linux-kernel - Re: [PATCH] mm: thp: don't have to lock page anymore when splitting PMD

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Date:   Mon, 7 Mar 2022 19:12:00 -0800
From:   Yang Shi <shy828301@...il.com>
To:     Hugh Dickins <hughd@...gle.com>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        David Hildenbrand <david@...hat.com>,
        Andrea Arcangeli <aarcange@...hat.com>,
        "Kirill A. Shutemov" <kirill.shutemov@...ux.intel.com>,
        Linux Kernel Mailing List <linux-kernel@...r.kernel.org>,
        Linux MM <linux-mm@...ck.org>,
        Matthew Wilcox <willy@...radead.org>,
        Naresh Kamboju <naresh.kamboju@...aro.org>
Subject: Re: [PATCH] mm: thp: don't have to lock page anymore when splitting PMD

On Mon, Mar 7, 2022 at 6:36 PM Hugh Dickins <hughd@...gle.com> wrote:
>
> On Mon, 7 Mar 2022, Andrew Morton wrote:
> >
> > OK, looks sane.  Can someone please test all this?
>
> Only the briefest of testing, but
>
> mmotm 2022-03-06-20-33
> minus mm-thp-dont-have-to-lock-page-anymore-when-splitting-pmd.patch
> plus mm-huge_memory-remove-stale-locking-logic-from-__split_huge_pmd.patch
> plus mm-huge_memory-remove-stale-locking-logic-from-__split_huge_pmd-fix.patch
>
> is infinitely better than mmotm 2022-03-06-20-33.
>
> I could just about reach a login on yesterday's mmotm, but graphics no.
> Couldn't spend time to investigate, but Naresh's mail today that LTP
> thp04 timeouted (hey, I'm English, we say timed out!) inspired me to
> try booting with transparent_hugepage=never on cmdline, and that worked.

I think it was because of
mm-thp-dont-have-to-lock-page-anymore-when-splitting-pmd.patch. It was
buggy (missed pmd_trans_huge(*pmd) check) and was dropped by Andrew.

>
> Again, no time to investigate, but the combination above has booted
> and is running load, including transparent hugepages.  And before
> setting that load going, I did try LTP thp04, which passed.
>
> (There is an unrelated console printk lockdep spew, and am I the only
> one to see these mm/workingset.c:567 shadow_lru_isolate warnings that
> started up a week or three ago?)
>
> Must dash,
> Hugh