The patch titled
Subject: zram: remove max_comp_streams device attr
has been added to the -mm mm-unstable branch. Its filename is
zram-remove-max_comp_streams-device-attr.patch
This patch will shortly appear at
https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/zram-remove-max_comp_streams-device-attr.patch
This patch will later appear in the mm-unstable branch at
git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm
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------------------------------------------------------
From: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Subject: zram: remove max_comp_streams device attr
Date: Sat, 22 Feb 2025 07:25:35 +0900
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/20250221222958.2225035-5-senozhatsky@xxxxxxxxxxxx
Signed-off-by: Sergey Senozhatsky <senozhatsky@xxxxxxxxxxxx>
Cc: Hillf Danton <hdanton@xxxxxxxx>
Cc: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Sebastian Andrzej Siewior <bigeasy@xxxxxxxxxxxxx>
Cc: Yosry Ahmed <yosry.ahmed@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-block-zram | 8 ----
Documentation/admin-guide/blockdev/zram.rst | 36 +++++-------------
drivers/block/zram/zram_drv.c | 23 -----------
3 files changed, 10 insertions(+), 57 deletions(-)
--- a/Documentation/ABI/testing/sysfs-block-zram~zram-remove-max_comp_streams-device-attr
+++ a/Documentation/ABI/testing/sysfs-block-zram
@@ -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@xxxxxxxxx>
-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@xxxxxxxxx>
--- a/Documentation/admin-guide/blockdev/zram.rst~zram-remove-max_comp_streams-device-attr
+++ a/Documentation/admin-guide/blockdev/zram.rst
@@ -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,
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 ca
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
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 maxi
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 f
Unit: 4K bytes
============== =============================================================
-10) Deactivate
+9) Deactivate
==============
::
@@ -318,7 +302,7 @@ a single line of text and contains the f
swapoff /dev/zram0
umount /dev/zram1
-11) Reset
+10) Reset
=========
Write any positive value to 'reset' sysfs node::
--- a/drivers/block/zram/zram_drv.c~zram-remove-max_comp_streams-device-attr
+++ a/drivers/block/zram/zram_drv.c
@@ -1109,27 +1109,6 @@ static void zram_debugfs_register(struct
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 */
@@ -2546,7 +2525,6 @@ 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);
@@ -2568,7 +2546,6 @@ 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,
_
Patches currently in -mm which might be from senozhatsky@xxxxxxxxxxxx are
zram-sleepable-entry-locking.patch
zram-permit-preemption-with-active-compression-stream.patch
zram-remove-unused-crypto-include.patch
zram-remove-max_comp_streams-device-attr.patch
zram-remove-second-stage-of-handle-allocation.patch
zram-remove-writestall-zram_stats-member.patch
zram-limit-max-recompress-prio-to-num_active_comps.patch
zram-filter-out-recomp-targets-based-on-priority.patch
zram-rework-recompression-loop.patch
zsmalloc-rename-pool-lock.patch
zsmalloc-make-zspage-lock-preemptible.patch
zsmalloc-introduce-new-object-mapping-api.patch
zram-switch-to-new-zsmalloc-object-mapping-api.patch
zram-permit-reclaim-in-zstd-custom-allocator.patch
zram-do-not-leak-page-on-recompress_store-error-path.patch
zram-do-not-leak-page-on-writeback_store-error-path.patch
zram-add-might_sleep-to-zcomp-api.patch
zsmalloc-zram-there-be-preemption.patch
