From: David Hildenbrand <david@redhat.com>
To: Vishal Verma <vishal.l.verma@intel.com>,
Andrew Morton <akpm@linux-foundation.org>,
Oscar Salvador <osalvador@suse.de>,
Dan Williams <dan.j.williams@intel.com>,
Dave Jiang <dave.jiang@intel.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
nvdimm@lists.linux.dev, linux-cxl@vger.kernel.org,
Huang Ying <ying.huang@intel.com>,
Dave Hansen <dave.hansen@linux.intel.com>,
"Aneesh Kumar K.V" <aneesh.kumar@linux.ibm.com>,
Michal Hocko <mhocko@suse.com>,
Jonathan Cameron <Jonathan.Cameron@Huawei.com>,
Jeff Moyer <jmoyer@redhat.com>
Subject: Re: [PATCH v6 2/3] mm/memory_hotplug: split memmap_on_memory requests across memblocks
Date: Tue, 17 Oct 2023 16:49:38 +0200 [thread overview]
Message-ID: <f2720382-5374-4b8f-ad3c-f3f13e4a3767@redhat.com> (raw)
In-Reply-To: <20231016-vv-kmem_memmap-v6-2-078f0d3c0371@intel.com>
On 17.10.23 07:44, Vishal Verma wrote:
> The MHP_MEMMAP_ON_MEMORY flag for hotplugged memory is restricted to
> 'memblock_size' chunks of memory being added. Adding a larger span of
> memory precludes memmap_on_memory semantics.
>
> For users of hotplug such as kmem, large amounts of memory might get
> added from the CXL subsystem. In some cases, this amount may exceed the
> available 'main memory' to store the memmap for the memory being added.
> In this case, it is useful to have a way to place the memmap on the
> memory being added, even if it means splitting the addition into
> memblock-sized chunks.
>
> Change add_memory_resource() to loop over memblock-sized chunks of
> memory if caller requested memmap_on_memory, and if other conditions for
> it are met. Teach try_remove_memory() to also expect that a memory
> range being removed might have been split up into memblock sized chunks,
> and to loop through those as needed.
>
> This does preclude being able to use PUD mappings in the direct map; a
> proposal to how this could be optimized in the future is laid out
> here[1].
>
> [1]: https://lore.kernel.org/linux-mm/b6753402-2de9-25b2-36e9-eacd49752b19@redhat.com/
>
> Cc: Andrew Morton <akpm@linux-foundation.org>
> Cc: David Hildenbrand <david@redhat.com>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Oscar Salvador <osalvador@suse.de>
> Cc: Dan Williams <dan.j.williams@intel.com>
> Cc: Dave Jiang <dave.jiang@intel.com>
> Cc: Dave Hansen <dave.hansen@linux.intel.com>
> Cc: Huang Ying <ying.huang@intel.com>
> Suggested-by: David Hildenbrand <david@redhat.com>
> Reviewed-by: Dan Williams <dan.j.williams@intel.com>
> Signed-off-by: Vishal Verma <vishal.l.verma@intel.com>
> ---
> mm/memory_hotplug.c | 214 ++++++++++++++++++++++++++++++++++++----------------
> 1 file changed, 148 insertions(+), 66 deletions(-)
>
> diff --git a/mm/memory_hotplug.c b/mm/memory_hotplug.c
> index 6be7de9efa55..83e5ec377aad 100644
> --- a/mm/memory_hotplug.c
> +++ b/mm/memory_hotplug.c
> @@ -1380,6 +1380,43 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)
> return arch_supports_memmap_on_memory(vmemmap_size);
> }
>
> +static int add_memory_create_devices(int nid, struct memory_group *group,
> + u64 start, u64 size, mhp_t mhp_flags)
> +{
> + struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) };
> + struct vmem_altmap mhp_altmap = {
> + .base_pfn = PHYS_PFN(start),
> + .end_pfn = PHYS_PFN(start + size - 1),
> + };
> + int ret;
> +
> + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY)) {
> + mhp_altmap.free = memory_block_memmap_on_memory_pages();
> + params.altmap = kmemdup(&mhp_altmap, sizeof(struct vmem_altmap),
> + GFP_KERNEL);
> + if (!params.altmap)
> + return -ENOMEM;
> + }
> +
> + /* call arch's memory hotadd */
> + ret = arch_add_memory(nid, start, size, ¶ms);
> + if (ret < 0)
> + goto error;
> +
> + /* create memory block devices after memory was added */
> + ret = create_memory_block_devices(start, size, params.altmap, group);
> + if (ret)
> + goto err_bdev;
> +
> + return 0;
> +
> +err_bdev:
> + arch_remove_memory(start, size, NULL);
> +error:
> + kfree(params.altmap);
> + return ret;
> +}
> +
> /*
> * NOTE: The caller must call lock_device_hotplug() to serialize hotplug
> * and online/offline operations (triggered e.g. by sysfs).
> @@ -1388,14 +1425,10 @@ static bool mhp_supports_memmap_on_memory(unsigned long size)
> */
> int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> {
> - struct mhp_params params = { .pgprot = pgprot_mhp(PAGE_KERNEL) };
> + unsigned long memblock_size = memory_block_size_bytes();
> enum memblock_flags memblock_flags = MEMBLOCK_NONE;
> - struct vmem_altmap mhp_altmap = {
> - .base_pfn = PHYS_PFN(res->start),
> - .end_pfn = PHYS_PFN(res->end),
> - };
> struct memory_group *group = NULL;
> - u64 start, size;
> + u64 start, size, cur_start;
> bool new_node = false;
> int ret;
>
> @@ -1436,28 +1469,21 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> /*
> * Self hosted memmap array
> */
> - if (mhp_flags & MHP_MEMMAP_ON_MEMORY) {
> - if (mhp_supports_memmap_on_memory(size)) {
> - mhp_altmap.free = memory_block_memmap_on_memory_pages();
> - params.altmap = kmemdup(&mhp_altmap,
> - sizeof(struct vmem_altmap),
> - GFP_KERNEL);
> - if (!params.altmap)
> + if ((mhp_flags & MHP_MEMMAP_ON_MEMORY) &&
> + mhp_supports_memmap_on_memory(memblock_size)) {
> + for (cur_start = start; cur_start < start + size;
> + cur_start += memblock_size) {
> + ret = add_memory_create_devices(nid, group, cur_start,
> + memblock_size,
> + mhp_flags);
Just like on the removal part, that function doesn't make any sense to
be called with altmap and a bigger range.
Maybe better also move that loop into a function called
"create_altmap_and_memory_blocks()" , to be the opposite of
"remove_memory_blocks_and_altmaps()".
Then you can keep the existing !altmap code here in the "else" case.
Again, similar to the removal code below.
> + if (ret)
> goto error;
> }
> - /* fallback to not using altmap */
> - }
> -
> - /* call arch's memory hotadd */
> - ret = arch_add_memory(nid, start, size, ¶ms);
> - if (ret < 0)
> - goto error_free;
> -
> - /* create memory block devices after memory was added */
> - ret = create_memory_block_devices(start, size, params.altmap, group);
> - if (ret) {
> - arch_remove_memory(start, size, NULL);
> - goto error_free;
> + } else {
> + ret = add_memory_create_devices(nid, group, start, size,
> + mhp_flags);
> + if (ret)
> + goto error;
> }
>
> if (new_node) {
> @@ -1494,8 +1520,6 @@ int __ref add_memory_resource(int nid, struct resource *res, mhp_t mhp_flags)
> walk_memory_blocks(start, size, NULL, online_memory_block);
>
> return ret;
> -error_free:
> - kfree(params.altmap);
> error:
> if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK))
> memblock_remove(start, size);
> @@ -2076,6 +2100,23 @@ static int test_has_altmap_cb(struct memory_block *mem, void *arg)
> return 0;
> }
[...]
> +
> +static int memblocks_have_altmaps(u64 start, u64 size)
> +{
> + struct memory_range_altmap_info altmap_info = {
> + .num_memblocks = 0,
> + .num_altmaps = 0
> + };
You can get the number of memblocks simply by "size /
memory_block_size_bytes()". So you can avoid the "struct" and just pass
an int.
> +
> + if (!mhp_memmap_on_memory())
> + return 0;
> +
> + walk_memory_blocks(start, size, &altmap_info,
> + count_memory_range_altmaps_cb);
> +
> + if (!altmap_info.num_altmaps)
> + return 0;
> +
> + if (altmap_info.num_memblocks != altmap_info.num_altmaps) {
> + WARN_ONCE(1, "Not all memblocks in range have altmaps");
> + return -EINVAL;
> + }
> +
> + return 1;
> +}
> +
> +static int __ref try_remove_memory(u64 start, u64 size)
> +{
> + int rc, nid = NUMA_NO_NODE;
>
> BUG_ON(check_hotplug_memory_range(start, size));
>
> @@ -2167,45 +2272,21 @@ static int __ref try_remove_memory(u64 start, u64 size)
> if (rc)
> return rc;
>
> - /*
> - * We only support removing memory added with MHP_MEMMAP_ON_MEMORY in
> - * the same granularity it was added - a single memory block.
> - */
> - if (mhp_memmap_on_memory()) {
> - rc = walk_memory_blocks(start, size, &mem, test_has_altmap_cb);
> - if (rc) {
> - if (size != memory_block_size_bytes()) {
> - pr_warn("Refuse to remove %#llx - %#llx,"
> - "wrong granularity\n",
> - start, start + size);
> - return -EINVAL;
> - }
> - altmap = mem->altmap;
> - /*
> - * Mark altmap NULL so that we can add a debug
> - * check on memblock free.
> - */
> - mem->altmap = NULL;
> - }
> - }
> -
> /* remove memmap entry */
> firmware_map_remove(start, start + size, "System RAM");
>
> - /*
> - * Memory block device removal under the device_hotplug_lock is
> - * a barrier against racing online attempts.
> - */
Maybe move that comment into the else branch and not into
remove_memory_blocks_and_altmaps
> - remove_memory_block_devices(start, size);
> -
> mem_hotplug_begin();
>
> - arch_remove_memory(start, size, altmap);
> -
> - /* Verify that all vmemmap pages have actually been freed. */
> - if (altmap) {
> - WARN(altmap->alloc, "Altmap not fully unmapped");
> - kfree(altmap);
> + rc = memblocks_have_altmaps(start, size);
Don't use the term memblocks here, to not confuse it with the memblock
allocator.
"memory blocks" or "memory block devices". it's complicated.
> + if (rc < 0) {
> + goto err;
> + } else if (rc == 0) {
> + /* no altmaps, do the removal directly */
> + remove_memory_block_devices(start, size);
> + arch_remove_memory(start, size, NULL);
> + } else {
> + /* all memblocks in the range have altmaps */
> + remove_memory_blocks_and_altmaps(start, size);
> }
>
> if (IS_ENABLED(CONFIG_ARCH_KEEP_MEMBLOCK)) {
> @@ -2218,8 +2299,9 @@ static int __ref try_remove_memory(u64 start, u64 size)
> if (nid != NUMA_NO_NODE)
> try_offline_node(nid);
>
> +err:
> mem_hotplug_done();
> - return 0;
> + return (rc < 0 ? rc : 0);
> }
>
> /**
>
--
Cheers,
David / dhildenb
next prev parent reply other threads:[~2023-10-17 14:49 UTC|newest]
Thread overview: 7+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-10-17 5:44 [PATCH v6 0/3] mm: use memmap_on_memory semantics for dax/kmem Vishal Verma
2023-10-17 5:44 ` [PATCH v6 1/3] mm/memory_hotplug: replace an open-coded kmemdup() in add_memory_resource() Vishal Verma
2023-10-17 14:39 ` David Hildenbrand
2023-10-17 5:44 ` [PATCH v6 2/3] mm/memory_hotplug: split memmap_on_memory requests across memblocks Vishal Verma
2023-10-17 6:33 ` Huang, Ying
2023-10-17 14:49 ` David Hildenbrand [this message]
2023-10-17 5:44 ` [PATCH v6 3/3] dax/kmem: allow kmem to add memory with memmap_on_memory Vishal Verma
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