Re: [PATCH v2] mm/zsmalloc: add statistics support

[Seth Jennings <sjennings@variantweb.net>]

On Tue, Dec 23, 2014 at 11:40:45AM +0900, Minchan Kim wrote:
> Hi Ganesh,
> 
> On Tue, Dec 23, 2014 at 10:26:12AM +0800, Ganesh Mahendran wrote:
> > Hello Minchan
> > 
> > 2014-12-20 10:25 GMT+08:00 Minchan Kim <minchan@kernel.org>:
> > > Hey Ganesh,
> > >
> > > On Sat, Dec 20, 2014 at 09:43:34AM +0800, Ganesh Mahendran wrote:
> > >> 2014-12-20 8:23 GMT+08:00 Minchan Kim <minchan@kernel.org>:
> > >> > On Fri, Dec 19, 2014 at 04:17:56PM -0800, Andrew Morton wrote:
> > >> >> On Sat, 20 Dec 2014 09:10:43 +0900 Minchan Kim <minchan@kernel.org> wrote:
> > >> >>
> > >> >> > > It involves rehashing a lengthy argument with Greg.
> > >> >> >
> > >> >> > Okay. Then, Ganesh,
> > >> >> > please add warn message about duplicaed name possibility althoug
> > >> >> > it's unlikely as it is.
> > >> >>
> > >> >> Oh, getting EEXIST is easy with this patch.  Just create and destroy a
> > >> >> pool 2^32 times and the counter wraps ;) It's hardly a serious issue
> > >> >> for a debugging patch.
> > >> >
> > >> > I meant that I wanted to change from index to name passed from caller like this
> > >> >
> > >> > zram:
> > >> >         zs_create_pool(GFP_NOIO | __GFP_HIGHMEM, zram->disk->first_minor);
> > >> >
> > >> > So, duplication should be rare. :)
> > >>
> > >> We still can not know whether the name is duplicated if we do not
> > >> change the debugfs API.
> > >> The API does not return the errno to us.
> > >>
> > >> How about just zsmalloc decides the name of the pool-id, like pool-x.
> > >> When the pool-id reaches
> > >> 0xffff.ffff, we print warn message about duplicated name, and stop
> > >> creating the debugfs entry
> > >> for the user.
> > >
> > > The idea is from the developer point of view to implement thing easy
> > > but my point is we should take care of user(ie, admin) rather than
> > > developer(ie, we).
> > 
> > Yes. I got it.
> > 
> > >
> > > For user, /sys/kernel/debug/zsmalloc/zram0 would be more
> > > straightforward and even it doesn't need zram to export
> > > /sys/block/zram0/pool-id.
> > 
> > BTW, If we add a new argument in zs_create_pool(). It seems we also need to
> > add argument in zs_zpool_create(). So, zpool/zswap/zbud will be
> > modified to support
> > the new API.
> > Is that acceptable?
> 
> I think it's doable.
> The zpool_create_pool has already zswap_zpool_type.
> Ccing maintainers for double check.

Late response, but fine by me.

Seth

> 
> Many thanks.
> 
> 
> > 
> > Thanks.
> > 
> > >
> > > Thanks.
> > >
> > >>
> > >> Thanks.
> > 
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> 
> -- 
> Kind regards,
> Minchan Kim
> 
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