Commit 3783689a authored by Minchan Kim's avatar Minchan Kim Committed by Linus Torvalds

zsmalloc: introduce zspage structure

We have squeezed meta data of zspage into first page's descriptor.  So,
to get meta data from subpage, we should get first page first of all.
But it makes trouble to implment page migration feature of zsmalloc
because any place where to get first page from subpage can be raced with
first page migration.  IOW, first page it got could be stale.  For
preventing it, I have tried several approahces but it made code
complicated so finally, I concluded to separate metadata from first
page.  Of course, it consumes more memory.  IOW, 16bytes per zspage on
32bit at the moment.  It means we lost 1% at *worst case*(40B/4096B)
which is not bad I think at the cost of maintenance.

Link: http://lkml.kernel.org/r/1464736881-24886-9-git-send-email-minchan@kernel.orgSigned-off-by: default avatarMinchan Kim <minchan@kernel.org>
Cc: Sergey Senozhatsky <sergey.senozhatsky@gmail.com>
Cc: Vlastimil Babka <vbabka@suse.cz>
Signed-off-by: default avatarAndrew Morton <akpm@linux-foundation.org>
Signed-off-by: default avatarLinus Torvalds <torvalds@linux-foundation.org>
parent bdb0af7c
......@@ -15,7 +15,6 @@
#include <linux/backing-dev.h>
#include <linux/sysctl.h>
#include <linux/sysfs.h>
#include <linux/balloon_compaction.h>
#include <linux/page-isolation.h>
#include <linux/kasan.h>
#include <linux/kthread.h>
......
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