Minchan Kim ca4909acf4 zsmalloc: move it under mm ... (cherry pick from bcf1647d08) This patch moves zsmalloc under mm directory. Before that, description will explain why we have needed custom allocator. Zsmalloc is a new slab-based memory allocator for storing compressed pages. It is designed for low fragmentation and high allocation success rate on large object, but <= PAGE_SIZE allocations. zsmalloc differs from the kernel slab allocator in two primary ways to achieve these design goals. zsmalloc never requires high order page allocations to back slabs, or "size classes" in zsmalloc terms. Instead it allows multiple single-order pages to be stitched together into a "zspage" which backs the slab. This allows for higher allocation success rate under memory pressure. Also, zsmalloc allows objects to span page boundaries within the zspage. This allows for lower fragmentation than could be had with the kernel slab allocator for objects between PAGE_SIZE/2 and PAGE_SIZE. With the kernel slab allocator, if a page compresses to 60% of it original size, the memory savings gained through compression is lost in fragmentation because another object of the same size can't be stored in the leftover space. This ability to span pages results in zsmalloc allocations not being directly addressable by the user. The user is given an non-dereferencable handle in response to an allocation request. That handle must be mapped, using zs_map_object(), which returns a pointer to the mapped region that can be used. The mapping is necessary since the object data may reside in two different noncontigious pages. The zsmalloc fulfills the allocation needs for zram perfectly [sjenning@linux.vnet.ibm.com: borrow Seth's quote] Signed-off-by: Minchan Kim <minchan@kernel.org> Acked-by: Nitin Gupta <ngupta@vflare.org> Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@oracle.com> Cc: Bob Liu <bob.liu@oracle.com> Cc: Greg Kroah-Hartman <gregkh@linuxfoundation.org> Cc: Hugh Dickins <hughd@google.com> Cc: Jens Axboe <axboe@kernel.dk> Cc: Luigi Semenzato <semenzato@google.com> Cc: Mel Gorman <mgorman@suse.de> Cc: Pekka Enberg <penberg@kernel.org> Cc: Rik van Riel <riel@redhat.com> Cc: Seth Jennings <sjenning@linux.vnet.ibm.com> Signed-off-by: Andrew Morton <akpm@linux-foundation.org> Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org> Bug: 24810447 Change-Id: I7b7923baeb9989e002523c66696e4a98fb357c46		2018-01-01 21:26:37 +03:00
..
acpi	ACPICA: Tables: Fix an issue that FACS initialization is performed twice	2015-10-22 09:20:07 +08:00
asm-generic	Merge remote-tracking branch 'stable/linux-3.4.y' into lineage-15.1	2017-12-27 17:13:15 +03:00
crypto	Merge remote-tracking branch 'stable/linux-3.4.y' into lineage-15.1	2017-12-27 17:13:15 +03:00
drm	Merge remote-tracking branch 'stable/linux-3.4.y' into lineage-15.1	2017-12-27 17:13:15 +03:00
keys	KEYS: Permit in-place link replacement in keyring list	2016-10-29 23:12:12 +08:00
linux	zsmalloc: move it under mm	2018-01-01 21:26:37 +03:00
math-emu
media	Merge remote-tracking branch 'stable/linux-3.4.y' into lineage-15.1	2017-12-27 17:13:15 +03:00
misc
mtd
net	Merge remote-tracking branch 'stable/linux-3.4.y' into lineage-15.1	2017-12-27 17:13:15 +03:00
pcmcia
rdma
rxrpc
scsi	SCSI: add 1024 max sectors black list flag	2015-09-18 09:20:33 +08:00
sound	Merge remote-tracking branch 'stable/linux-3.4.y' into lineage-15.1	2017-12-27 17:13:15 +03:00
target	Merge remote-tracking branch 'stable/linux-3.4.y' into lineage-15.1	2017-12-27 17:13:15 +03:00
trace	Merge remote-tracking branch 'stable/linux-3.4.y' into lineage-15.1	2017-12-27 17:13:15 +03:00
video
xen	xen: Add RING_COPY_REQUEST()	2016-10-26 23:15:39 +08:00
Kbuild