From: Dave Hansen <dave.hansen@linux.intel.com>
To: "Kirill A. Shutemov" <kirill@shutemov.name>, Baoquan He <bhe@redhat.com>
Cc: linux-kernel@vger.kernel.org, linux-mm@kvack.org,
akpm@linux-foundation.org, kirill.shutemov@linux.intel.com,
mhocko@suse.com, tglx@linutronix.de, douly.fnst@cn.fujitsu.com
Subject: Re: [PATCH 2/2] mm/sparse.c: Add nr_present_sections to change the mem_map allocation
Date: Thu, 1 Feb 2018 05:49:50 -0800 [thread overview]
Message-ID: <6def8374-2de2-a30c-69ff-2a49fb57dc9a@linux.intel.com> (raw)
In-Reply-To: <20180201101641.icoxv2sp6ckrjfxd@node.shutemov.name>
On 02/01/2018 02:16 AM, Kirill A. Shutemov wrote:
> On Thu, Feb 01, 2018 at 03:19:56PM +0800, Baoquan He wrote:
>> In sparse_init(), we allocate usemap_map and map_map which are pointer
>> array with the size of NR_MEM_SECTIONS. The memory consumption can be
>> ignorable in 4-level paging mode. While in 5-level paging, this costs
>> much memory, 512M. Kdump kernel even can't boot up with a normal
>> 'crashkernel=' setting.
>>
>> Here add a new variable to record the number of present sections. Let's
>> allocate the usemap_map and map_map with the size of nr_present_sections.
>> We only need to make sure that for the ith present section, usemap_map[i]
>> and map_map[i] store its usemap and mem_map separately.
>>
>> This change can save much memory on most of systems. Anytime, we should
>> avoid to define array or allocate memory with the size of NR_MEM_SECTIONS.
> That's very desirable outcome. But I don't know much about sparsemem.
... with the downside being that we can no longer hot-add memory that
was not part of the original, present sections.
Is that OK?
next prev parent reply other threads:[~2018-02-01 13:49 UTC|newest]
Thread overview: 10+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-01 7:19 [PATCH 0/2] Optimize the code of mem_map allocation in Baoquan He
2018-02-01 7:19 ` [PATCH 1/2] mm/sparsemem: Defer the ms->section_mem_map clearing a little later Baoquan He
2018-02-01 14:15 ` Dave Hansen
2018-02-01 14:38 ` Baoquan He
2018-02-01 7:19 ` [PATCH 2/2] mm/sparse.c: Add nr_present_sections to change the mem_map allocation Baoquan He
2018-02-01 10:16 ` Kirill A. Shutemov
2018-02-01 13:49 ` Dave Hansen [this message]
2018-02-01 14:19 ` Baoquan He
2018-02-01 14:23 ` Dave Hansen
2018-02-01 14:33 ` Baoquan He
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