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Date: Wed, 13 Oct 2021 19:30:32 -0700
From: Mike Kravetz <mike.kravetz@...cle.com>
To: Baolin Wang <baolin.wang@...ux.alibaba.com>,
akpm@...ux-foundation.org
Cc: mhocko@...nel.org, guro@...com, corbet@....net,
yaozhenguo1@...il.com, linux-mm@...ck.org,
linux-kernel@...r.kernel.org, linux-doc@...r.kernel.org
Subject: Re: [PATCH] hugetlb: Support node specified when using cma for
gigantic hugepages
On 10/13/21 7:23 PM, Baolin Wang wrote:
>
>
> On 2021/10/14 6:06, Mike Kravetz wrote:
>> On 10/9/21 10:24 PM, Baolin Wang wrote:
>>> Now the size of CMA area for gigantic hugepages runtime allocation is
>>> balanced for all online nodes, but we also want to specify the size of
>>> CMA per-node, or only one node in some cases, which are similar with
>>> commit 86acc55c3d32 ("hugetlbfs: extend the definition of hugepages
>>> parameter to support node allocation")[1].
>>>
>>> Thus this patch adds node format for 'hugetlb_cma' parameter to support
>>> specifying the size of CMA per-node. An example is as follows:
>>>
>>> hugetlb_cma=0:5G,2:5G
>>>
>>> which means allocating 5G size of CMA area on node 0 and node 2
>>> respectively.
>>>
>>> [1]
>>> https://lkml.kernel.org/r/20211005054729.86457-1-yaozhenguo1@gmail.com
>>>
>>> Signed-off-by: Baolin Wang <baolin.wang@...ux.alibaba.com>
>>> ---
>>> Documentation/admin-guide/kernel-parameters.txt | 6 +-
>>> mm/hugetlb.c | 79 +++++++++++++++++++++----
>>> 2 files changed, 73 insertions(+), 12 deletions(-)
>>>
>>> diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt
>>> index 3ad8e9d0..a147faa5 100644
>>> --- a/Documentation/admin-guide/kernel-parameters.txt
>>> +++ b/Documentation/admin-guide/kernel-parameters.txt
>>> @@ -1587,8 +1587,10 @@
>>> registers. Default set by CONFIG_HPET_MMAP_DEFAULT.
>>> hugetlb_cma= [HW,CMA] The size of a CMA area used for allocation
>>> - of gigantic hugepages.
>>> - Format: nn[KMGTPE]
>>> + of gigantic hugepages. Or using node format, the size
>>> + of a CMA area per node can be specified.
>>> + Format: nn[KMGTPE] or (node format)
>>> + <node>:nn[KMGTPE][,<node>:nn[KMGTPE]]
>>> Reserve a CMA area of given size and allocate gigantic
>>> hugepages using the CMA allocator. If enabled, the
>>> diff --git a/mm/hugetlb.c b/mm/hugetlb.c
>>> index 6d2f4c2..8b4e409 100644
>>> --- a/mm/hugetlb.c
>>> +++ b/mm/hugetlb.c
>>> @@ -50,6 +50,7 @@
>>> #ifdef CONFIG_CMA
>>> static struct cma *hugetlb_cma[MAX_NUMNODES];
>>> +static unsigned long hugetlb_cma_size_in_node[MAX_NUMNODES] __initdata;
>>> static bool hugetlb_cma_page(struct page *page, unsigned int order)
>>> {
>>> return cma_pages_valid(hugetlb_cma[page_to_nid(page)], page,
>>> @@ -62,6 +63,7 @@ static bool hugetlb_cma_page(struct page *page, unsigned int order)
>>> }
>>> #endif
>>> static unsigned long hugetlb_cma_size __initdata;
>>> +static nodemask_t hugetlb_cma_nodes_allowed = NODE_MASK_NONE;
>>> /*
>>> * Minimum page order among possible hugepage sizes, set to a proper value
>>> @@ -3497,9 +3499,15 @@ static ssize_t __nr_hugepages_store_common(bool obey_mempolicy,
>>> if (nid == NUMA_NO_NODE) {
>>> /*
>>> + * If we've specified the size of CMA area per node,
>>> + * should use it firstly.
>>> + */
>>> + if (hstate_is_gigantic(h) && !nodes_empty(hugetlb_cma_nodes_allowed))
>>> + n_mask = &hugetlb_cma_nodes_allowed;
>>> + /*
>>
>> IIUC, this changes the behavior for 'balanced' gigantic huge page pool
>> allocations if per-node hugetlb_cma is specified. It will now only
>> attempt to allocate gigantic pages on nodes where CMA was reserved.
>> Even if we run out of space on the node, it will not go to other nodes
>> as before. Is that correct?
>
> Right.
>
>>
>> I do not believe we want this change in behavior. IMO, if the user is
>> doing node specific CMA reservations, then the user should use the node
>> specific sysfs file for pool allocations on that node.
>
> Sounds more reasonable, will move 'hugetlb_cma_nodes_allowed' to the node specific allocation.
>
>>> * global hstate attribute
>>> */
>>> - if (!(obey_mempolicy &&
>>> + else if (!(obey_mempolicy &&
>>> init_nodemask_of_mempolicy(&nodes_allowed)))
>>> n_mask = &node_states[N_MEMORY];
>>> else
>>> @@ -6745,7 +6753,38 @@ void hugetlb_unshare_all_pmds(struct vm_area_struct *vma)
>>> static int __init cmdline_parse_hugetlb_cma(char *p)
>>> {
>>> - hugetlb_cma_size = memparse(p, &p);
>>> + int nid, count = 0;
>>> + unsigned long tmp;
>>> + char *s = p;
>>> +
>>> + while (*s) {
>>> + if (sscanf(s, "%lu%n", &tmp, &count) != 1)
>>> + break;
>>> +
>>> + if (s[count] == ':') {
>>> + nid = tmp;
>>> + if (nid < 0 || nid >= MAX_NUMNODES)
>>> + break;
>>
>> nid can only be compared to MAX_NUMNODES because this an early param
>> before numa is setup and we do not know exactly how many nodes there
>> are. Is this correct?
>
> Yes.
>
>>
>> Suppose one specifies an invaid node. For example, on my 2 node system
>> I use the option 'hugetlb_cma=2:2G'. This is not flagged as an error
>> during processing and 1G CMA is reserved on node 0 and 1G is reserved
>> on node 1. Is that by design, or just chance?
>
> Actually we won't allocate any CMA area in this case, since in hugetlb_cma_reserve(), we will only iterate the online nodes to try to allocate CMA area, and node 2 is not in the range of online nodes in this case.
>
But, since it can not do node specifric allocations it falls through to
the all nodes case? Here is what I see:
# numactl -H
available: 2 nodes (0-1)
node 0 cpus: 0 1
node 0 size: 8053 MB
node 0 free: 6543 MB
node 1 cpus: 2 3
node 1 size: 8150 MB
node 1 free: 4851 MB
node distances:
node 0 1
0: 10 20
1: 20 10
# reboot
# dmesg | grep -i huge
[ 0.000000] Command line: BOOT_IMAGE=/vmlinuz-5.15.0-rc4-mm1+ root=/dev/mapper/fedora_new--host-root ro rd.lvm.lv=fedora_new-host/root rd.lvm.lv=fedora_new-host/swap console=tty0 console=ttyS0,115200 audit=0 transparent_hugepage=always hugetlb_free_vmemmap=on hugetlb_cma=2:2G
[ 0.008345] hugetlb_cma: reserve 2048 MiB, up to 1024 MiB per node
[ 0.008349] hugetlb_cma: reserved 1024 MiB on node 0
[ 0.008352] hugetlb_cma: reserved 1024 MiB on node 1
[ 0.053682] Kernel command line: BOOT_IMAGE=/vmlinuz-5.15.0-rc4-mm1+ root=/dev/mapper/fedora_new--host-root ro rd.lvm.lv=fedora_new-host/root rd.lvm.lv=fedora_new-host/swap console=tty0 console=ttyS0,115200 audit=0 transparent_hugepage=always hugetlb_free_vmemmap=on hugetlb_cma=2:2G
[ 0.401648] HugeTLB: can free 4094 vmemmap pages for hugepages-1048576kB
[ 0.413681] HugeTLB: can free 6 vmemmap pages for hugepages-2048kB
[ 0.414590] HugeTLB registered 1.00 GiB page size, pre-allocated 0 pages
[ 0.415653] HugeTLB registered 2.00 MiB page size, pre-allocated 0 pages
--
Mike Kravetz
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