Re: [PATCH v4 7/7] zram: writeback throttle
On (12/03/18 15:02), Sergey Senozhatsky wrote: > Seems like I misread writeback_limit_store() a bit. > > So, if I want to, say, let only 10M of writteback pages, I need to > do > > echo 0 > writeback_limit > echo 10M > writeback_limit_store// memparse format is for > // simplicity only; I know > // it should be in 4K units. > > every day. How about dropping the "echo 0" and ->stop_writeback? Ah, this breaks the unlimited writeback. So, nevermind my comment. -ss
Re: [PATCH v4 7/7] zram: writeback throttle
On (12/03/18 15:02), Sergey Senozhatsky wrote: > Seems like I misread writeback_limit_store() a bit. > > So, if I want to, say, let only 10M of writteback pages, I need to > do > > echo 0 > writeback_limit > echo 10M > writeback_limit_store// memparse format is for > // simplicity only; I know > // it should be in 4K units. > > every day. How about dropping the "echo 0" and ->stop_writeback? Ah, this breaks the unlimited writeback. So, nevermind my comment. -ss
Re: [PATCH v4 7/7] zram: writeback throttle
On (12/03/18 14:50), Sergey Senozhatsky wrote:
> On (12/03/18 11:40), Minchan Kim wrote:
> [..]
> > + down_read(>init_lock);
> > + atomic64_set(>stats.bd_wb_limit, val);
> > + if (val == 0)
> > + zram->stop_writeback = false;
> > + up_read(>init_lock);
>
> [..]
>
> > + if (zram->stop_writeback) {
> > + ret = -EIO;
> > + break;
> > + }
> > +
> > if (!blk_idx) {
> > blk_idx = alloc_block_bdev(zram);
> > if (!blk_idx) {
> > @@ -694,6 +732,11 @@ static ssize_t writeback_store(struct device *dev,
> > zram_set_element(zram, index, blk_idx);
> > blk_idx = 0;
> > atomic64_inc(>stats.pages_stored);
> > + if (atomic64_add_unless(>stats.bd_wb_limit,
> > + -1 << (PAGE_SHIFT - 12), 0)) {
> > + if (atomic64_read(>stats.bd_wb_limit) == 0)
> > + zram->stop_writeback = true;
> > + }
>
> Do we need ->stop_writeback? It should be identical to
>
> atomic64_read(>stats.bd_wb_limit) == 0
Seems like I misread writeback_limit_store() a bit.
So, if I want to, say, let only 10M of writteback pages, I need to
do
echo 0 > writeback_limit
echo 10M > writeback_limit_store// memparse format is for
// simplicity only; I know
// it should be in 4K units.
every day. How about dropping the "echo 0" and ->stop_writeback?
So then we can just do
echo 10M > writeback_limit_store
every day: if we have ->bd_wb_limit budget then we writeback,
otherwise we don't.
-ss
Re: [PATCH v4 7/7] zram: writeback throttle
On (12/03/18 14:50), Sergey Senozhatsky wrote:
> On (12/03/18 11:40), Minchan Kim wrote:
> [..]
> > + down_read(>init_lock);
> > + atomic64_set(>stats.bd_wb_limit, val);
> > + if (val == 0)
> > + zram->stop_writeback = false;
> > + up_read(>init_lock);
>
> [..]
>
> > + if (zram->stop_writeback) {
> > + ret = -EIO;
> > + break;
> > + }
> > +
> > if (!blk_idx) {
> > blk_idx = alloc_block_bdev(zram);
> > if (!blk_idx) {
> > @@ -694,6 +732,11 @@ static ssize_t writeback_store(struct device *dev,
> > zram_set_element(zram, index, blk_idx);
> > blk_idx = 0;
> > atomic64_inc(>stats.pages_stored);
> > + if (atomic64_add_unless(>stats.bd_wb_limit,
> > + -1 << (PAGE_SHIFT - 12), 0)) {
> > + if (atomic64_read(>stats.bd_wb_limit) == 0)
> > + zram->stop_writeback = true;
> > + }
>
> Do we need ->stop_writeback? It should be identical to
>
> atomic64_read(>stats.bd_wb_limit) == 0
Seems like I misread writeback_limit_store() a bit.
So, if I want to, say, let only 10M of writteback pages, I need to
do
echo 0 > writeback_limit
echo 10M > writeback_limit_store// memparse format is for
// simplicity only; I know
// it should be in 4K units.
every day. How about dropping the "echo 0" and ->stop_writeback?
So then we can just do
echo 10M > writeback_limit_store
every day: if we have ->bd_wb_limit budget then we writeback,
otherwise we don't.
-ss
Re: [PATCH v4 7/7] zram: writeback throttle
On (12/03/18 11:40), Minchan Kim wrote:
[..]
> + down_read(>init_lock);
> + atomic64_set(>stats.bd_wb_limit, val);
> + if (val == 0)
> + zram->stop_writeback = false;
> + up_read(>init_lock);
[..]
> + if (zram->stop_writeback) {
> + ret = -EIO;
> + break;
> + }
> +
> if (!blk_idx) {
> blk_idx = alloc_block_bdev(zram);
> if (!blk_idx) {
> @@ -694,6 +732,11 @@ static ssize_t writeback_store(struct device *dev,
> zram_set_element(zram, index, blk_idx);
> blk_idx = 0;
> atomic64_inc(>stats.pages_stored);
> + if (atomic64_add_unless(>stats.bd_wb_limit,
> + -1 << (PAGE_SHIFT - 12), 0)) {
> + if (atomic64_read(>stats.bd_wb_limit) == 0)
> + zram->stop_writeback = true;
> + }
Do we need ->stop_writeback? It should be identical to
atomic64_read(>stats.bd_wb_limit) == 0
Otherwise, looks good!
-ss
Re: [PATCH v4 7/7] zram: writeback throttle
On (12/03/18 11:40), Minchan Kim wrote:
[..]
> + down_read(>init_lock);
> + atomic64_set(>stats.bd_wb_limit, val);
> + if (val == 0)
> + zram->stop_writeback = false;
> + up_read(>init_lock);
[..]
> + if (zram->stop_writeback) {
> + ret = -EIO;
> + break;
> + }
> +
> if (!blk_idx) {
> blk_idx = alloc_block_bdev(zram);
> if (!blk_idx) {
> @@ -694,6 +732,11 @@ static ssize_t writeback_store(struct device *dev,
> zram_set_element(zram, index, blk_idx);
> blk_idx = 0;
> atomic64_inc(>stats.pages_stored);
> + if (atomic64_add_unless(>stats.bd_wb_limit,
> + -1 << (PAGE_SHIFT - 12), 0)) {
> + if (atomic64_read(>stats.bd_wb_limit) == 0)
> + zram->stop_writeback = true;
> + }
Do we need ->stop_writeback? It should be identical to
atomic64_read(>stats.bd_wb_limit) == 0
Otherwise, looks good!
-ss
[PATCH v4 7/7] zram: writeback throttle
If there are lots of write IO with flash device, it could have a wearout problem of storage. To overcome the problem, admin needs to design write limitation to guarantee flash health for entire product life. This patch creates a new knob "writeback_limit" on zram. writeback_limit's default value is 0 so that it doesn't limit any writeback. If admin want to measure writeback count in a certain period, he could know it via /sys/block/zram0/bd_stat's 3rd column. If admin want to limit writeback as per-day 400M, he could do it like below. MB_SHIFT=20 4K_SHIFT=12 echo $((400<>4K_SHIFT)) > \ /sys/block/zram0/writeback_limit. If admin want to allow further write again, he could do it like below echo 0 > /sys/block/zram0/writeback_limit If admin want to see remaining writeback budget, cat /sys/block/zram0/writeback_limit The writeback_limit count will reset whenever you reset zram(e.g., system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of writeback happened until you reset the zram to allocate extra writeback budget in next setting is user's job. Signed-off-by: Minchan Kim --- I removed Reviewed-by from Sergey and Joey because I modified interface since they had reviewed. Documentation/ABI/testing/sysfs-block-zram | 9 Documentation/blockdev/zram.txt| 31 + drivers/block/zram/zram_drv.c | 52 -- drivers/block/zram/zram_drv.h | 2 + 4 files changed, 91 insertions(+), 3 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram index 65fc33b2f53b..9d2339a485c8 100644 --- a/Documentation/ABI/testing/sysfs-block-zram +++ b/Documentation/ABI/testing/sysfs-block-zram @@ -121,3 +121,12 @@ Contact: Minchan Kim 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/writeback_limit +Date: November 2018 +Contact: Minchan Kim +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. diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 906df97527a7..436c5e98e1b6 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -164,6 +164,8 @@ reset WOtrigger device reset mem_used_max WOreset the `mem_used_max' counter (see later) mem_limit WOspecifies the maximum amount of memory ZRAM can use to store the compressed data +writeback_limit WOspecifies the maximum amount of write IO zram can + write out to backing device as 4KB unit max_comp_streams RWthe number of possible concurrent compress operations comp_algorithmRWshow and change the compression algorithm compact WOtrigger memory compaction @@ -275,6 +277,35 @@ Admin can request writeback of those idle pages at right timing via With the command, zram writeback idle pages from memory to the storage. +If there are lots of write IO with flash device, potentially, it has +flash wearout problem so that admin needs to design write limitation +to guarantee storage health for entire product life. +To overcome the concern, zram supports "writeback_limit". +The "writeback_limit"'s default value is 0 so that it doesn't limit +any writeback. If admin want to measure writeback count in a certain +period, he could know it via /sys/block/zram0/bd_stat's 3rd column. + +If admin want to limit writeback as per-day 400M, he could do it +like below. + +MB_SHIFT=20 +4K_SHIFT=12 +echo $((400<>4K_SHIFT)) > \ + /sys/block/zram0/writeback_limit. + +If admin want to allow further write again, he could do it like below + +echo 0 > /sys/block/zram0/writeback_limit + +If admin want to see remaining writeback budget since he set, + +cat /sys/block/zram0/writeback_limit + +The writeback_limit count will reset whenever you reset zram(e.g., +system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of +writeback happened until you reset the zram to allocate extra writeback +budget in next setting is user's job. + = memory tracking With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index f1832fa3ba41..33c5cc879f24 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -330,6 +330,39 @@ static ssize_t idle_store(struct device *dev, } #ifdef CONFIG_ZRAM_WRITEBACK +static ssize_t writeback_limit_store(struct device *dev, +
[PATCH v4 7/7] zram: writeback throttle
If there are lots of write IO with flash device, it could have a wearout problem of storage. To overcome the problem, admin needs to design write limitation to guarantee flash health for entire product life. This patch creates a new knob "writeback_limit" on zram. writeback_limit's default value is 0 so that it doesn't limit any writeback. If admin want to measure writeback count in a certain period, he could know it via /sys/block/zram0/bd_stat's 3rd column. If admin want to limit writeback as per-day 400M, he could do it like below. MB_SHIFT=20 4K_SHIFT=12 echo $((400<>4K_SHIFT)) > \ /sys/block/zram0/writeback_limit. If admin want to allow further write again, he could do it like below echo 0 > /sys/block/zram0/writeback_limit If admin want to see remaining writeback budget, cat /sys/block/zram0/writeback_limit The writeback_limit count will reset whenever you reset zram(e.g., system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of writeback happened until you reset the zram to allocate extra writeback budget in next setting is user's job. Signed-off-by: Minchan Kim --- I removed Reviewed-by from Sergey and Joey because I modified interface since they had reviewed. Documentation/ABI/testing/sysfs-block-zram | 9 Documentation/blockdev/zram.txt| 31 + drivers/block/zram/zram_drv.c | 52 -- drivers/block/zram/zram_drv.h | 2 + 4 files changed, 91 insertions(+), 3 deletions(-) diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram index 65fc33b2f53b..9d2339a485c8 100644 --- a/Documentation/ABI/testing/sysfs-block-zram +++ b/Documentation/ABI/testing/sysfs-block-zram @@ -121,3 +121,12 @@ Contact: Minchan Kim 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/writeback_limit +Date: November 2018 +Contact: Minchan Kim +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. diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt index 906df97527a7..436c5e98e1b6 100644 --- a/Documentation/blockdev/zram.txt +++ b/Documentation/blockdev/zram.txt @@ -164,6 +164,8 @@ reset WOtrigger device reset mem_used_max WOreset the `mem_used_max' counter (see later) mem_limit WOspecifies the maximum amount of memory ZRAM can use to store the compressed data +writeback_limit WOspecifies the maximum amount of write IO zram can + write out to backing device as 4KB unit max_comp_streams RWthe number of possible concurrent compress operations comp_algorithmRWshow and change the compression algorithm compact WOtrigger memory compaction @@ -275,6 +277,35 @@ Admin can request writeback of those idle pages at right timing via With the command, zram writeback idle pages from memory to the storage. +If there are lots of write IO with flash device, potentially, it has +flash wearout problem so that admin needs to design write limitation +to guarantee storage health for entire product life. +To overcome the concern, zram supports "writeback_limit". +The "writeback_limit"'s default value is 0 so that it doesn't limit +any writeback. If admin want to measure writeback count in a certain +period, he could know it via /sys/block/zram0/bd_stat's 3rd column. + +If admin want to limit writeback as per-day 400M, he could do it +like below. + +MB_SHIFT=20 +4K_SHIFT=12 +echo $((400<>4K_SHIFT)) > \ + /sys/block/zram0/writeback_limit. + +If admin want to allow further write again, he could do it like below + +echo 0 > /sys/block/zram0/writeback_limit + +If admin want to see remaining writeback budget since he set, + +cat /sys/block/zram0/writeback_limit + +The writeback_limit count will reset whenever you reset zram(e.g., +system reboot, echo 1 > /sys/block/zramX/reset) so keeping how many of +writeback happened until you reset the zram to allocate extra writeback +budget in next setting is user's job. + = memory tracking With CONFIG_ZRAM_MEMORY_TRACKING, user can know information of the diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c index f1832fa3ba41..33c5cc879f24 100644 --- a/drivers/block/zram/zram_drv.c +++ b/drivers/block/zram/zram_drv.c @@ -330,6 +330,39 @@ static ssize_t idle_store(struct device *dev, } #ifdef CONFIG_ZRAM_WRITEBACK +static ssize_t writeback_limit_store(struct device *dev, +
