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Date: Mon, 20 Mar 2017 14:32:27 -0700 (PDT)
From: David Rientjes <rientjes@google.com>
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To: "Huang, Ying" <ying.huang@intel.com>
cc: Andrew Morton <akpm@linux-foundation.org>,
        Andi Kleen <ak@linux.intel.com>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        Shaohua Li <shli@kernel.org>, Rik van Riel <riel@redhat.com>,
        Tim Chen <tim.c.chen@linux.intel.com>, Michal Hocko <mhocko@suse.com>,
        Mel Gorman <mgorman@techsingularity.net>,
        Aaron Lu <aaron.lu@intel.com>,
        Gerald Schaefer <gerald.schaefer@de.ibm.com>,
        "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>,
        Hugh Dickins <hughd@google.com>, Ingo Molnar <mingo@kernel.org>,
        Vegard Nossum <vegard.nossum@oracle.com>, linux-mm@kvack.org,
        linux-kernel@vger.kernel.org
Subject: Re: [PATCH -v2 1/2] mm, swap: Use kvzalloc to allocate some swap
 data structure
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On Mon, 20 Mar 2017, Huang, Ying wrote:

> From: Huang Ying <ying.huang@intel.com>
> 
> Now vzalloc() is used in swap code to allocate various data
> structures, such as swap cache, swap slots cache, cluster info, etc.
> Because the size may be too large on some system, so that normal
> kzalloc() may fail.  But using kzalloc() has some advantages, for
> example, less memory fragmentation, less TLB pressure, etc.  So change
> the data structure allocation in swap code to use kvzalloc() which
> will try kzalloc() firstly, and fallback to vzalloc() if kzalloc()
> failed.
> 

As questioned in -v1 of this patch, what is the benefit of directly 
compacting and reclaiming memory for high-order pages by first preferring 
kmalloc() if this does not require contiguous memory?