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Subject: Re: [PATCH 0/5] Parallel hugepage migration optimization
To: Zi Yan <zi.yan@sent.com>, linux-kernel@vger.kernel.org,
        linux-mm@kvack.org
References: <20161122162530.2370-1-zi.yan@sent.com>
Cc: akpm@linux-foundation.org, minchan@kernel.org, vbabka@suse.cz,
        mgorman@techsingularity.net, kirill.shutemov@linux.intel.com,
        n-horiguchi@ah.jp.nec.com, khandual@linux.vnet.ibm.com,
        Zi Yan <zi.yan@cs.rutgers.edu>
From: Balbir Singh <bsingharora@gmail.com>
Message-ID: <9cf7f4c6-6dde-9dbb-cf93-7874437a442d@gmail.com>
Date: Fri, 25 Nov 2016 10:59:20 +1100
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On 23/11/16 03:25, Zi Yan wrote:
> From: Zi Yan <zi.yan@cs.rutgers.edu>
> 
> Hi all,
> 
> This patchset boosts the hugepage migration throughput and helps THP migration
> which is added by Naoya's patches: https://lwn.net/Articles/705879/.
> 
> Motivation
> ===============================
> 
> In x86, 4KB page migrations are underutilizing the memory bandwidth compared
> to 2MB THP migrations. I did some page migration benchmarking on a two-socket
> Intel Xeon E5-2640v3 box, which has 23.4GB/s bandwidth, and discover
> there are big throughput gap, ~3x, between 4KB and 2MB page migrations.
> 
> Here are the throughput numbers for different page sizes and page numbers:
>         | 512 4KB pages | 1 2MB THP  |  1 4KB page
> x86_64  |  0.98GB/s     |  2.97GB/s  |   0.06GB/s
> 
> As Linux currently use single-threaded page migration, the throughput is still
> much lower than the hardware bandwidth, 2.97GB/s vs 23.4GB/s. So I parallelize
> the copy_page() part of THP migration with workqueue and achieve 2.8x throughput.
> 
> Here are the throughput numbers of 2MB page migration:
>            |  single-threaded   | 8-thread
> x86_64 2MB |    2.97GB/s        | 8.58GB/s
> 

Whats the impact on CPU utilization? Is there a huge impact?

Balbir Singh.