On Fri, Oct 15, 2021 at 05:11:25PM +1000, Nicholas Piggin wrote:
> Excerpts from Chen Wandun's message of October 15, 2021 12:31 pm:
> >
> >
> > 在 2021/10/15 9:34, Nicholas Piggin 写道:
> >> Excerpts from Chen Wandun's message of October 14, 2021 6:59 pm:
> >>>
> >>>
> >>> 在 2021/10/14 5:46, Shakeel Butt 写道:
> >>>> On Tue, Sep 28, 2021 at 5:03 AM Chen Wandun <chenwandun@xxxxxxxxxx> 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) {
> >>>>
> >>>> Can you please replace the above with if (!order && nid != NUMA_NO_NODE)?
> >>>>
> >>>>> 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);
> >>>>>
> >>>>
> >>>> Undo the following change in this if block.
> >>>
> >>> Yes, It seem like more simpler as you suggested, But it still have
> >>> performance regression, I plan to change the following to consider
> >>> both mempolcy and alloc_pages_bulk.
> >>
> >> Thanks for finding and debugging this. These APIs are a maze of twisty
> >> little passages, all alike so I could be as confused as I was when I
> >> wrote that patch, but doesn't a minimal fix look something like this?
> >
> > Yes, I sent a patch，it looks like as you show, besides it also
> > contains some performance optimization.
> >
> > [PATCH] mm/vmalloc: introduce alloc_pages_bulk_array_mempolicy to
> > accelerate memory allocation
>
> Okay. It would be better to do it as two patches. First the minimal fix
> so it can be backported easily and have the Fixes: tag pointed at my
> commit. Then the performance optimization.
>
It is not only your commit. It also fixes my one :)
<snip>
commit 5c1f4e690eecc795b2e4d4408e87302040fceca4
Author: Uladzislau Rezki (Sony) <urezki@xxxxxxxxx>
Date: Mon Jun 28 19:40:14 2021 -0700
mm/vmalloc: switch to bulk allocator in __vmalloc_area_node()
<snip>
I agree there should be two separate patches which fix NUMA balancing
issue, tagged with "Fixes" flag. One is located here:
https://lkml.org/lkml/2021/10/15/1172
second one should be that fixes a second place where "big" pages are
allocated, basically your patch.
--
Vlad Rezki
