The patch titled
Subject: zram: writeback throttle
has been added to the -mm tree. Its filename is
zram-writeback-throttle.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/zram-writeback-throttle.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/zram-writeback-throttle.patch
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*** Remember to use Documentation/process/submit-checklist.rst when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Minchan Kim <minchan@xxxxxxxxxx>
Subject: zram: writeback throttle
On small memory systems there are lots of write IOs so if we use a flash
device as swap there would be serious flash wearout. To overcome this
problem, system developers need to design a write limitation strategy to
guarantee flash health for the entire product life.
This patch creates a new knob "writeback_limit" on zram. With that, if
the current writeback IO count (/sys/block/zramX/io_stat) exceeds the
limitation, zram stops further writeback until the admin can reset the
limit.
Link: http://lkml.kernel.org/r/20181127055429.251614-8-minchan@xxxxxxxxxx
Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
Cc: Joey Pabalinas <joeypabalinas@xxxxxxxxx>
Cc: Sergey Senozhatsky <sergey.senozhatsky.work@xxxxxxxxx>
Cc: <stable@xxxxxxxxxxxxxxx> [4.14+]
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
Documentation/ABI/testing/sysfs-block-zram | 9 +++
Documentation/blockdev/zram.txt | 2
drivers/block/zram/zram_drv.c | 47 ++++++++++++++++++-
drivers/block/zram/zram_drv.h | 2
4 files changed, 59 insertions(+), 1 deletion(-)
--- a/Documentation/ABI/testing/sysfs-block-zram~zram-writeback-throttle
+++ a/Documentation/ABI/testing/sysfs-block-zram
@@ -121,3 +121,12 @@ Description:
The bd_stat file is read-only and represents backing device's
statistics (bd_count, bd_reads, bd_writes) in a format
similar to block layer statistics file format.
+
+What: /sys/block/zram<id>/writeback_limit
+Date: November 2018
+Contact: Minchan Kim <minchan@xxxxxxxxxx>
+Description:
+ The writeback_limit file is read-write and specifies the maximum
+ amount of writeback ZRAM can do. The limit could be changed
+ in run time and "0" means disable the limit.
+ No limit is the initial state.
--- a/Documentation/blockdev/zram.txt~zram-writeback-throttle
+++ a/Documentation/blockdev/zram.txt
@@ -164,6 +164,8 @@ reset WO trigger device r
mem_used_max WO reset the `mem_used_max' counter (see later)
mem_limit WO specifies the maximum amount of memory ZRAM can use
to store the compressed data
+writeback_limit WO specifies the maximum amount of write IO zram can
+ write out to backing device as 4KB unit
max_comp_streams RW the number of possible concurrent compress operations
comp_algorithm RW show and change the compression algorithm
compact WO trigger memory compaction
--- a/drivers/block/zram/zram_drv.c~zram-writeback-throttle
+++ a/drivers/block/zram/zram_drv.c
@@ -330,6 +330,40 @@ next:
}
#ifdef CONFIG_ZRAM_WRITEBACK
+
+static ssize_t writeback_limit_store(struct device *dev,
+ struct device_attribute *attr, const char *buf, size_t len)
+{
+ struct zram *zram = dev_to_zram(dev);
+ u64 val;
+ ssize_t ret = -EINVAL;
+
+ if (kstrtoull(buf, 10, &val))
+ return ret;
+
+ down_read(&zram->init_lock);
+ atomic64_set(&zram->stats.bd_wb_limit, val);
+ if (val == 0 || val > atomic64_read(&zram->stats.bd_writes))
+ zram->stop_writeback = false;
+ up_read(&zram->init_lock);
+ ret = len;
+
+ return ret;
+}
+
+static ssize_t writeback_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 = atomic64_read(&zram->stats.bd_wb_limit);
+ up_read(&zram->init_lock);
+
+ return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
+}
+
static void reset_bdev(struct zram *zram)
{
struct block_device *bdev;
@@ -571,6 +605,7 @@ static ssize_t writeback_store(struct de
char mode_buf[8];
unsigned long mode = -1UL;
unsigned long blk_idx = 0;
+ u64 wb_count, wb_limit;
sz = strscpy(mode_buf, buf, sizeof(mode_buf));
if (sz <= 0)
@@ -612,6 +647,11 @@ static ssize_t writeback_store(struct de
bvec.bv_len = PAGE_SIZE;
bvec.bv_offset = 0;
+ if (zram->stop_writeback) {
+ ret = -EIO;
+ break;
+ }
+
if (!blk_idx) {
blk_idx = alloc_block_bdev(zram);
if (!blk_idx) {
@@ -670,7 +710,7 @@ static ssize_t writeback_store(struct de
continue;
}
- atomic64_inc(&zram->stats.bd_writes);
+ wb_count = atomic64_inc_return(&zram->stats.bd_writes);
/*
* We released zram_slot_lock so need to check if the slot was
* changed. If there is freeing for the slot, we can catch it
@@ -694,6 +734,9 @@ static ssize_t writeback_store(struct de
zram_set_element(zram, index, blk_idx);
blk_idx = 0;
atomic64_inc(&zram->stats.pages_stored);
+ wb_limit = atomic64_read(&zram->stats.bd_wb_limit);
+ if (wb_limit != 0 && wb_count >= wb_limit)
+ zram->stop_writeback = true;
next:
zram_slot_unlock(zram, index);
}
@@ -1767,6 +1810,7 @@ static DEVICE_ATTR_RW(comp_algorithm);
#ifdef CONFIG_ZRAM_WRITEBACK
static DEVICE_ATTR_RW(backing_dev);
static DEVICE_ATTR_WO(writeback);
+static DEVICE_ATTR_RW(writeback_limit);
#endif
static struct attribute *zram_disk_attrs[] = {
@@ -1782,6 +1826,7 @@ static struct attribute *zram_disk_attrs
#ifdef CONFIG_ZRAM_WRITEBACK
&dev_attr_backing_dev.attr,
&dev_attr_writeback.attr,
+ &dev_attr_writeback_limit.attr,
#endif
&dev_attr_io_stat.attr,
&dev_attr_mm_stat.attr,
--- a/drivers/block/zram/zram_drv.h~zram-writeback-throttle
+++ a/drivers/block/zram/zram_drv.h
@@ -86,6 +86,7 @@ struct zram_stats {
atomic64_t bd_count; /* no. of pages in backing device */
atomic64_t bd_reads; /* no. of reads from backing device */
atomic64_t bd_writes; /* no. of writes from backing device */
+ atomic64_t bd_wb_limit; /* writeback limit of backing device */
#endif
};
@@ -113,6 +114,7 @@ struct zram {
*/
bool claim; /* Protected by bdev->bd_mutex */
struct file *backing_dev;
+ bool stop_writeback;
#ifdef CONFIG_ZRAM_WRITEBACK
struct block_device *bdev;
unsigned int old_block_size;
_
Patches currently in -mm which might be from minchan@xxxxxxxxxx are
zram-fix-lockdep-warning-of-free-block-handling.patch
zram-fix-double-free-backing-device.patch
zram-refactoring-flags-and-writeback-stuff.patch
zram-introduce-zram_idle-flag.patch
zram-support-idle-huge-page-writeback.patch
zram-add-bd_stat-statistics.patch
zram-writeback-throttle.patch
