[PATCH v1 15/29] virito-mem: document Sub Block Mode (SBM)
From: David Hildenbrand <hidden>
Date: 2020-10-12 12:55:41
Also in:
linux-mm, lkml
Subsystem:
the rest, virtio core, virtio mem driver · Maintainers:
Linus Torvalds, "Michael S. Tsirkin", Jason Wang, David Hildenbrand
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 Device Block Mode (DBM). Cc: "Michael S. Tsirkin" <mst@redhat.com> Cc: Jason Wang <jasowang@redhat.com> Cc: Pankaj Gupta <pankaj.gupta.linux@gmail.com> Signed-off-by: David Hildenbrand <redacted> --- drivers/virtio/virtio_mem.c | 15 +++++++++++++++ 1 file changed, 15 insertions(+)
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index faeb759687fe..fd8685673fe4 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c@@ -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,
--
2.26.2
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