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>,
"Andrew Morton" <akpm@linux-foundation.org>,
"Ard Biesheuvel" <ardb@kernel.org>,
"Boris Ostrovsky" <boris.ostrovsky@oracle.com>,
"Dan Williams" <dan.j.williams@intel.com>,
"Haiyang Zhang" <haiyangz@microsoft.com>,
"Jason Gunthorpe" <jgg@ziepe.ca>,
"Juergen Gross" <jgross@suse.com>,
"Julien Grall" <julien@xen.org>,
"Kees Cook" <keescook@chromium.org>,
"K. Y. Srinivasan" <kys@microsoft.com>,
"Michal Hocko" <mhocko@suse.com>,
"Roger Pau Monné" <roger.pau@citrix.com>,
"Stefano Stabellini" <sstabellini@kernel.org>,
"Stephen Hemminger" <sthemmin@microsoft.com>,
"Thomas Gleixner" <tglx@linutronix.de>,
"Wei Liu" <wei.liu@kernel.org>,
"Wei Yang" <richardw.yang@linux.intel.com>
Subject: [PATCH RFCv1 0/5] mm/memory_hotplug: selective merging of memory resources
Date: Fri, 31 Jul 2020 11:18:33 +0200 [thread overview]
Message-ID: <20200731091838.7490-1-david@redhat.com> (raw)
Some add_memory*() users add memory in small, contiguous memory blocks.
Examples include virtio-mem, hyper-v balloon, and the XEN balloon.
This can quickly result in a lot of memory resources, whereby the actual
resource boundaries are not of interest (e.g., it might be relevant for
DIMMs, exposed via /proc/iomem to user space). We really want to merge
added resources in this scenario where possible.
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 when creating a kdump header. The
current kexec-tools resource count limit does not allow more than ~100GB
of memory with a memory block size of 128MB on x86-64).
Let's allow to selectively merge resources, speciyfing a parent node and
a resource idendifier string. The memory unplug path will properly split
up merged resources again.
Patch #3 contains a /proc/iomem example. Only tested with virtio-mem.
Note: This gets the job done and is comparably simple. More complicated
approaches would require introducing IORESOURCE_MERGEABLE and extending our
add_memory*() interfaces with a flag, specifying that merging after adding
succeeded is acceptable. I'd like to avoid that complexity and code churn
for now.
David Hildenbrand (5):
kernel/resource: make release_mem_region_adjustable() never fail
kernel/resource: merge_child_mem_resources() to merge memory resources
after adding succeeded
virtio-mem: try to merge "System RAM (virtio_mem)" resources
xen/balloon: try to merge "System RAM" resources
hv_balloon:: try to merge "System RAM" resources
drivers/hv/hv_balloon.c | 3 ++
drivers/virtio/virtio_mem.c | 14 ++++-
drivers/xen/balloon.c | 4 ++
include/linux/ioport.h | 7 ++-
kernel/resource.c | 105 ++++++++++++++++++++++++++++--------
mm/memory_hotplug.c | 22 +-------
6 files changed, 109 insertions(+), 46 deletions(-)
--
2.26.2
next reply other threads:[~2020-07-31 9:18 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-07-31 9:18 David Hildenbrand [this message]
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 ` [PATCH RFCv1 3/5] virtio-mem: try to merge "System RAM (virtio_mem)" resources David Hildenbrand
2020-07-31 10:40 ` 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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