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From: Chen Wandun <chenwandun@huawei.com>
To: Andrew Morton <akpm@linux-foundation.org>
Cc: <npiggin@gmail.com>, <linux-mm@kvack.org>,
	<linux-kernel@vger.kernel.org>, <edumazet@google.com>,
	<wangkefeng.wang@huawei.com>, <guohanjun@huawei.com>
Subject: Re: [PATCH] mm/vmalloc: fix numa spreading for large hash tables
Date: Thu, 14 Oct 2021 16:50:16 +0800	[thread overview]
Message-ID: <9d6f8c72-8bcb-39ce-baa8-00e42e5e97da@huawei.com> (raw)
In-Reply-To: <20210928153302.f87537b5faac8637c3c5eb53@linux-foundation.org>



在 2021/9/29 6:33, Andrew Morton 写道:
> On Tue, 28 Sep 2021 20:10:40 +0800 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>
> 
> This seems like it could cause significant performance regressions in
> some situations?
Yes,I indeed will cause some performance regressions, I will send a 
optimization patch based on this patch.
> 
> If "yes" then wouldn't a cc:stable be appropriate?  And some (perhaps
> handwavy) quantification of the slowdown would help people understand
> why we're recommending a backport.
> 
> If "no" then why the heck do we have that feature in there anyway ;)
> 
> .
> 

  reply	other threads:[~2021-10-14  8:50 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 [this message]
2021-10-13 21:46 ` Shakeel Butt
2021-10-14  8:59   ` Chen Wandun
2021-10-15  1:34     ` Nicholas Piggin
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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