linux-kernel - Re: [PATCH v4 2/4] zram: implement deduplication in zram

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Date:   Wed, 26 Apr 2017 15:04:28 +0900
From:   Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>
To:     Joonsoo Kim <js1304@...il.com>
Cc:     Sergey Senozhatsky <sergey.senozhatsky.work@...il.com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Minchan Kim <minchan@...nel.org>,
        Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
        linux-kernel@...r.kernel.org, kernel-team@....com
Subject: Re: [PATCH v4 2/4] zram: implement deduplication in zram

On (04/26/17 14:59), Joonsoo Kim wrote:
> On Wed, Apr 26, 2017 at 11:37:18AM +0900, Sergey Senozhatsky wrote:
> > On (04/26/17 09:52), js1304@...il.com wrote:
> > [..]
> > >  struct zram_entry {
> > > +	struct rb_node rb_node;
> > > +	u32 len;
> > > +	u32 checksum;
> > > +	unsigned long refcount;
> > 
> > 	use refcount_t? what do you think?
> 
> We don't need atomic operation for refcount but refcount_t does.
> API of refcount_t provides additional guarantee that refcount will not
> overflow but I'm not sure that this overhead is needed here.

refcount_t has some additional debugging features which probably
could be helpful one day, but not necessarily needed in current
zram_dedup implementation, agree. asked just in case.

	-ss