[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]
Message-ID: <20140915000058.GE2160@bbox>
Date: Mon, 15 Sep 2014 09:00:58 +0900
From: Minchan Kim <minchan@...nel.org>
To: Dan Streetman <ddstreet@...e.org>
Cc: Linux-MM <linux-mm@...ck.org>,
linux-kernel <linux-kernel@...r.kernel.org>,
Sergey Senozhatsky <sergey.senozhatsky@...il.com>,
Nitin Gupta <ngupta@...are.org>,
Seth Jennings <sjennings@...iantweb.net>,
Andrew Morton <akpm@...ux-foundation.org>,
Mel Gorman <mgorman@...e.de>
Subject: Re: [PATCH 00/10] implement zsmalloc shrinking
On Fri, Sep 12, 2014 at 01:05:11PM -0400, Dan Streetman wrote:
> On Fri, Sep 12, 2014 at 1:46 AM, Minchan Kim <minchan@...nel.org> wrote:
> > On Thu, Sep 11, 2014 at 04:53:51PM -0400, Dan Streetman wrote:
> >> Now that zswap can use zsmalloc as a storage pool via zpool, it will
> >> try to shrink its zsmalloc zs_pool once it reaches its max_pool_percent
> >> limit. These patches implement zsmalloc shrinking. The way the pool is
> >> shrunk is by finding a zspage and reclaiming it, by evicting each of its
> >> objects that is in use.
> >>
> >> Without these patches zswap, and any other future user of zpool/zsmalloc
> >> that attempts to shrink the zpool/zs_pool, will only get errors and will
> >> be unable to shrink its zpool/zs_pool. With the ability to shrink, zswap
> >> can keep the most recent compressed pages in memory.
> >>
> >> Note that the design of zsmalloc makes it impossible to actually find the
> >> LRU zspage, so each class and fullness group is searched in a round-robin
> >> method to find the next zspage to reclaim. Each fullness group orders its
> >> zspages in LRU order, so the oldest zspage is used for each fullness group.
> >>
> >
> > 1. Pz, Cc Mel who was strong against zswap with zsmalloc.
> > 2. I don't think LRU stuff should be in allocator layer. Exp, it's really
> > hard to work well in zsmalloc design.
>
> I didn't add any LRU - the existing fullness group LRU ordering is
> already there. And yes, the zsmalloc design prevents any real LRU
I don't think It's not LRU for reclaiming but just simple linked list for
finding free slot.
> ordering, beyond per-fullness-group LRU ordering.
Yes.
>
> > 3. If you want to add another writeback, make zswap writeback sane first.
> > current implemenation(zswap store -> zbud reclaim -> zswap writeback,
> > even) is really ugly.
>
> why what's wrong with that? how else can zbud/zsmalloc evict stored objects?
You can refer Mel's suggestion for zswap/zsmalloc and writeback problem.
http://www.spinics.net/lists/linux-mm/msg61601.html
http://lkml.iu.edu//hypermail/linux/kernel/1304.1/04334.html
I think LRU/writeback should be upper layer, not allocator itself.
Please, don't force every allocator to implement it for only zswap.
>
> > 4. Don't make zsmalloc complicated without any data(benefit, regression)
> > I will never ack if you don't give any number and real usecase.
>
> ok, i'll run performance tests then, but let me know if you see any
> technical problems with any of the patches before then.
>
> thanks!
>
> >
> >> ---
> >>
> >> This patch set applies to linux-next.
> >>
> >> Dan Streetman (10):
> >> zsmalloc: fix init_zspage free obj linking
> >> zsmalloc: add fullness group list for ZS_FULL zspages
> >> zsmalloc: always update lru ordering of each zspage
> >> zsmalloc: move zspage obj freeing to separate function
> >> zsmalloc: add atomic index to find zspage to reclaim
> >> zsmalloc: add zs_ops to zs_pool
> >> zsmalloc: add obj_handle_is_free()
> >> zsmalloc: add reclaim_zspage()
> >> zsmalloc: add zs_shrink()
> >> zsmalloc: implement zs_zpool_shrink() with zs_shrink()
> >>
> >> drivers/block/zram/zram_drv.c | 2 +-
> >> include/linux/zsmalloc.h | 7 +-
> >> mm/zsmalloc.c | 314 +++++++++++++++++++++++++++++++++++++-----
> >> 3 files changed, 290 insertions(+), 33 deletions(-)
> >>
> >> --
> >> 1.8.3.1
> >>
> >> --
> >> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> >> the body to majordomo@...ck.org. For more info on Linux MM,
> >> see: http://www.linux-mm.org/ .
> >> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
> >
> > --
> > Kind regards,
> > Minchan Kim
>
> --
> To unsubscribe, send a message with 'unsubscribe linux-mm' in
> the body to majordomo@...ck.org. For more info on Linux MM,
> see: http://www.linux-mm.org/ .
> Don't email: <a href=mailto:"dont@...ck.org"> email@...ck.org </a>
--
Kind regards,
Minchan Kim
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@...r.kernel.org
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists