[RFC][PATCHv2 3/8] zsmalloc: lower ZS_ALMOST_FULL waterline

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From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Minchan Kim <minchan@kernel.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: [RFC][PATCHv2 3/8] zsmalloc: lower ZS_ALMOST_FULL waterline
Date: Fri,  5 Jun 2015 21:03:53 +0900	[thread overview]
Message-ID: <1433505838-23058-4-git-send-email-sergey.senozhatsky@gmail.com> (raw)
In-Reply-To: <1433505838-23058-1-git-send-email-sergey.senozhatsky@gmail.com>

get_fullness_group() considers 3/4 full pages as almost empty.
That, unfortunately, marks as ALMOST_EMPTY pages that we would
probably like to keep in ALMOST_FULL lists.

ALMOST_EMPTY:
[..]
  inuse: 3 max_objects: 4
  inuse: 5 max_objects: 7
  inuse: 5 max_objects: 7
  inuse: 2 max_objects: 3
[..]

For "inuse: 5 max_objexts: 7" ALMOST_EMPTY page, for example,
it'll take 2 obj_malloc to make the page FULL and 5 obj_free to
make it EMPTY. Compaction selects ALMOST_EMPTY pages as source
pages, which can result in extra object moves.

In other words, from compaction point of view, it makes more
sense to fill this page, rather than drain it.

Decrease ALMOST_FULL waterline to 2/3 of max capacity; which is,
of course, still imperfect, but can shorten compaction
execution time.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 mm/zsmalloc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index cd37bda..b94e281 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -198,7 +198,7 @@ static int zs_size_classes;
  *
  * (see: fix_fullness_group())
  */
-static const int fullness_threshold_frac = 4;
+static const int fullness_threshold_frac = 3;
 
 struct size_class {
 	/*
@@ -633,7 +633,7 @@ static enum fullness_group get_fullness_group(struct page *page)
 		fg = ZS_EMPTY;
 	else if (inuse == max_objects)
 		fg = ZS_FULL;
-	else if (inuse <= 3 * max_objects / fullness_threshold_frac)
+	else if (inuse <= 2 * max_objects / fullness_threshold_frac)
 		fg = ZS_ALMOST_EMPTY;
 	else
 		fg = ZS_ALMOST_FULL;
-- 
2.4.2.387.gf86f31a

WARNING: multiple messages have this Message-ID (diff)

From: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
To: Andrew Morton <akpm@linux-foundation.org>,
	Minchan Kim <minchan@kernel.org>
Cc: linux-mm@kvack.org, linux-kernel@vger.kernel.org,
	Sergey Senozhatsky <sergey.senozhatsky.work@gmail.com>,
	Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Subject: [RFC][PATCHv2 3/8] zsmalloc: lower ZS_ALMOST_FULL waterline
Date: Fri,  5 Jun 2015 21:03:53 +0900	[thread overview]
Message-ID: <1433505838-23058-4-git-send-email-sergey.senozhatsky@gmail.com> (raw)
In-Reply-To: <1433505838-23058-1-git-send-email-sergey.senozhatsky@gmail.com>

get_fullness_group() considers 3/4 full pages as almost empty.
That, unfortunately, marks as ALMOST_EMPTY pages that we would
probably like to keep in ALMOST_FULL lists.

ALMOST_EMPTY:
[..]
  inuse: 3 max_objects: 4
  inuse: 5 max_objects: 7
  inuse: 5 max_objects: 7
  inuse: 2 max_objects: 3
[..]

For "inuse: 5 max_objexts: 7" ALMOST_EMPTY page, for example,
it'll take 2 obj_malloc to make the page FULL and 5 obj_free to
make it EMPTY. Compaction selects ALMOST_EMPTY pages as source
pages, which can result in extra object moves.

In other words, from compaction point of view, it makes more
sense to fill this page, rather than drain it.

Decrease ALMOST_FULL waterline to 2/3 of max capacity; which is,
of course, still imperfect, but can shorten compaction
execution time.

Signed-off-by: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
---
 mm/zsmalloc.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/mm/zsmalloc.c b/mm/zsmalloc.c
index cd37bda..b94e281 100644
--- a/mm/zsmalloc.c
+++ b/mm/zsmalloc.c
@@ -198,7 +198,7 @@ static int zs_size_classes;
  *
  * (see: fix_fullness_group())
  */
-static const int fullness_threshold_frac = 4;
+static const int fullness_threshold_frac = 3;
 
 struct size_class {
 	/*
@@ -633,7 +633,7 @@ static enum fullness_group get_fullness_group(struct page *page)
 		fg = ZS_EMPTY;
 	else if (inuse == max_objects)
 		fg = ZS_FULL;
-	else if (inuse <= 3 * max_objects / fullness_threshold_frac)
+	else if (inuse <= 2 * max_objects / fullness_threshold_frac)
 		fg = ZS_ALMOST_EMPTY;
 	else
 		fg = ZS_ALMOST_FULL;
-- 
2.4.2.387.gf86f31a

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next prev parent reply	other threads:[~2015-06-05 12:05 UTC|newest]

Thread overview: 52+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2015-06-05 12:03 [RFC][PATCHv2 0/8] introduce automatic pool compaction Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 1/8] zsmalloc: drop unused variable `nr_to_migrate' Sergey Senozhatsky
2015-06-05 12:03   ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 2/8] zsmalloc: partial page ordering within a fullness_list Sergey Senozhatsky
2015-06-05 12:03   ` Sergey Senozhatsky
2015-06-16 13:19   ` Minchan Kim
2015-06-16 13:19     ` Minchan Kim
2015-06-16 14:30     ` Sergey Senozhatsky
2015-06-16 14:30       ` Sergey Senozhatsky
2015-06-05 12:03 ` Sergey Senozhatsky [this message]
2015-06-05 12:03   ` [RFC][PATCHv2 3/8] zsmalloc: lower ZS_ALMOST_FULL waterline Sergey Senozhatsky
2015-06-16 13:37   ` Minchan Kim
2015-06-16 13:37     ` Minchan Kim
2015-06-16 14:35     ` Sergey Senozhatsky
2015-06-16 14:35       ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 4/8] zsmalloc: always keep per-class stats Sergey Senozhatsky
2015-06-05 12:03   ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 5/8] zsmalloc: introduce zs_can_compact() function Sergey Senozhatsky
2015-06-05 12:03   ` Sergey Senozhatsky
2015-06-16 14:19   ` Minchan Kim
2015-06-16 14:19     ` Minchan Kim
2015-06-16 14:41     ` Sergey Senozhatsky
2015-06-16 14:41       ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 6/8] zsmalloc: cosmetic compaction code adjustments Sergey Senozhatsky
2015-06-05 12:03   ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 7/8] zsmalloc/zram: move `num_migrated' to zs_pool Sergey Senozhatsky
2015-06-05 12:03   ` Sergey Senozhatsky
2015-06-05 12:03 ` [RFC][PATCHv2 8/8] zsmalloc: register a shrinker to trigger auto-compaction Sergey Senozhatsky
2015-06-05 12:03   ` Sergey Senozhatsky
2015-06-16 14:47   ` Minchan Kim
2015-06-16 14:47     ` Minchan Kim
2015-06-16 15:45     ` Sergey Senozhatsky
2015-06-16 15:45       ` Sergey Senozhatsky
2015-06-18  1:50       ` Minchan Kim
2015-06-18  1:50         ` Minchan Kim
2015-06-18  2:41         ` Sergey Senozhatsky
2015-06-18  2:41           ` Sergey Senozhatsky
2015-06-18  3:01           ` Sergey Senozhatsky
2015-06-18  3:01             ` Sergey Senozhatsky
2015-06-18  3:46             ` Minchan Kim
2015-06-18  3:46               ` Minchan Kim
2015-06-18  3:39           ` Minchan Kim
2015-06-18  3:39             ` Minchan Kim
2015-06-18  3:58             ` Sergey Senozhatsky
2015-06-18  3:58               ` Sergey Senozhatsky
2015-06-17  7:11     ` Sergey Senozhatsky
2015-06-17  7:11       ` Sergey Senozhatsky
2015-06-10  0:04 ` [RFC][PATCHv2 0/8] introduce automatic pool compaction Minchan Kim
2015-06-10  0:04   ` Minchan Kim
2015-06-10  0:07   ` Sergey Senozhatsky
2015-06-10  0:07     ` Sergey Senozhatsky

find likely ancestor, descendant, or conflicting patches for this message:
dfblob:cd37bda dfblob:cd37bda dfblob:b94e281 dfblob:b94e281
	(help)

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