Re: [PATCH v7] hugetlbfs: Extend the definition of hugepages parameter to support node allocation

Mike Rapoport
2021-09-29T22:27:22Z

On Wed, Sep 29, 2021 at 12:24:06PM -0700, Nathan Chancellor wrote:
> On Mon, Sep 27, 2021 at 06:41:49PM +0800, Zhenguo Yao 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.
> >
> > Signed-off-by: Zhenguo Yao <yaozhenguo1@gmail.com>
>
> <snip>
>
> > diff --git a/mm/hugetlb.c b/mm/hugetlb.c
> > index 95dc7b83381f..ca00676a1bdd 100644
> > --- a/mm/hugetlb.c
> > +++ b/mm/hugetlb.c
> > @@ -66,6 +66,7 @@ static struct hstate * __initdata parsed_hstate;
> > static unsigned long __initdata default_hstate_max_huge_pages;
> > static bool __initdata parsed_valid_hugepagesz = true;
> > static bool __initdata parsed_default_hugepagesz;
> > +static unsigned int default_hugepages_in_node[MAX_NUMNODES] __initdata;
> >
> > /*
> > * Protects updates to hugepage_freelists, hugepage_activelist, nr_huge_pages,
> > @@ -2868,33 +2869,41 @@ struct page *alloc_huge_page(struct vm_area_struct *vma,
> > return ERR_PTR(-ENOSPC);
> > }
> >
> > -int alloc_bootmem_huge_page(struct hstate *h)
> > +int alloc_bootmem_huge_page(struct hstate *h, int nid)
> > __attribute__ ((weak, alias("__alloc_bootmem_huge_page")));
> > -int __alloc_bootmem_huge_page(struct hstate *h)
> > +int __alloc_bootmem_huge_page(struct hstate *h, int nid)
> > {
> > struct huge_bootmem_page *m;
> > int nr_nodes, node;
> >
> > + if (nid >= nr_online_nodes)
> > + return 0;
> > + /* do node specific alloc */
> > + if (nid != NUMA_NO_NODE) {
> > + m = memblock_alloc_try_nid_raw(huge_page_size(h), huge_page_size(h),
> > + 0, MEMBLOCK_ALLOC_ACCESSIBLE, nid);
> > + if (m)
> > + goto found;
> > + else
> > + return 0;
> > + }
> > + /* do all node balanced alloc */
> > for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
> > - void *addr;
> > -
> > - addr = memblock_alloc_try_nid_raw(
> > + m = memblock_alloc_try_nid_raw(
> > huge_page_size(h), huge_page_size(h),
> > 0, MEMBLOCK_ALLOC_ACCESSIBLE, node);
> > - if (addr) {
> > - /*
> > - * Use the beginning of the huge page to store the
> > - * huge_bootmem_page struct (until gather_bootmem
> > - * puts them into the mem_map).
> > - */
> > - m = addr;
> > + /*
> > + * Use the beginning of the huge page to store the
> > + * huge_bootmem_page struct (until gather_bootmem
> > + * puts them into the mem_map).
> > + */
> > + if (m)
> > goto found;
> > - }
> > + else
> > + return 0;
> > }
> > - return 0;
> >
> > found:
> > - BUG_ON(!IS_ALIGNED(virt_to_phys(m), huge_page_size(h)));
> > /* Put them into a private list first because mem_map is not up yet */
> > INIT_LIST_HEAD(&m->list);
> > list_add(&m->list, &huge_boot_pages);
>
> This hunk causes a clang warning now:
>
> mm/hugetlb.c:2957:33: error: variable 'm' is used uninitialized whenever '&&' condition is false [-Werror,-Wsometimes-uninitialized]
> for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
> ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> mm/hugetlb.c:1254:3: note: expanded from macro 'for_each_node_mask_to_alloc'
> nr_nodes > 0 && \
> ^~~~~~~~~~~~
> mm/hugetlb.c:2974:18: note: uninitialized use occurs here
> INIT_LIST_HEAD(&m->list);
> ^
> mm/hugetlb.c:2957:33: note: remove the '&&' if its condition is always true
> for_each_node_mask_to_alloc(h, nr_nodes, node, &node_states[N_MEMORY]) {
> ^
> mm/hugetlb.c:2942:29: note: initialize the variable 'm' to silence this warning
> struct huge_bootmem_page *m;
> ^
> = NULL
> 1 error generated.
>
> I am not sure if it is possible for nr_nodes to be 0 right out of the
> gate so might be a false positive?

With nr_nodes == 0 there will be no memory in the system :)

--
Sincerely yours,
Mike.