From: David Hildenbrand <david@xxxxxxxxxx>
Subject: virtio-mem: try to merge system ram resources
virtio-mem adds memory in memory block granularity, to be able to remove
it in the same granularity again later, and to grow slowly on demand.
This, however, results in quite a lot of resources when adding a lot of
memory. Resources are effectively stored in a list-based tree. Having a
lot of resources not only wastes memory, it also makes traversing that
tree more expensive, and makes /proc/iomem explode in size (e.g.,
requiring kexec-tools to manually merge resources later when e.g., trying
to create a kdump header).
Before this patch, we get (/proc/iomem) when hotplugging 2G via virtio-mem
on x86-64:
[...]
100000000-13fffffff : System RAM
140000000-33fffffff : virtio0
140000000-147ffffff : System RAM (virtio_mem)
148000000-14fffffff : System RAM (virtio_mem)
150000000-157ffffff : System RAM (virtio_mem)
158000000-15fffffff : System RAM (virtio_mem)
160000000-167ffffff : System RAM (virtio_mem)
168000000-16fffffff : System RAM (virtio_mem)
170000000-177ffffff : System RAM (virtio_mem)
178000000-17fffffff : System RAM (virtio_mem)
180000000-187ffffff : System RAM (virtio_mem)
188000000-18fffffff : System RAM (virtio_mem)
190000000-197ffffff : System RAM (virtio_mem)
198000000-19fffffff : System RAM (virtio_mem)
1a0000000-1a7ffffff : System RAM (virtio_mem)
1a8000000-1afffffff : System RAM (virtio_mem)
1b0000000-1b7ffffff : System RAM (virtio_mem)
1b8000000-1bfffffff : System RAM (virtio_mem)
3280000000-32ffffffff : PCI Bus 0000:00
With this patch, we get (/proc/iomem):
[...]
fffc0000-ffffffff : Reserved
100000000-13fffffff : System RAM
140000000-33fffffff : virtio0
140000000-1bfffffff : System RAM (virtio_mem)
3280000000-32ffffffff : PCI Bus 0000:00
Of course, with more hotplugged memory, it gets worse. When unplugging
memory blocks again, try_remove_memory() (via offline_and_remove_memory())
will properly split the resource up again.
Link: https://lkml.kernel.org/r/20200911103459.10306-7-david@xxxxxxxxxx
Signed-off-by: David Hildenbrand <david@xxxxxxxxxx>
Reviewed-by: Pankaj Gupta <pankaj.gupta.linux@xxxxxxxxx>
Cc: Michal Hocko <mhocko@xxxxxxxx>
Cc: Dan Williams <dan.j.williams@xxxxxxxxx>
Cc: Michael S. Tsirkin <mst@xxxxxxxxxx>
Cc: Jason Wang <jasowang@xxxxxxxxxx>
Cc: Baoquan He <bhe@xxxxxxxxxx>
Cc: Wei Yang <richardw.yang@xxxxxxxxxxxxxxx>
Cc: Anton Blanchard <anton@xxxxxxxxxx>
Cc: Ard Biesheuvel <ardb@xxxxxxxxxx>
Cc: Benjamin Herrenschmidt <benh@xxxxxxxxxxxxxxxxxxx>
Cc: Boris Ostrovsky <boris.ostrovsky@xxxxxxxxxx>
Cc: Christian Borntraeger <borntraeger@xxxxxxxxxx>
Cc: Dave Jiang <dave.jiang@xxxxxxxxx>
Cc: Eric Biederman <ebiederm@xxxxxxxxxxxx>
Cc: Greg Kroah-Hartman <gregkh@xxxxxxxxxxxxxxxxxxx>
Cc: Haiyang Zhang <haiyangz@xxxxxxxxxxxxx>
Cc: Heiko Carstens <hca@xxxxxxxxxxxxx>
Cc: Jason Gunthorpe <jgg@xxxxxxxx>
Cc: Juergen Gross <jgross@xxxxxxxx>
Cc: Julien Grall <julien@xxxxxxx>
Cc: Kees Cook <keescook@xxxxxxxxxxxx>
Cc: "K. Y. Srinivasan" <kys@xxxxxxxxxxxxx>
Cc: Len Brown <lenb@xxxxxxxxxx>
Cc: Leonardo Bras <leobras.c@xxxxxxxxx>
Cc: Libor Pechacek <lpechacek@xxxxxxx>
Cc: Michael Ellerman <mpe@xxxxxxxxxxxxxx>
Cc: Nathan Lynch <nathanl@xxxxxxxxxxxxx>
Cc: "Oliver O'Halloran" <oohall@xxxxxxxxx>
Cc: Paul Mackerras <paulus@xxxxxxxxx>
Cc: Pingfan Liu <kernelfans@xxxxxxxxx>
Cc: "Rafael J. Wysocki" <rjw@xxxxxxxxxxxxx>
Cc: Roger Pau Monné <roger.pau@xxxxxxxxxx>
Cc: Stefano Stabellini <sstabellini@xxxxxxxxxx>
Cc: Stephen Hemminger <sthemmin@xxxxxxxxxxxxx>
Cc: Thomas Gleixner <tglx@xxxxxxxxxxxxx>
Cc: Vasily Gorbik <gor@xxxxxxxxxxxxx>
Cc: Vishal Verma <vishal.l.verma@xxxxxxxxx>
Cc: Wei Liu <wei.liu@xxxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
drivers/virtio/virtio_mem.c | 3 ++-
1 file changed, 2 insertions(+), 1 deletion(-)
--- a/drivers/virtio/virtio_mem.c~virtio-mem-try-to-merge-system-ram-resources
+++ a/drivers/virtio/virtio_mem.c
@@ -424,7 +424,8 @@ static int virtio_mem_mb_add(struct virt
dev_dbg(&vm->vdev->dev, "adding memory block: %lu\n", mb_id);
return add_memory_driver_managed(nid, addr, memory_block_size_bytes(),
- vm->resource_name, MHP_NONE);
+ vm->resource_name,
+ MEMHP_MERGE_RESOURCE);
}
/*
_
