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zram: remove max_comp_streams device attr

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max_comp_streams device attribute has been defunct since May 2016 when
zram switched to per-CPU compression streams, remove it.

Link: https://lkml.kernel.org/r/20250303022425.285971-5-senozhatsky@chromium.org
Signed-off-by: Sergey Senozhatsky <senozhatsky@chromium.org>
Cc: Hillf Danton <hdanton@sina.com>
Cc: Kairui Song <ryncsn@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>
Cc: Sebastian Andrzej Siewior <bigeasy@linutronix.de>
Cc: Yosry Ahmed <yosry.ahmed@linux.dev>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
This commit is contained in:
Sergey Senozhatsky 2025-03-03 11:03:13 +09:00 committed by Andrew Morton
parent be656187b8
commit 4127e13c93
3 changed files with 10 additions and 57 deletions
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8
Documentation/ABI/testing/sysfs-block-zram
View File

@ -22,14 +22,6 @@ Description:
device. The reset operation frees all the memory associated
with this device.
What: /sys/block/zram<id>/max_comp_streams
Date: February 2014
Contact: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Description:
The max_comp_streams file is read-write and specifies the
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>

36
Documentation/admin-guide/blockdev/zram.rst
View File

@ -54,7 +54,7 @@ The list of possible return codes:
If you use 'echo', the returned value is set by the 'echo' utility,
and, in general case, something like::
echo 3 > /sys/block/zram0/max_comp_streams
echo foo > /sys/block/zram0/comp_algorithm
if [ $? -ne 0 ]; then
handle_error
fi
@ -73,21 +73,7 @@ This creates 4 devices: /dev/zram{0,1,2,3}
num_devices parameter is optional and tells zram how many devices should be
pre-created. Default: 1.
2) Set max number of compression streams
========================================
Regardless of the value passed to this attribute, ZRAM will always
allocate multiple compression streams - one per online CPU - thus
allowing several concurrent compression operations. The number of
allocated compression streams goes down when some of the CPUs
become offline. There is no single-compression-stream mode anymore,
unless you are running a UP system or have only 1 CPU online.
To find out how many streams are currently available::
cat /sys/block/zram0/max_comp_streams
3) Select compression algorithm
2) Select compression algorithm
===============================
Using comp_algorithm device attribute one can see available and
@ -107,7 +93,7 @@ Examples::
For the time being, the `comp_algorithm` content shows only compression
algorithms that are supported by zram.
4) Set compression algorithm parameters: Optional
3) Set compression algorithm parameters: Optional
=================================================
Compression algorithms may support specific parameters which can be
@ -138,7 +124,7 @@ better the compression ratio, it even can take negatives values for some
algorithms), for other algorithms `level` is acceleration level (the higher
the value the lower the compression ratio).
5) Set Disksize
4) Set Disksize
===============
Set disk size by writing the value to sysfs node 'disksize'.
@ -158,7 +144,7 @@ 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.
6) Set memory limit: Optional
5) Set memory limit: Optional
=============================
Set memory limit by writing the value to sysfs node 'mem_limit'.
@ -177,7 +163,7 @@ Examples::
# To disable memory limit
echo 0 > /sys/block/zram0/mem_limit
7) Activate
6) Activate
===========
::
@ -188,7 +174,7 @@ Examples::
mkfs.ext4 /dev/zram1
mount /dev/zram1 /tmp
8) Add/remove zram devices
7) Add/remove zram devices
==========================
zram provides a control interface, which enables dynamic (on-demand) device
@ -208,7 +194,7 @@ execute::
echo X > /sys/class/zram-control/hot_remove
9) Stats
8) Stats
========
Per-device statistics are exported as various nodes under /sys/block/zram<id>/
@ -228,8 +214,6 @@ mem_limit WO specifies the maximum amount of memory ZRAM can
writeback_limit WO specifies the maximum amount of write IO zram
can write out to backing device as 4KB unit
writeback_limit_enable RW show and set writeback_limit feature
max_comp_streams RW the number of possible concurrent compress
operations
comp_algorithm RW show and change the compression algorithm
algorithm_params WO setup compression algorithm parameters
compact WO trigger memory compaction
@ -310,7 +294,7 @@ a single line of text and contains the following stats separated by whitespace:
Unit: 4K bytes
============== =============================================================
10) Deactivate
9) Deactivate
==============
::
@ -318,7 +302,7 @@ a single line of text and contains the following stats separated by whitespace:
swapoff /dev/zram0
umount /dev/zram1
11) Reset
10) Reset
=========
Write any positive value to 'reset' sysfs node::

23
drivers/block/zram/zram_drv.c
View File

@ -1103,27 +1103,6 @@ static void zram_debugfs_register(struct zram *zram) {};
static void zram_debugfs_unregister(struct zram *zram) {};
#endif
/*
* We switched to per-cpu streams and this attr is not needed anymore.
* However, we will keep it around for some time, because:
* a) we may revert per-cpu streams in the future
* b) it's visible to user space and we need to follow our 2 years
* retirement rule; but we already have a number of 'soon to be
* altered' attrs, so max_comp_streams need to wait for the next
* layoff cycle.
*/
static ssize_t max_comp_streams_show(struct device *dev,
struct device_attribute *attr, char *buf)
{
return scnprintf(buf, PAGE_SIZE, "%d\n", num_online_cpus());
}
static ssize_t max_comp_streams_store(struct device *dev,
struct device_attribute *attr, const char *buf, size_t len)
{
return len;
}
static void comp_algorithm_set(struct zram *zram, u32 prio, const char *alg)
{
/* Do not free statically defined compression algorithms */
@ -2540,7 +2519,6 @@ static DEVICE_ATTR_WO(reset);
static DEVICE_ATTR_WO(mem_limit);
static DEVICE_ATTR_WO(mem_used_max);
static DEVICE_ATTR_WO(idle);
static DEVICE_ATTR_RW(max_comp_streams);
static DEVICE_ATTR_RW(comp_algorithm);
#ifdef CONFIG_ZRAM_WRITEBACK
static DEVICE_ATTR_RW(backing_dev);
@ -2562,7 +2540,6 @@ static struct attribute *zram_disk_attrs[] = {
&dev_attr_mem_limit.attr,
&dev_attr_mem_used_max.attr,
&dev_attr_idle.attr,
&dev_attr_max_comp_streams.attr,
&dev_attr_comp_algorithm.attr,
#ifdef CONFIG_ZRAM_WRITEBACK
&dev_attr_backing_dev.attr,