Re: [RFC 0/3] zram memory control enhance

[Minchan Kim <minchan@kernel.org>]

On Wed, Aug 13, 2014 at 10:34:22AM -0500, Seth Jennings wrote:
> On Tue, Aug 05, 2014 at 05:02:00PM +0900, Minchan Kim wrote:
> > Notice! It's RFC. I didn't test at all but wanted to hear opinion
> > during merge window when it's really busy time for Andrew so we could
> > use the slack time to discuss without hurting him. ;-)
> > 
> > Patch 1 is to move pages_allocated in zsmalloc from size_class to zs_pool
> > so zs_get_total_size_bytes of zsmalloc would be faster than old.
> > zs_get_total_size_bytes could be used next patches frequently.
> > 
> > Patch 2 adds new feature which exports how many of bytes zsmalloc consumes
> > during testing workload. Normally, before fixing the zram's disksize
> > we have tested various workload and wanted to how many of bytes zram
> > consumed.
> > For it, we could poll mem_used_total of zram in userspace but the problem is
> > when memory pressure is severe and heavy swap out happens suddenly then
> > heavy swapin or exist while polling interval of user space is a few second,
> > it could miss max memory size zram had consumed easily.
> > With lack of information, user can set wrong disksize of zram so the result
> > is OOM. So this patch adds max_mem_used for zram and zsmalloc supports it
> > 
> > Patch 3 is to limit zram memory consumption. Now, zram has no bound for
> > memory usage so it could consume up all of system memory. It makes system
> > memory control for platform hard so I have heard the feature several time.
> > 
> > Feedback is welcome!
> 
> One thing you might consider doing is moving zram to use the new zpool
> API.  That way, when making changes that effect the zsmalloc API,
> consideration for zpool, and by extension, zpool users like zswap are
> also taken into account.

Now, it's rather overkill for zram.

> 
> Seth
> 
> > 
> > Minchan Kim (3):
> >   zsmalloc: move pages_allocated to zs_pool
> >   zsmalloc/zram: add zs_get_max_size_bytes and use it in zram
> >   zram: limit memory size for zram
> > 
> >  Documentation/blockdev/zram.txt |  2 ++
> >  drivers/block/zram/zram_drv.c   | 58 +++++++++++++++++++++++++++++++++++++++++
> >  drivers/block/zram/zram_drv.h   |  1 +
> >  include/linux/zsmalloc.h        |  1 +
> >  mm/zsmalloc.c                   | 50 +++++++++++++++++++++++++----------
> >  5 files changed, 98 insertions(+), 14 deletions(-)
> > 
> > -- 
> > 2.0.0
> > 
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-- 
Kind regards,
Minchan Kim