linux-kernel - Re: [PATCH] mm: split thp synchronously on MADV

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Message-ID: <CALvZod7xTfg5aeQC7-EaOZJ47Twb8CkoS6u4C=8+y+AX-NREVw@mail.gmail.com>
Date:   Tue, 23 Nov 2021 09:24:36 -0800
From:   Shakeel Butt <shakeelb@...gle.com>
To:     David Hildenbrand <david@...hat.com>
Cc:     "Kirill A . Shutemov" <kirill.shutemov@...ux.intel.com>,
        Yang Shi <shy828301@...il.com>, Zi Yan <ziy@...dia.com>,
        Matthew Wilcox <willy@...radead.org>,
        Andrew Morton <akpm@...ux-foundation.org>, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] mm: split thp synchronously on MADV_DONTNEED

On Tue, Nov 23, 2021 at 9:20 AM David Hildenbrand <david@...hat.com> wrote:
>
> On 23.11.21 18:17, Shakeel Butt wrote:
> > On Tue, Nov 23, 2021 at 8:57 AM David Hildenbrand <david@...hat.com> wrote:
> >>
> > [...]
> >>>>
> >>>> I do wonder which these locking contexts are exactly, and if we could
> >>>> also do the same thing on ordinary munmap -- because I assume it can be
> >>>> similarly problematic for some applications.
> >>>
> >>> This is a good question regarding munmap. One main difference is
> >>> munmap takes mmap_lock in write mode and usually performance critical
> >>> applications avoid such operations.
> >>
> >> Maybe we can extend it too most page zapping, if that makes things simpler.
> >>
> >
> > Do you mean doing sync THP split for most of page zapping functions
> > (but only if that makes things simpler)?
> >
>
> Yes -- if there are no downsides.
>

I will try. At the moment the assumption of "Not null zap_details
implies leave swap entries" is giving me a headache.

Thanks for the suggestions and your time.