From: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
To: Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>
Cc: Minchan Kim <minchan@kernel.org>,
Sergey Senozhatsky <sergey.senozhatsky@gmail.com>,
Andrew Morton <akpm@linux-foundation.org>,
linux-mm@kvack.org, linux-kernel@vger.kernel.org
Subject: Re: [RFC][PATCH 03/10] zsmalloc: introduce zs_can_compact() function
Date: Thu, 4 Jun 2015 12:31:18 +0900 [thread overview]
Message-ID: <20150604033118.GG1951@swordfish> (raw)
In-Reply-To: <20150604031514.GE1951@swordfish>
On (06/04/15 12:15), Sergey Senozhatsky wrote:
> I'm still thinking how good it should be.
>
> for automatic compaction we don't want to uselessly move objects between
> pages and I tend to think that it's better to compact less, than to waste
> more cpu cycless.
>
>
> on the other hand, this policy will miss cases like:
>
> -- free objects in class: 5 (free-objs class capacity)
> -- page1: inuse 2
> -- page2: inuse 2
> -- page3: inuse 3
> -- page4: inuse 2
>
> so total "insuse" is greater than free-objs class capacity. but, it's
> surely possible to compact this class. partial inuse summ <= free-objs class
> capacity (a partial summ is a ->inuse summ of any two of class pages:
> page1 + page2, page2 + page3, etc.).
>
> otoh, these partial sums will badly affect performance. may be for automatic
> compaction (the one that happens w/o user interaction) we can do zs_can_compact()
> and for manual compaction (the one that has been triggered by a user) we can
> old "full-scan".
>
> anyway, zs_can_compact() looks like something that we can optimize
> independently later.
>
so what I'm thinking of right now, is:
-- first do "if we have enough free objects to free at least one page"
check. compact if true.
-- if false, then we can do on a per-page basis
"if page->inuse <= class free-objs capacity" then compact it,
else select next almost_empty page.
here would be helpful to have pages ordered by ->inuse. but this
is far to expensive.
I have a patch that I will post later that introduces weak/partial
page ordering within fullness_list (really inexpensive: just one int
compare to add a page with a higher ->inuse to list head instead of
list tail).
-ss
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next prev parent reply other threads:[~2015-06-04 3:30 UTC|newest]
Thread overview: 30+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-05-29 15:05 [RFC][PATCH 00/10] zsmalloc auto-compaction Sergey Senozhatsky
2015-05-29 15:05 ` [RFC][PATCH 01/10] zsmalloc: drop unused variable `nr_to_migrate' Sergey Senozhatsky
2015-06-04 2:04 ` Minchan Kim
2015-06-04 2:10 ` Sergey Senozhatsky
2015-05-29 15:05 ` [RFC][PATCH 02/10] zsmalloc: always keep per-class stats Sergey Senozhatsky
2015-06-04 2:18 ` Minchan Kim
2015-06-04 2:34 ` Sergey Senozhatsky
2015-05-29 15:05 ` [RFC][PATCH 03/10] zsmalloc: introduce zs_can_compact() function Sergey Senozhatsky
2015-06-04 2:55 ` Minchan Kim
2015-06-04 3:15 ` Sergey Senozhatsky
2015-06-04 3:30 ` Minchan Kim
2015-06-04 3:42 ` Sergey Senozhatsky
2015-06-04 3:50 ` Minchan Kim
2015-06-04 4:19 ` Sergey Senozhatsky
2015-06-04 3:31 ` Sergey Senozhatsky [this message]
2015-05-29 15:05 ` [RFC][PATCH 04/10] zsmalloc: cosmetic compaction code adjustments Sergey Senozhatsky
2015-06-04 3:14 ` Minchan Kim
2015-05-29 15:05 ` [RFC][PATCH 05/10] zsmalloc: add `num_migrated' to zs_pool Sergey Senozhatsky
2015-05-29 15:05 ` [RFC][PATCH 06/10] zsmalloc: move compaction functions Sergey Senozhatsky
2015-05-29 15:05 ` [RFC][PATCH 07/10] zsmalloc: introduce auto-compact support Sergey Senozhatsky
2015-06-04 4:57 ` Minchan Kim
2015-06-04 5:30 ` Sergey Senozhatsky
2015-06-04 6:27 ` Minchan Kim
2015-06-04 7:04 ` Minchan Kim
2015-06-04 14:47 ` Sergey Senozhatsky
2015-06-04 7:28 ` Sergey Senozhatsky
2015-05-29 15:05 ` [RFC][PATCH 08/10] zsmalloc: export zs_pool `num_migrated' Sergey Senozhatsky
2015-05-29 15:05 ` [RFC][PATCH 09/10] zram: remove `num_migrated' from zram_stats Sergey Senozhatsky
2015-05-29 15:05 ` [RFC][PATCH 10/10] zsmalloc: lower ZS_ALMOST_FULL waterline Sergey Senozhatsky
2015-06-03 5:09 ` [RFC][PATCH 00/10] zsmalloc auto-compaction Sergey Senozhatsky
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