linux-kernel - Re: [RESEND PATCH v7 00/10] Small-sized THP for anonymous memory

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Message-ID: <ZV97RO3i02+NmwD2@casper.infradead.org>
Date:   Thu, 23 Nov 2023 16:18:12 +0000
From:   Matthew Wilcox <willy@...radead.org>
To:     David Hildenbrand <david@...hat.com>
Cc:     Ryan Roberts <ryan.roberts@....com>,
        Andrew Morton <akpm@...ux-foundation.org>,
        Yin Fengwei <fengwei.yin@...el.com>,
        Yu Zhao <yuzhao@...gle.com>,
        Catalin Marinas <catalin.marinas@....com>,
        Anshuman Khandual <anshuman.khandual@....com>,
        Yang Shi <shy828301@...il.com>,
        "Huang, Ying" <ying.huang@...el.com>, Zi Yan <ziy@...dia.com>,
        Luis Chamberlain <mcgrof@...nel.org>,
        Itaru Kitayama <itaru.kitayama@...il.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        John Hubbard <jhubbard@...dia.com>,
        David Rientjes <rientjes@...gle.com>,
        Vlastimil Babka <vbabka@...e.cz>,
        Hugh Dickins <hughd@...gle.com>,
        Kefeng Wang <wangkefeng.wang@...wei.com>, linux-mm@...ck.org,
        linux-arm-kernel@...ts.infradead.org, linux-kernel@...r.kernel.org
Subject: Re: [RESEND PATCH v7 00/10] Small-sized THP for anonymous memory

On Thu, Nov 23, 2023 at 05:05:37PM +0100, David Hildenbrand wrote:
> On 23.11.23 16:59, Matthew Wilcox wrote:
> > On Wed, Nov 22, 2023 at 04:29:40PM +0000, Ryan Roberts wrote:
> > > Note: I'm resending this at Andrew's suggestion due to having originally sent
> > > it during LPC. I'm hoping its in a position where the feedback is minor enough
> > > that I can rework in time for v6.8, but so far haven't had any.
> > > 
> > > Hi All,
> > > 
> > > This is v7 of a series to implement small-sized THP for anonymous memory
> > > (previously called "large anonymous folios"). The objective of this is to
> > 
> > I'm still against small-sized THP.  We've now got people asking whether
> > the THP counters should be updated when dealing with large folios that
> > are smaller than PMD sized.  It's sowing confusion, and we should go
> > back to large anon folios as a name.
> > 
> 
> I disagree.
> 
> https://lore.kernel.org/all/65dbdf2a-9281-a3c3-b7e3-a79c5b60b357@redhat.com/

And yet:
https://lore.kernel.org/linux-mm/20231106193315.GB3661273@cmpxchg.org/

"This is a small THP so we don't account it as a THP, we only account
normal THPs as THPs" is a bizarre position to take.

Not to mention that saying a foo is a small huge baz is just bizarre.
Am I a small giant?  Or just a large human?