linux-kernel - Re: [PATCH v11 00/15] khugepaged: mTHP support

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [thread-next>] [day] [month] [year] [list]

Message-ID: <92352257-5be4-4aaa-b97f-c4e879ac6959@lucifer.local>
Date: Mon, 15 Sep 2025 11:48:46 +0100
From: Lorenzo Stoakes <lorenzo.stoakes@...cle.com>
To: David Hildenbrand <david@...hat.com>
Cc: Kiryl Shutsemau <kas@...nel.org>, Nico Pache <npache@...hat.com>,
        linux-mm@...ck.org, linux-doc@...r.kernel.org,
        linux-kernel@...r.kernel.org, linux-trace-kernel@...r.kernel.org,
        ziy@...dia.com, baolin.wang@...ux.alibaba.com, Liam.Howlett@...cle.com,
        ryan.roberts@....com, dev.jain@....com, corbet@....net,
        rostedt@...dmis.org, mhiramat@...nel.org,
        mathieu.desnoyers@...icios.com, akpm@...ux-foundation.org,
        baohua@...nel.org, willy@...radead.org, peterx@...hat.com,
        wangkefeng.wang@...wei.com, usamaarif642@...il.com,
        sunnanyong@...wei.com, vishal.moola@...il.com,
        thomas.hellstrom@...ux.intel.com, yang@...amperecomputing.com,
        aarcange@...hat.com, raquini@...hat.com, anshuman.khandual@....com,
        catalin.marinas@....com, tiwai@...e.de, will@...nel.org,
        dave.hansen@...ux.intel.com, jack@...e.cz, cl@...two.org,
        jglisse@...gle.com, surenb@...gle.com, zokeefe@...gle.com,
        hannes@...xchg.org, rientjes@...gle.com, mhocko@...e.com,
        rdunlap@...radead.org, hughd@...gle.com, richard.weiyang@...il.com,
        lance.yang@...ux.dev, vbabka@...e.cz, rppt@...nel.org,
        jannh@...gle.com, pfalcato@...e.de
Subject: Re: [PATCH v11 00/15] khugepaged: mTHP support

On Mon, Sep 15, 2025 at 12:44:34PM +0200, David Hildenbrand wrote:
> > > > Mapping that to actual THP sizes (#pages in a thp) on an arch will be easy.
> > >
> > > And at different mTHP levels too right?
> > >
> >
> > Another point here, since we have to keep:
> >
> > /sys/kernel/mm/transparent_hugepage/khugepaged/max_ptes_none
> >
> > Around, and users will try to set values there, presumably we will now add:
> >
> > /sys/kernel/mm/transparent_hugepage/khugepaged/eagerness
> >
> > How will we map <-> the two tunables?
>
> Well, the easy case if someone updates eagerness, then we simply et it to
> whatever magic value we compute and document.
>
> The other direction is more problematic, likely we'll simply warn and do
> something reasonable (map it to whatever eagerness scale is closest or
> simply indicate it as "-1" -- user intervened or sth like that)

I don't love the idea of a -1 situation, as that's going to create some
confusion.

I'd really rather we just say out and out 'the kernel decides this based on
eagerness'.

So either warn or have some method to reverse-engineer what the closest value
might be.

Or perhaps just accept 0/511 there and map to eagerness min/max + if non-0/511
warn?

>
> --
> Cheers
>
> David / dhildenb
>

Cheers, Lorenzo