Received-SPF: pass (google.com: domain of linux-kernel-owner@vger.kernel.org designates 2620:137:e000::1:20 as permitted sender) client-ip=2620:137:e000::1:20;
Sender: Minchan Kim <minchan.kim@gmail.com>
Date:   Fri, 4 Nov 2022 09:34:07 -0700
From:   Minchan Kim <minchan@kernel.org>
To:     Sergey Senozhatsky <senozhatsky@chromium.org>
Cc:     Andrew Morton <akpm@linux-foundation.org>,
        Nitin Gupta <ngupta@vflare.org>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
Subject: Re: [PATCHv4 2/9] zram: Add recompression algorithm sysfs knob
Message-ID: <Y2U+/xQBwR3MPygL@google.com>
References: <20221018045533.2396670-1-senozhatsky@chromium.org>
 <20221018045533.2396670-3-senozhatsky@chromium.org>
 <Y2LP0OWF/WTnkSne@google.com>
 <Y2Mv4l+V9iCv9EMg@google.com>
 <Y2Ptq1GZISCD7Mor@google.com>
 <Y2SEkzKSWx2iQzLl@google.com>
MIME-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <Y2SEkzKSWx2iQzLl@google.com>
Precedence: bulk

On Fri, Nov 04, 2022 at 12:18:43PM +0900, Sergey Senozhatsky wrote:
> On (22/11/03 09:34), Minchan Kim wrote:
> > > > My point is that we don't need to implement it atm but makes the
> > > > interface to open the possibility for future extension.
> > > > 
> > > > What do you think?
> > > 
> > > So, as far as I understand, we don't have reason to add remove_recomp_algo
> > > right now. And existing recomp_algo does not enforce any particular format,
> > > it can be extended. Right now we accept "$name" but can do something like
> > > "$name:$priority". The only thing that we probably need to do is rename
> > > recomp_algo to either add_recomp_algo or register_recomp_algo?
> > 
> > Yeah, I like the name and priority format.
> > 
> > Only question is how we could support algorithm selection change
> > under considering multiple secondary algorithms.
> 
> So what I was thinking about, and I'm still in the mental model that
> re-compression is a user-space event, just like writeback, extension
> of recompress sysfs knob with "algo_index" (or something similar) which
> will mirror algorithm priority.
> 
> Example:
> 
> Configure 2 alternative algos, with priority 1 and 2
> 
> 	echo "name=lz4 priority=1" > recomp_algo
> 	echo "name=lz5 priority=2" > recomp_algo
> 
> Recompress pages using algo 1 and algo 2
> 
> 	echo "type=huge threshold=3000 algo_idx=1" > recompress
> 	echo "type=idle threshold=2000 algo_idx=2" > recompress
> 
> Maybe we can even pass algo name instead of idx.

Let's use name rather than index.