Re: [PATCH v1 15/29] virito-mem: document Sub Block Mode (SBM)

[Wei Yang]

On Mon, Oct 12, 2020 at 02:53:09PM +0200, David Hildenbrand wrote:
>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@xxxxxxxxxx>
>Cc: Jason Wang <jasowang@xxxxxxxxxx>
>Cc: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
>Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>

Reviewed-by: Wei Yang <richard.weiyang@xxxxxxxxxxxxxxxxx>

>---
> 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

-- 
Wei Yang
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