Commit d5614944 authored by David Hildenbrand's avatar David Hildenbrand Committed by Michael S. Tsirkin
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virito-mem: document Sub Block Mode (SBM) 



Let's add some documentation for the current mode - Sub Block Mode (SBM) -
to prepare for a new mode - Big Block Mode (BBM).

Follow-up patches will properly factor out the existing Sub Block Mode
(SBM) and implement Big Block Mode (BBM).

Reviewed-by: default avatarWei Yang <richard.weiyang@linux.alibaba.com>
Reviewed-by: default avatarPankaj Gupta <pankaj.gupta.linux@gmail.com>
Cc: "Michael S. Tsirkin" <mst@redhat.com>
Cc: Jason Wang <jasowang@redhat.com>
Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com>
Signed-off-by: default avatarDavid Hildenbrand <david@redhat.com>
Link: https://lore.kernel.org/r/20201112133815.13332-18-david@redhat.com


Signed-off-by: default avatarMichael S. Tsirkin <mst@redhat.com>
parent 98ff9f94

drivers/virtio/virtio_mem.c

+15 −0
Original line number Diff line number Diff line
@@ -27,6 +27,21 @@ static bool unplug_online = true; 
module_param(unplug_online, bool, 0644);

MODULE_PARM_DESC(unplug_online, "Try to unplug online memory");



/*

 * virtio-mem currently supports the following modes of operation:

 *

 * * Sub Block Mode (SBM): A Linux memory block spans 1..X subblocks (SB). The

 *   size of a Sub Block (SB) is determined based on the device block size, the

 *   pageblock size, and the maximum allocation granularity of the buddy.

 *   Subblocks within a Linux memory block might either be plugged or unplugged.

 *   Memory is added/removed to Linux MM in Linux memory block granularity.

 *

 * User space / core MM (auto onlining) is responsible for onlining added

 * Linux memory blocks - and for selecting a zone. Linux Memory Blocks are

 * always onlined separately, and all memory within a Linux memory block is

 * onlined to the same zone - virtio-mem relies on this behavior.

 */



enum virtio_mem_mb_state {

	/* Unplugged, not added to Linux. Can be reused later. */

	VIRTIO_MEM_MB_STATE_UNUSED = 0,