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Date: Thu, 14 Oct 2021 16:59:10 +0800
From: Chen Wandun <chenwandun@...wei.com>
To: Shakeel Butt <shakeelb@...gle.com>
CC: Andrew Morton <akpm@...ux-foundation.org>,
Nicholas Piggin <npiggin@...il.com>,
Linux MM <linux-mm@...ck.org>,
LKML <linux-kernel@...r.kernel.org>,
Eric Dumazet <edumazet@...gle.com>,
"Kefeng Wang" <wangkefeng.wang@...wei.com>, <guohanjun@...wei.com>
Subject: Re: [PATCH] mm/vmalloc: fix numa spreading for large hash tables
在 2021/10/14 5:46, Shakeel Butt 写道:
> On Tue, Sep 28, 2021 at 5:03 AM Chen Wandun <chenwandun@...wei.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@...gle.com>
>> Signed-off-by: Chen Wandun <chenwandun@...wei.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,
Wandun
>
>> - nr = alloc_pages_bulk_array_node(gfp, nid,
>> - nr_pages_request, pages + nr_allocated);
>> -
>> + if (nid == NUMA_NO_NODE) {
>> + for (i = 0; i < nr_pages_request; i++) {
>> + page = alloc_page(gfp);
>> + if (page)
>> + pages[nr_allocated + i] = page;
>> + else {
>> + nr = i;
>> + break;
>> + }
>> + }
>> + if (i >= nr_pages_request)
>> + nr = nr_pages_request;
>> + } else {
>> + nr = alloc_pages_bulk_array_node(gfp, nid,
>> + nr_pages_request,
>> + pages + nr_allocated);
>> + }
>> nr_allocated += nr;
>> cond_resched();
>>
>> @@ -2863,11 +2880,13 @@ vm_area_alloc_pages(gfp_t gfp, int nid,
>
> Put the following line under "else if (order)"
>
>> gfp |= __GFP_COMP;
>>
>> /* High-order pages or fallback path if "bulk" fails. */
>> - while (nr_allocated < nr_pages) {
>
> Keep the following declarations inside the while loop.
>
>> - struct page *page;
>> - int i;
>>
>> - page = alloc_pages_node(nid, gfp, order);
>> + page = NULL;
>> + while (nr_allocated < nr_pages) {
>> + if (nid == NUMA_NO_NODE)
>> + page = alloc_pages(gfp, order);
>> + else
>> + page = alloc_pages_node(nid, gfp, order);
>> if (unlikely(!page))
>> break;
>>
>> --
>> 2.25.1
>>
> .
>
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