From: Nicholas Piggin <npiggin@gmail.com>
To: Chen Wandun <chenwandun@huawei.com>, Shakeel Butt <shakeelb@google.com>
Cc: "Andrew Morton" <akpm@linux-foundation.org>,
"Eric Dumazet" <edumazet@google.com>,
guohanjun@huawei.com, LKML <linux-kernel@vger.kernel.org>,
"Linux MM" <linux-mm@kvack.org>,
"Kefeng\
Wang" <wangkefeng.wang@huawei.com>
Subject: Re: [PATCH] mm/vmalloc: fix numa spreading for large hash tables
Date: Fri, 15 Oct 2021 11:34:08 +1000 [thread overview]
Message-ID: <1634261360.fed2opbgxw.astroid@bobo.none> (raw)
In-Reply-To: <8fc5e1ae-a356-6225-2e50-cf0e5ee26208@huawei.com>
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@huawei.com> 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@mail.gmail.com/
>>>
>>> [2]
>>> https://lore.kernel.org/linux-mm/CANn89iLofTR=AK-QOZY87RdUZENCZUT4O6a0hvhu3_EwRMerOg@mail.gmail.com/
>>>
>>> Fixes: 121e6f3258fe ("mm/vmalloc: hugepage vmalloc mappings")
>>> Reported-by: Eric Dumazet <edumazet@google.com>
>>> Signed-off-by: Chen Wandun <chenwandun@huawei.com>
>>> ---
>>> 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?
diff --git a/mm/vmalloc.c b/mm/vmalloc.c
index d77830ff604c..75ee9679f521 100644
--- a/mm/vmalloc.c
+++ b/mm/vmalloc.c
@@ -2860,7 +2860,10 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
struct page *page;
int i;
- page = alloc_pages_node(nid, gfp, order);
+ if (nid == NUMA_NO_NODE)
+ page = alloc_pages(gfp, order);
+ else
+ page = alloc_pages_node(nid, gfp, order);
if (unlikely(!page))
break;
Thanks,
Nick
next prev parent reply other threads:[~2021-10-15 1:34 UTC|newest]
Thread overview: 16+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-09-28 12:10 [PATCH] mm/vmalloc: fix numa spreading for large hash tables Chen Wandun
2021-09-28 22:33 ` Andrew Morton
2021-10-14 8:50 ` Chen Wandun
2021-10-13 21:46 ` Shakeel Butt
2021-10-14 8:59 ` Chen Wandun
2021-10-15 1:34 ` Nicholas Piggin [this message]
2021-10-15 2:31 ` Chen Wandun
2021-10-15 7:11 ` Nicholas Piggin
2021-10-15 11:51 ` Eric Dumazet
2021-10-18 8:45 ` Chen Wandun
2021-10-16 16:46 ` Uladzislau Rezki
2021-10-14 9:29 ` [PATCH] mm/vmalloc: introduce alloc_pages_bulk_array_mempolicy to accelerate memory allocation Chen Wandun
2021-10-15 21:13 ` Andrew Morton
2021-10-16 16:27 ` Uladzislau Rezki
2021-10-14 10:01 ` [PATCH] mm/vmalloc: fix numa spreading for large hash tables Uladzislau Rezki
2021-10-15 2:20 ` Chen Wandun
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