Re: [PATCH v4 3/4] zram: zram memory size limitation
From: Minchan Kim
Date: Sun Aug 24 2014 - 19:55:48 EST
Hello David,
On Fri, Aug 22, 2014 at 06:55:38AM -0400, David Horner wrote:
> On Thu, Aug 21, 2014 at 8:42 PM, Minchan Kim <minchan@xxxxxxxxxx> wrote:
> > Since zram has no control feature to limit memory usage,
> > it makes hard to manage system memrory.
> >
> > This patch adds new knob "mem_limit" via sysfs to set up the
> > a limit so that zram could fail allocation once it reaches
> > the limit.
> >
> > In addition, user could change the limit in runtime so that
> > he could manage the memory more dynamically.
> >
> - Default is no limit so it doesn't break old behavior.
> + Initial state is no limit so it doesn't break old behavior.
>
> I understand your previous post now.
>
> I was saying that setting to either a null value or garbage
> (which is interpreted as zero by memparse(buf, NULL);)
> removes the limit.
>
> I think this is "surprise" behaviour and rather the null case should
> return -EINVAL
> The test below should be "good enough" though not catching all garbage.
Thanks for suggesting but as I said, it should be fixed in memparse itself,
not caller if it is really problem so I don't want to touch it in this
patchset. It's not critical for adding the feature.
>
> >
> > Signed-off-by: Minchan Kim <minchan@xxxxxxxxxx>
> > ---
> > Documentation/ABI/testing/sysfs-block-zram | 10 ++++++++
> > Documentation/blockdev/zram.txt | 24 ++++++++++++++---
> > drivers/block/zram/zram_drv.c | 41 ++++++++++++++++++++++++++++++
> > drivers/block/zram/zram_drv.h | 5 ++++
> > 4 files changed, 76 insertions(+), 4 deletions(-)
> >
> > diff --git a/Documentation/ABI/testing/sysfs-block-zram b/Documentation/ABI/testing/sysfs-block-zram
> > index 70ec992514d0..b8c779d64968 100644
> > --- a/Documentation/ABI/testing/sysfs-block-zram
> > +++ b/Documentation/ABI/testing/sysfs-block-zram
> > @@ -119,3 +119,13 @@ Description:
> > efficiency can be calculated using compr_data_size and this
> > statistic.
> > Unit: bytes
> > +
> > +What: /sys/block/zram<id>/mem_limit
> > +Date: August 2014
> > +Contact: Minchan Kim <minchan@xxxxxxxxxx>
> > +Description:
> > + The mem_limit file is read/write and specifies the amount
> > + of memory to be able to consume memory to store store
> > + compressed data. The limit could be changed in run time
> > - and "0" is default which means disable the limit.
> > + and "0" means disable the limit. No limit is the initial state.
>
> there should be no default in the API.
Thanks.
>
> > + Unit: bytes
> > diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
> > index 0595c3f56ccf..82c6a41116db 100644
> > --- a/Documentation/blockdev/zram.txt
> > +++ b/Documentation/blockdev/zram.txt
> > @@ -74,14 +74,30 @@ 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.
> >
> > -5) Activate:
> > +5) Set memory limit: Optional
> > + Set memory limit by writing the value to sysfs node 'mem_limit'.
> > + The value can be either in bytes or you can use mem suffixes.
> > + In addition, you could change the value in runtime.
> > + Examples:
> > + # limit /dev/zram0 with 50MB memory
> > + echo $((50*1024*1024)) > /sys/block/zram0/mem_limit
> > +
> > + # Using mem suffixes
> > + echo 256K > /sys/block/zram0/mem_limit
> > + echo 512M > /sys/block/zram0/mem_limit
> > + echo 1G > /sys/block/zram0/mem_limit
> > +
> > + # To disable memory limit
> > + echo 0 > /sys/block/zram0/mem_limit
> > +
> > +6) Activate:
> > mkswap /dev/zram0
> > swapon /dev/zram0
> >
> > mkfs.ext4 /dev/zram1
> > mount /dev/zram1 /tmp
> >
> > -6) Stats:
> > +7) Stats:
> > Per-device statistics are exported as various nodes under
> > /sys/block/zram<id>/
> > disksize
> > @@ -96,11 +112,11 @@ size of the disk when not in use so a huge zram is wasteful.
> > compr_data_size
> > mem_used_total
> >
> > -7) Deactivate:
> > +8) Deactivate:
> > swapoff /dev/zram0
> > umount /dev/zram1
> >
> > -8) Reset:
> > +9) Reset:
> > Write any positive value to 'reset' sysfs node
> > echo 1 > /sys/block/zram0/reset
> > echo 1 > /sys/block/zram1/reset
> > diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> > index f0b8b30a7128..370c355eb127 100644
> > --- a/drivers/block/zram/zram_drv.c
> > +++ b/drivers/block/zram/zram_drv.c
> > @@ -122,6 +122,33 @@ static ssize_t max_comp_streams_show(struct device *dev,
> > return scnprintf(buf, PAGE_SIZE, "%d\n", val);
> > }
> >
> > +static ssize_t mem_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 = zram->limit_pages;
> > + up_read(&zram->init_lock);
> > +
> > + return scnprintf(buf, PAGE_SIZE, "%llu\n", val << PAGE_SHIFT);
> > +}
> > +
> > +static ssize_t mem_limit_store(struct device *dev,
> > + struct device_attribute *attr, const char *buf, size_t len)
> > +{
> > + u64 limit;
> > + struct zram *zram = dev_to_zram(dev);
> > +
> > + limit = memparse(buf, NULL);
>
> if (limit = 0 && buf != "0")
> return -EINVAL
>
> > + down_write(&zram->init_lock);
> > + zram->limit_pages = PAGE_ALIGN(limit) >> PAGE_SHIFT;
> > + up_write(&zram->init_lock);
> > +
> > + return len;
> > +}
> > +
> > static ssize_t max_comp_streams_store(struct device *dev,
> > struct device_attribute *attr, const char *buf, size_t len)
> > {
> > @@ -513,6 +540,14 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> > ret = -ENOMEM;
> > goto out;
> > }
> > +
> > + if (zram->limit_pages &&
> > + zs_get_total_pages(meta->mem_pool) > zram->limit_pages) {
> > + zs_free(meta->mem_pool, handle);
> > + ret = -ENOMEM;
> > + goto out;
> > + }
> > +
> > cmem = zs_map_object(meta->mem_pool, handle, ZS_MM_WO);
> >
> > if ((clen == PAGE_SIZE) && !is_partial_io(bvec)) {
> > @@ -617,6 +652,9 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
> > struct zram_meta *meta;
> >
> > down_write(&zram->init_lock);
> > +
> > + zram->limit_pages = 0;
> > +
> > if (!init_done(zram)) {
> > up_write(&zram->init_lock);
> > return;
> > @@ -857,6 +895,8 @@ static DEVICE_ATTR(initstate, S_IRUGO, initstate_show, NULL);
> > static DEVICE_ATTR(reset, S_IWUSR, NULL, reset_store);
> > 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(mem_limit, S_IRUGO | S_IWUSR, mem_limit_show,
> > + mem_limit_store);
> > 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,
> > @@ -885,6 +925,7 @@ static struct attribute *zram_disk_attrs[] = {
> > &dev_attr_orig_data_size.attr,
> > &dev_attr_compr_data_size.attr,
> > &dev_attr_mem_used_total.attr,
> > + &dev_attr_mem_limit.attr,
> > &dev_attr_max_comp_streams.attr,
> > &dev_attr_comp_algorithm.attr,
> > NULL,
> > diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> > index e0f725c87cc6..b7aa9c21553f 100644
> > --- a/drivers/block/zram/zram_drv.h
> > +++ b/drivers/block/zram/zram_drv.h
> > @@ -112,6 +112,11 @@ struct zram {
> > u64 disksize; /* bytes */
> > int max_comp_streams;
> > struct zram_stats stats;
> > + /*
> > + * the number of pages zram can consume for storing compressed data
> > + */
> > + unsigned long limit_pages;
> > +
> > char compressor[10];
> > };
> > #endif
> > --
> > 2.0.0
> >
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@xxxxxxxxxx For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>
--
Kind regards,
Minchan Kim
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/