From: David Hildenbrand <david@redhat.com>
To: linux-kernel@vger.kernel.org
Cc: virtualization@lists.linux-foundation.org, linux-mm@kvack.org,
linux-hyperv@vger.kernel.org, xen-devel@lists.xenproject.org,
David Hildenbrand <david@redhat.com>
Subject: [PATCH RFCv1 3/5] virtio-mem: try to merge "System RAM (virtio_mem)" resources
Date: Fri, 31 Jul 2020 11:18:36 +0200 [thread overview]
Message-ID: <20200731091838.7490-4-david@redhat.com> (raw)
In-Reply-To: <20200731091838.7490-1-david@redhat.com>
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.
Signed-off-by: David Hildenbrand <david@redhat.com>
---
drivers/virtio/virtio_mem.c | 14 ++++++++++++--
1 file changed, 12 insertions(+), 2 deletions(-)
diff --git a/drivers/virtio/virtio_mem.c b/drivers/virtio/virtio_mem.c
index f26f5f64ae822..2396a8d67875e 100644
--- a/drivers/virtio/virtio_mem.c
+++ b/drivers/virtio/virtio_mem.c
@@ -415,6 +415,7 @@ static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id)
{
const uint64_t addr = virtio_mem_mb_id_to_phys(mb_id);
int nid = vm->nid;
+ int rc;
if (nid == NUMA_NO_NODE)
nid = memory_add_physaddr_to_nid(addr);
@@ -431,8 +432,17 @@ static int virtio_mem_mb_add(struct virtio_mem *vm, unsigned long mb_id)
}
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);
+ rc = add_memory_driver_managed(nid, addr, memory_block_size_bytes(),
+ vm->resource_name);
+ if (!rc) {
+ /*
+ * Try to reduce the number of resources by merging them. The
+ * memory removal path will properly split them up again.
+ */
+ merge_child_mem_resources(vm->parent_resource,
+ vm->resource_name);
+ }
+ return rc;
}
/*
--
2.26.2
next prev parent reply other threads:[~2020-07-31 9:19 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-31 9:18 [PATCH RFCv1 0/5] mm/memory_hotplug: selective merging of memory resources David Hildenbrand
2020-07-31 9:18 ` [PATCH RFCv1 1/5] kernel/resource: make release_mem_region_adjustable() never fail David Hildenbrand
2020-07-31 9:18 ` [PATCH RFCv1 2/5] kernel/resource: merge_child_mem_resources() to merge memory resources after adding succeeded David Hildenbrand
2020-07-31 9:18 ` David Hildenbrand [this message]
2020-07-31 10:40 ` [PATCH RFCv1 3/5] virtio-mem: try to merge "System RAM (virtio_mem)" resources David Hildenbrand
2020-07-31 9:18 ` [PATCH RFCv1 4/5] xen/balloon: try to merge "System RAM" resources David Hildenbrand
2020-07-31 9:18 ` [PATCH RFCv1 5/5] hv_balloon:: " David Hildenbrand
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