linux-kernel - Re: [PATCH v5 4/5] mm/sparse: add new sparse_init_nid() and sparse

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Message-ID: <20180713120340.GA16552@techadventures.net>
Date:   Fri, 13 Jul 2018 14:03:40 +0200
From:   Oscar Salvador <osalvador@...hadventures.net>
To:     Pavel Tatashin <pasha.tatashin@...cle.com>
Cc:     steven.sistare@...cle.com, daniel.m.jordan@...cle.com,
        linux-kernel@...r.kernel.org, akpm@...ux-foundation.org,
        kirill.shutemov@...ux.intel.com, mhocko@...e.com,
        linux-mm@...ck.org, dan.j.williams@...el.com, jack@...e.cz,
        jglisse@...hat.com, jrdr.linux@...il.com, bhe@...hat.com,
        gregkh@...uxfoundation.org, vbabka@...e.cz,
        richard.weiyang@...il.com, dave.hansen@...el.com,
        rientjes@...gle.com, mingo@...nel.org, abdhalee@...ux.vnet.ibm.com,
        mpe@...erman.id.au
Subject: Re: [PATCH v5 4/5] mm/sparse: add new sparse_init_nid() and
 sparse_init()

On Thu, Jul 12, 2018 at 04:37:29PM -0400, Pavel Tatashin wrote:
> sparse_init() requires to temporary allocate two large buffers:
> usemap_map and map_map. Baoquan He has identified that these buffers are so
> large that Linux is not bootable on small memory machines, such as a kdump
> boot. The buffers are especially large when CONFIG_X86_5LEVEL is set, as
> they are scaled to the maximum physical memory size.
> 
> Baoquan provided a fix, which reduces these sizes of these buffers, but it
> is much better to get rid of them entirely.
> 
> Add a new way to initialize sparse memory: sparse_init_nid(), which only
> operates within one memory node, and thus allocates memory either in large
> contiguous block or allocates section by section. This eliminates the need
> for use of temporary buffers.
> 
> For simplified bisecting and review temporarly call sparse_init()
> new_sparse_init(), the new interface is going to be enabled as well as old
> code removed in the next patch.
> 
> Signed-off-by: Pavel Tatashin <pasha.tatashin@...cle.com>

Looks good to me, and it will make the code much shorter/easier.

Reviewed-by: Oscar Salvador <osalvador@...e.de>

Thanks
-- 
Oscar Salvador
SUSE L3