zsmalloc: adjust ZS_ALMOST_FULL

Curretly, zsmalloc regards a zspage as ZS_ALMOST_EMPTY if the zspage has
under 1/4 used objects(ie, fullness_threshold_frac).  It could make result
in loose packing since zsmalloc migrates only ZS_ALMOST_EMPTY zspage out.

This patch changes the rule so that zsmalloc makes zspage which has above
3/4 used object ZS_ALMOST_FULL so it could make tight packing.

Signed-off-by: Minchan Kim <[email protected]>
Cc: Juneho Choi <[email protected]>
Cc: Gunho Lee <[email protected]>
Cc: Luigi Semenzato <[email protected]>
Cc: Dan Streetman <[email protected]>
Cc: Seth Jennings <[email protected]>
Cc: Nitin Gupta <[email protected]>
Cc: Jerome Marchand <[email protected]>
Cc: Sergey Senozhatsky <[email protected]>
Cc: Joonsoo Kim <[email protected]>
Cc: Mel Gorman <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>
Signed-off-by: Linus Torvalds <[email protected]>

mm/zsmalloc.c

@@ -480,7 +480,7 @@ static enum fullness_group get_fullness_group(struct page *page)
 		fg = ZS_EMPTY;
 	else if (inuse == max_objects)
 		fg = ZS_FULL;
-	else if (inuse <= max_objects / fullness_threshold_frac)
+	else if (inuse <= 3 * max_objects / fullness_threshold_frac)
 		fg = ZS_ALMOST_EMPTY;
 	else
 		fg = ZS_ALMOST_FULL;