram
View File

@ -65,6 +65,14 @@ Description:
number of backend's zcomp_strm compression streams (number of
concurrent compress operations).
What: /sys/block/zram<id>/comp_algorithm
Date: February 2014
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The comp_algorithm file is read-write and lets to show
available and selected compression algorithms, change
compression algorithm selection.
What: /sys/block/zram<id>/notify_free
Date: August 2010
Contact: Nitin Gupta <ngupta@vflare.org>

24
Documentation/blockdev/zram.txt
View File

@ -42,7 +42,21 @@ will not take any effect, because single stream compression backend implemented
as a special case and does not support dynamic max_comp_streams. Only multi
stream backend supports dynamic max_comp_streams adjustment.
3) Set Disksize
3) Select compression algorithm
Using comp_algorithm device attribute one can see available and
currently selected (shown in square brackets) compression algortithms,
change selected compression algorithm (once the device is initialised
there is no way to change compression algorithm).
Examples:
#show supported compression algorithms
cat /sys/block/zram0/comp_algorithm
lzo [lz4]
#select lzo compression algorithm
echo lzo > /sys/block/zram0/comp_algorithm
4) Set Disksize
Set disk size by writing the value to sysfs node 'disksize'.
The value can be either in bytes or you can use mem suffixes.
Examples:
@ -59,14 +73,14 @@ 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.
4) Activate:
5) Activate:
mkswap /dev/zram0
swapon /dev/zram0
mkfs.ext4 /dev/zram1
mount /dev/zram1 /tmp
5) Stats:
6) Stats:
Per-device statistics are exported as various nodes under
/sys/block/zram<id>/
disksize
@ -81,11 +95,11 @@ size of the disk when not in use so a huge zram is wasteful.
compr_data_size
mem_used_total
6) Deactivate:
7) Deactivate:
swapoff /dev/zram0
umount /dev/zram1
7) Reset:
8) Reset:
Write any positive value to 'reset' sysfs node
echo 1 > /sys/block/zram0/reset
echo 1 > /sys/block/zram1/reset

32
drivers/block/zram/zcomp.c
View File

@ -39,11 +39,20 @@ struct zcomp_strm_multi {
wait_queue_head_t strm_wait;
};
static struct zcomp_backend *backends[] = {
&zcomp_lzo,
NULL
};
static struct zcomp_backend *find_backend(const char *compress)
{
if (strncmp(compress, "lzo", 3) == 0)
return &zcomp_lzo;
return NULL;
int i = 0;
while (backends[i]) {
if (sysfs_streq(compress, backends[i]->name))
break;
i++;
}
return backends[i];
}
static void zcomp_strm_free(struct zcomp *comp, struct zcomp_strm *zstrm)
@ -251,6 +260,23 @@ static int zcomp_strm_single_create(struct zcomp *comp)
return 0;
}
/* show available compressors */
ssize_t zcomp_available_show(const char *comp, char *buf)
{
ssize_t sz = 0;
int i = 0;
while (backends[i]) {
if (sysfs_streq(comp, backends[i]->name))
sz += sprintf(buf + sz, "[%s] ", backends[i]->name);
else
sz += sprintf(buf + sz, "%s ", backends[i]->name);
i++;
}
sz += sprintf(buf + sz, "\n");
return sz;
}
int zcomp_set_max_streams(struct zcomp *comp, int num_strm)
{
return comp->set_max_streams(comp, num_strm);

2
drivers/block/zram/zcomp.h
View File

@ -50,6 +50,8 @@ struct zcomp {
void (*destroy)(struct zcomp *comp);
};
ssize_t zcomp_available_show(const char *comp, char *buf);
struct zcomp *zcomp_create(const char *comp, int max_strm);
void zcomp_destroy(struct zcomp *comp);

37
drivers/block/zram/zram_drv.c
View File

@ -141,6 +141,34 @@ static ssize_t max_comp_streams_store(struct device *dev,
return len;
}
static ssize_t comp_algorithm_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
size_t sz;
struct zram *zram = dev_to_zram(dev);
down_read(&zram->init_lock);
sz = zcomp_available_show(zram->compressor, buf);
up_read(&zram->init_lock);
return sz;
}
static ssize_t comp_algorithm_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t len)
{
struct zram *zram = dev_to_zram(dev);
down_write(&zram->init_lock);
if (init_done(zram)) {
up_write(&zram->init_lock);
pr_info("Can't change algorithm for initialized device\n");
return -EBUSY;
}
strlcpy(zram->compressor, buf, sizeof(zram->compressor));
up_write(&zram->init_lock);
return len;
}
/* flag operations needs meta->tb_lock */
static int zram_test_flag(struct zram_meta *meta, u32 index,
enum zram_pageflags flag)
@ -572,10 +600,10 @@ static ssize_t disksize_store(struct device *dev,
goto out_free_meta;
}
zram->comp = zcomp_create(default_compressor, zram->max_comp_streams);
zram->comp = zcomp_create(zram->compressor, zram->max_comp_streams);
if (!zram->comp) {
pr_info("Cannot initialise %s compressing backend\n",
default_compressor);
zram->compressor);
err = -EINVAL;
goto out_free_meta;
}
@ -735,6 +763,8 @@ 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(max_comp_streams, S_IRUGO | S_IWUSR,
max_comp_streams_show, max_comp_streams_store);
static DEVICE_ATTR(comp_algorithm, S_IRUGO | S_IWUSR,
comp_algorithm_show, comp_algorithm_store);
ZRAM_ATTR_RO(num_reads);
ZRAM_ATTR_RO(num_writes);
@ -760,6 +790,7 @@ static struct attribute *zram_disk_attrs[] = {
&dev_attr_compr_data_size.attr,
&dev_attr_mem_used_total.attr,
&dev_attr_max_comp_streams.attr,
&dev_attr_comp_algorithm.attr,
NULL,
};
@ -820,7 +851,7 @@ static int create_device(struct zram *zram, int device_id)
pr_warn("Error creating sysfs group");
goto out_free_disk;
}
strlcpy(zram->compressor, default_compressor, sizeof(zram->compressor));
zram->meta = NULL;
zram->max_comp_streams = 1;
return 0;

1
drivers/block/zram/zram_drv.h
View File

@ -101,5 +101,6 @@ struct zram {
u64 disksize; /* bytes */
int max_comp_streams;
struct zram_stats stats;
char compressor[10];
};
#endif