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SubjectRe: [PATCH v4] hugetlbfs: Extend the definition of hugepages parameter to support node allocation
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Now, really CC'ing Mike, and sorry for misspelling your name

On 9/15/21 3:03 PM, Mike Kravetz wrote:
> On 9/15/21 6:11 AM, zhenguo yao wrote:
>> Andrew Morton <akpm@linux-foundation.org> 于2021年9月15日周三 上午11:50写道:
>>>
>>> On Thu, 9 Sep 2021 22:16:55 +0800 yaozhenguo <yaozhenguo1@gmail.com> wrote:
>>>
>>>> We can specify the number of hugepages to allocate at boot. But the
>>>> hugepages is balanced in all nodes at present. In some scenarios,
>>>> we only need hugepages in one node. For example: DPDK needs hugepages
>>>> which are in the same node as NIC. if DPDK needs four hugepages of 1G
>>>> size in node1 and system has 16 numa nodes. We must reserve 64 hugepages
>>>> in kernel cmdline. But, only four hugepages are used. The others should
>>>> be free after boot. If the system memory is low(for example: 64G), it will
>>>> be an impossible task. So, Extending hugepages parameter to support
>>>> specifying hugepages at a specific node.
>>>> For example add following parameter:
>>>>
>>>> hugepagesz=1G hugepages=0:1,1:3
>>>>
>>>> It will allocate 1 hugepage in node0 and 3 hugepages in node1.
>>>>
>>>> ...
>>>>
>>>> @@ -2842,10 +2843,75 @@ static void __init gather_bootmem_prealloc(void)
>>>> }
>>>> }
>>>>
>>>> +static void __init hugetlb_hstate_alloc_pages_onenode(struct hstate *h, int nid)
>>>> +{
>>>> + unsigned long i;
>>>> + char buf[32];
>>>> +
>>>> + for (i = 0; i < h->max_huge_pages_node[nid]; ++i) {
>>>> + if (hstate_is_gigantic(h)) {
>>>> + struct huge_bootmem_page *m;
>>>> + void *addr;
>>>> +
>>>> + addr = memblock_alloc_try_nid_raw(
>>>> + huge_page_size(h), huge_page_size(h),
>>>> + 0, MEMBLOCK_ALLOC_ACCESSIBLE, nid);
>>>> + if (!addr)
>>>> + break;
>>>> + m = addr;
>>>> + BUG_ON(!IS_ALIGNED(virt_to_phys(m), huge_page_size(h)));
>>>
>>> We try very hard to avoid adding BUG calls. Is there any way in which
>>> this code can emit a WARNing then permit the kernel to keep operating?
>>>
>> Maybe we can rewrite it as below:
>> if (WARN(!IS_ALIGNED(virt_to_phys(m),
>> huge_page_size(h)),
>> "HugeTLB: page addr:%p is not aligned\n", m))
>> break;
>> @Mike, Do you think it's OK?
>
> Sorry, I have not yet reviewed the latest version of this patch.
> Quick thought on this question.
>
> The required alignment passed to memblock_alloc_try_nid_raw() is
> huge_page_size(h). Therefore, we know the virtual address m is
> huge_page_size(h) aligned. The BUG is just checking to make sure
> the physical address associated with the virtual address is aligned
> the same. I really do not see how this could not be the case.
> In fact, the memblock allocator finds a physical address with the
> required alignment and then returns phys_to_virt(alloc).
> Someone please correct me if I am wrong. Otherwise, we can drop
> the BUG.
> Adding Mike Rapport on Cc:
>
> This allocation code and the associated BUG was copied from
> __alloc_bootmem_huge_page(). The BUG was added 12 years ago before
> the memblock allocator existed and we were using the bootmem allocator.
> If there is no need for a BUG in hugetlb_hstate_alloc_pages_onenode,
> there is no need for one in __alloc_bootmem_huge_page.
>


--
Mike Kravetz

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