> From: Minchan Kim [mailto:minchan@xxxxxxxxxx] > Subject: Re: zsmalloc defrag (Was: [PATCH] mm: remove compressed copy from zram in-memory) > > Hi Seth, > > On Tue, Apr 09, 2013 at 03:52:36PM -0500, Seth Jennings wrote: > > On 04/08/2013 08:36 PM, Minchan Kim wrote: > > > On Tue, Apr 09, 2013 at 10:27:19AM +0900, Minchan Kim wrote: > > >> Hi Dan, > > >> > > >> On Mon, Apr 08, 2013 at 09:32:38AM -0700, Dan Magenheimer wrote: > > >>>> From: Minchan Kim [mailto:minchan@xxxxxxxxxx] > > >>>> Sent: Monday, April 08, 2013 12:01 AM > > >>>> Subject: [PATCH] mm: remove compressed copy from zram in-memory > > >>> > > >>> (patch removed) > > >>> > > >>>> Fragment ratio is almost same but memory consumption and compile time > > >>>> is better. I am working to add defragment function of zsmalloc. > > >>> > > >>> Hi Minchan -- > > >>> > > >>> I would be very interested in your design thoughts on > > >>> how you plan to add defragmentation for zsmalloc. In > > >> > > >> What I can say now about is only just a word "Compaction". > > >> As you know, zsmalloc has a transparent handle so we can do whatever > > >> under user. Of course, there is a tradeoff between performance > > >> and memory efficiency. I'm biased to latter for embedded usecase. > > >> > > >> And I might post it because as you know well, zsmalloc > > > > > > Incomplete sentense, > > > > > > I might not post it until promoting zsmalloc because as you know well, > > > zsmalloc/zram's all new stuffs are blocked into staging tree. > > > Even if we could add it into staging, as you know well, staging is where > > > every mm guys ignore so we end up needing another round to promote it. sigh. > > > > Yes. The lack of compaction/defragmentation support in zsmalloc has not > > been raised as an obstacle to mainline acceptance so I think we should > > wait to add new features to a yet-to-be accepted codebase. > > > > Also, I think this feature is more important to zram than it is to > > zswap/zcache as they can do writeback to free zpages. In other words, > > the fragmentation is a transient issue for zswap/zcache since writeback > > to the swap device is possible. > > Other benefit derived from compaction work is that we can pick a zpage > from zspage and move it into somewhere. It means core mm could control > pages in zsmalloc freely. I'm not sure I understand which is why I'd like to learn more about your proposed design. Are you suggesting that core mm would periodically call zsmalloc-compaction and see what pages get freed? I'm hoping for more control than that. More good discussion for next week! Dan -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@xxxxxxxxx. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: <a href