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Message-ID: <CALZtONAqvXgEE93Q_ya+MPbP+1-BTZZB9k4fOofTg-Qzdpjb7g@mail.gmail.com>
Date: Fri, 22 Aug 2014 14:47:21 -0400
From: Dan Streetman <ddstreet@...e.org>
To: David Horner <ds2horner@...il.com>
Cc: Minchan Kim <minchan@...nel.org>,
Andrew Morton <akpm@...ux-foundation.org>,
Linux-MM <linux-mm@...ck.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Jerome Marchand <jmarchan@...hat.com>, juno.choi@....com,
seungho1.park@....com, Luigi Semenzato <semenzato@...gle.com>,
Nitin Gupta <ngupta@...are.org>,
Seth Jennings <sjennings@...iantweb.net>
Subject: Re: [PATCH v4 3/4] zram: zram memory size limitation
On Fri, Aug 22, 2014 at 6:55 AM, David Horner <ds2horner@...il.com> wrote:
> On Thu, Aug 21, 2014 at 8:42 PM, Minchan Kim <minchan@...nel.org> 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.
Yes by "default" I meant the initial value.
>
> 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.
I'm not sure of the specifics of memparse, but if it returns 0 for
non-numeric strings (which i assume it does, since there's no method
for reporting errors) I agree that should return -EINVAL instead of
clearing the mem_limit.
>
>>
>> Signed-off-by: Minchan Kim <minchan@...nel.org>
>> ---
>> 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@...nel.org>
>> +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.
>
>> + 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
>>
--
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