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

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Date:   Fri, 15 Oct 2021 10:20:48 +0800
From:   Chen Wandun <chenwandun@...wei.com>
To:     Uladzislau Rezki <urezki@...il.com>
CC:     <akpm@...ux-foundation.org>, <npiggin@...il.com>,
        <linux-mm@...ck.org>, <linux-kernel@...r.kernel.org>,
        <edumazet@...gle.com>, <wangkefeng.wang@...wei.com>,
        <guohanjun@...wei.com>
Subject: Re: [PATCH] mm/vmalloc: fix numa spreading for large hash tables



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@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) {
>>   		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
> .
>