linux-kernel - Re: [RFC 09/11] khugepaged: add mTHP support

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Message-ID: <ba1eb826-a610-4082-9a27-d3357d26feec@arm.com>
Date: Fri, 10 Jan 2025 19:06:55 +0530
From: Dev Jain <dev.jain@....com>
To: Nico Pache <npache@...hat.com>, linux-kernel@...r.kernel.org,
 linux-mm@...ck.org
Cc: ryan.roberts@....com, anshuman.khandual@....com, catalin.marinas@....com,
 cl@...two.org, vbabka@...e.cz, mhocko@...e.com, apopple@...dia.com,
 dave.hansen@...ux.intel.com, will@...nel.org, baohua@...nel.org,
 jack@...e.cz, srivatsa@...il.mit.edu, haowenchao22@...il.com,
 hughd@...gle.com, aneesh.kumar@...nel.org, yang@...amperecomputing.com,
 peterx@...hat.com, ioworker0@...il.com, wangkefeng.wang@...wei.com,
 ziy@...dia.com, jglisse@...gle.com, surenb@...gle.com,
 vishal.moola@...il.com, zokeefe@...gle.com, zhengqi.arch@...edance.com,
 jhubbard@...dia.com, 21cnbao@...il.com, willy@...radead.org,
 kirill.shutemov@...ux.intel.com, david@...hat.com, aarcange@...hat.com,
 raquini@...hat.com, sunnanyong@...wei.com, usamaarif642@...il.com,
 audra@...hat.com, akpm@...ux-foundation.org
Subject: Re: [RFC 09/11] khugepaged: add mTHP support



On 09/01/25 5:01 am, Nico Pache wrote:
> Introduce the ability for khugepaged to collapse to different mTHP sizes.
> While scanning a PMD range for potential hugepage collapse, track pages
> in MIN_MTHP_ORDER chunks. Each bit represents a fully utilized region of
> order MIN_MTHP_ORDER ptes.
> 
> With this bitmap we can determine which mTHP sizes would be the most
> efficient to collapse to if the PMD collapse is not suitible.
> 
> Signed-off-by: Nico Pache <npache@...hat.com>

For the actual bitmap optimization: give me some time, I'll get back to you.