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Date: Thu, 14 Aug 2014 11:09:05 -0400
From: Dan Streetman <ddstreet@...e.org>
To: Minchan Kim <minchan@...nel.org>
Cc: 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>, ds2horner@...il.com
Subject: Re: [PATCH 3/3] zram: add mem_used_max via sysfs
On Wed, Aug 13, 2014 at 9:12 PM, Minchan Kim <minchan@...nel.org> wrote:
> Normally, zram user can get maximum memory zsmalloc consumed via
> polling mem_used_total with sysfs in userspace.
>
> But it has a critical problem because user can miss peak memory
> usage during update interval of polling. For avoiding that,
> user should poll it frequently with mlocking to avoid delay
> when memory pressure is heavy so it would be handy if the
> kernel supports the function.
>
> This patch adds mem_used_max via sysfs.
>
> Signed-off-by: Minchan Kim <minchan@...nel.org>
> ---
> Documentation/blockdev/zram.txt | 1 +
> drivers/block/zram/zram_drv.c | 35 +++++++++++++++++++++++++++++++++--
> drivers/block/zram/zram_drv.h | 2 ++
> 3 files changed, 36 insertions(+), 2 deletions(-)
>
> diff --git a/Documentation/blockdev/zram.txt b/Documentation/blockdev/zram.txt
> index 9f239ff8c444..3b2247c2d4cf 100644
> --- a/Documentation/blockdev/zram.txt
> +++ b/Documentation/blockdev/zram.txt
> @@ -107,6 +107,7 @@ size of the disk when not in use so a huge zram is wasteful.
> orig_data_size
> compr_data_size
> mem_used_total
> + mem_used_max
>
> 8) Deactivate:
> swapoff /dev/zram0
> diff --git a/drivers/block/zram/zram_drv.c b/drivers/block/zram/zram_drv.c
> index b48a3d0e9031..311699f18bd5 100644
> --- a/drivers/block/zram/zram_drv.c
> +++ b/drivers/block/zram/zram_drv.c
> @@ -109,6 +109,30 @@ static ssize_t mem_used_total_show(struct device *dev,
> return scnprintf(buf, PAGE_SIZE, "%llu\n", val);
> }
>
> +static ssize_t mem_used_max_reset(struct device *dev,
> + struct device_attribute *attr, const char *buf, size_t len)
> +{
> + struct zram *zram = dev_to_zram(dev);
> +
> + down_write(&zram->init_lock);
> + zram->max_used_bytes = 0;
> + up_write(&zram->init_lock);
> + return len;
> +}
> +
> +static ssize_t mem_used_max_show(struct device *dev,
> + struct device_attribute *attr, char *buf)
> +{
> + u64 max_used_bytes;
> + struct zram *zram = dev_to_zram(dev);
> +
> + down_read(&zram->init_lock);
> + max_used_bytes = zram->max_used_bytes;
> + up_read(&zram->init_lock);
> +
> + return scnprintf(buf, PAGE_SIZE, "%llu\n", max_used_bytes);
> +}
> +
> static ssize_t max_comp_streams_show(struct device *dev,
> struct device_attribute *attr, char *buf)
> {
> @@ -474,6 +498,7 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> struct zram_meta *meta = zram->meta;
> struct zcomp_strm *zstrm;
> bool locked = false;
> + u64 total_bytes;
>
> page = bvec->bv_page;
> if (is_partial_io(bvec)) {
> @@ -543,8 +568,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> goto out;
> }
>
> - if (zram->limit_bytes &&
> - zs_get_total_size_bytes(meta->mem_pool) > zram->limit_bytes) {
> + total_bytes = zs_get_total_size_bytes(meta->mem_pool);
> + if (zram->limit_bytes && total_bytes > zram->limit_bytes) {
do you need to take the init_lock to read limit_bytes here? It could
be getting changed between these checks...
> zs_free(meta->mem_pool, handle);
> ret = -ENOMEM;
> goto out;
> @@ -578,6 +603,8 @@ static int zram_bvec_write(struct zram *zram, struct bio_vec *bvec, u32 index,
> /* Update stats */
> atomic64_add(clen, &zram->stats.compr_data_size);
> atomic64_inc(&zram->stats.pages_stored);
> +
> + zram->max_used_bytes = max(zram->max_used_bytes, total_bytes);
shouldn't max_used_bytes be atomic64_t? Or take the init_lock here?
> out:
> if (locked)
> zcomp_strm_release(zram->comp, zstrm);
> @@ -656,6 +683,7 @@ static void zram_reset_device(struct zram *zram, bool reset_capacity)
> down_write(&zram->init_lock);
>
> zram->limit_bytes = 0;
> + zram->max_used_bytes = 0;
>
> if (!init_done(zram)) {
> up_write(&zram->init_lock);
> @@ -897,6 +925,8 @@ 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_used_max, S_IRUGO | S_IWUSR, mem_used_max_show,
> + mem_used_max_reset);
> 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,
> @@ -927,6 +957,7 @@ 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_used_max.attr,
> &dev_attr_mem_limit.attr,
> &dev_attr_max_comp_streams.attr,
> &dev_attr_comp_algorithm.attr,
> diff --git a/drivers/block/zram/zram_drv.h b/drivers/block/zram/zram_drv.h
> index 086c51782e75..aca09b18fcbd 100644
> --- a/drivers/block/zram/zram_drv.h
> +++ b/drivers/block/zram/zram_drv.h
> @@ -111,6 +111,8 @@ struct zram {
> */
> u64 disksize; /* bytes */
> u64 limit_bytes;
> + u64 max_used_bytes;
> +
> int max_comp_streams;
> struct zram_stats stats;
> char compressor[10];
> --
> 2.0.0
>
--
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