Re: [PATCH] mm/vmalloc: fix numa spreading for large hash tables

[Chen Wandun]

在 2021/10/14 18:01, Uladzislau Rezki 写道:
> On Tue, Sep 28, 2021 at 08:10:40PM +0800, Chen Wandun wrote:
> > Eric Dumazet reported a strange numa spreading info in [1], and found
> > commit 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings") introduced
> > this issue [2].
> >
> > Dig into the difference before and after this patch, page allocation has
> > some difference:
> >
> > before:
> > alloc_large_system_hash
> >      __vmalloc
> >          __vmalloc_node(..., NUMA_NO_NODE, ...)
> >              __vmalloc_node_range
> >                  __vmalloc_area_node
> >                      alloc_page /* because NUMA_NO_NODE, so choose alloc_page branch */
> >                          alloc_pages_current
> >                              alloc_page_interleave /* can be proved by print policy mode */
> >
> > after:
> > alloc_large_system_hash
> >      __vmalloc
> >          __vmalloc_node(..., NUMA_NO_NODE, ...)
> >              __vmalloc_node_range
> >                  __vmalloc_area_node
> >                      alloc_pages_node /* choose nid by nuam_mem_id() */
> >                          __alloc_pages_node(nid, ....)
> >
> > So after commit 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings"),
> > it will allocate memory in current node instead of interleaving allocate
> > memory.
> >
> > [1]
> > https://lore.kernel.org/linux-mm/CANn89iL6AAyWhfxdHO+jaT075iOa3XcYn9k6JJc7JR2XYn6k_Q@xxxxxxxxxxxxxx/
> >
> > [2]
> > https://lore.kernel.org/linux-mm/CANn89iLofTR=AK-QOZY87RdUZENCZUT4O6a0hvhu3_EwRMerOg@xxxxxxxxxxxxxx/
> >
> > Fixes: 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings")
> > Reported-by: Eric Dumazet <edumazet@xxxxxxxxxx>
> > Signed-off-by: Chen Wandun <chenwandun@xxxxxxxxxx>
> > ---
> >   mm/vmalloc.c | 33 ++++++++++++++++++++++++++-------
> >   1 file changed, 26 insertions(+), 7 deletions(-)
> >
> > diff --git a/mm/vmalloc.c b/mm/vmalloc.c
> > index f884706c5280..48e717626e94 100644
> > --- a/mm/vmalloc.c
> > +++ b/mm/vmalloc.c
> > @@ -2823,6 +2823,8 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> >   		unsigned int order, unsigned int nr_pages, struct page **pages)
> >   {
> >   	unsigned int nr_allocated = 0;
> > +	struct page *page;
> > +	int i;
> >   
> >   	/*
> >   	 * For order-0 pages we make use of bulk allocator, if
> > @@ -2833,6 +2835,7 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> >   	if (!order) {
> >   		while (nr_allocated < nr_pages) {
> >   			unsigned int nr, nr_pages_request;
> > +			page = NULL;
> >   
> >   			/*
> >   			 * A maximum allowed request is hard-coded and is 100
> > @@ -2842,9 +2845,23 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
> >   			 */
> >   			nr_pages_request = min(100U, nr_pages - nr_allocated);
> >   
> > -			nr = alloc_pages_bulk_array_node(gfp, nid,
> > -				nr_pages_request, pages + nr_allocated);
> > -
> > +			if (nid == NUMA_NO_NODE) {
> <snip>
> void *vmalloc(unsigned long size)
> {
> 	return __vmalloc_node(size, 1, GFP_KERNEL, NUMA_NO_NODE,
> 		__builtin_return_address(0));
> }
> EXPORT_SYMBOL(vmalloc);
> <snip>
>
> vmalloc() uses NUMA_NO_NODE, so all vmalloc calls will be reverted to a single
> page allocator for NUMA and non-NUMA systems. Is it intentional to bypass the
> optimized bulk allocator for non-NUMA systems?
I sent a patch, it will help to solve this.

[PATCH] mm/vmalloc: introduce alloc_pages_bulk_array_mempolicy to 
accelerate memory allocation

Thanks,
Wandun

> Thanks!
>
> --
> Vlad Rezki
> .