From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: linux-mm@kvack.org, Matthew Wilcox <mawilcox@microsoft.com>,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH v3 0/4] Split page_type out from mapcount
Date: Thu, 1 Mar 2018 09:00:16 +0100 [thread overview]
Message-ID: <20180301090016.01a54a5f@mschwideX1> (raw)
In-Reply-To: <20180301081750.42b135c3@mschwideX1>
On Thu, 1 Mar 2018 08:17:50 +0100
Martin Schwidefsky <schwidefsky@de.ibm.com> wrote:
> On Wed, 28 Feb 2018 14:31:53 -0800
> Matthew Wilcox <willy@infradead.org> wrote:
>
> > From: Matthew Wilcox <mawilcox@microsoft.com>
> >
> > I want to use the _mapcount field to record what a page is in use as.
> > This can help with debugging and we can also expose that information to
> > userspace through /proc/kpageflags to help diagnose memory usage (not
> > included as part of this patch set).
> >
> > First, we need s390 to stop using _mapcount for its own purposes;
> > Martin, I hope you have time to look at this patch. I must confess I
> > don't quite understand what the different bits are used for in the upper
> > nybble of the _mapcount, but I tried to replicate what you were doing
> > faithfully.
>
> Yeah, that is a nasty bit of code. On s390 we have 2K page tables (pte)
> but 4K pages. If we use full pages for the pte tables we waste 2K of
> memory for each of the tables. So we allocate 4K and split it into two
> 2K pieces. Now we have to keep track of the pieces to be able to free
> them again.
>
> I try to give your patch a spin today. It should be stand-alone, no ?
Ok, that seems to work just fine. System boots and survived some stress
without loosing memory.
Acked-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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next prev parent reply other threads:[~2018-03-01 8:00 UTC|newest]
Thread overview: 17+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-28 22:31 Matthew Wilcox
2018-02-28 22:31 ` [PATCH v3 1/4] s390: Use _refcount for pgtables Matthew Wilcox
2018-03-01 12:53 ` Kirill A. Shutemov
2018-03-01 14:04 ` Martin Schwidefsky
2018-03-01 14:28 ` Kirill A. Shutemov
2018-03-01 14:39 ` Martin Schwidefsky
2018-02-28 22:31 ` [PATCH v3 2/4] mm: Split page_type out from _map_count Matthew Wilcox
2018-02-28 22:31 ` [PATCH v3 3/4] mm: Mark pages allocated through vmalloc Matthew Wilcox
2018-02-28 22:31 ` [PATCH v3 4/4] mm: Mark pages in use for page tables Matthew Wilcox
2018-02-28 23:22 ` [PATCH v3 0/4] Split page_type out from mapcount Randy Dunlap
2018-03-01 1:31 ` Matthew Wilcox
2018-03-01 7:17 ` Martin Schwidefsky
2018-03-01 8:00 ` Martin Schwidefsky [this message]
2018-03-01 12:44 ` Kirill A. Shutemov
2018-03-01 14:47 ` Martin Schwidefsky
2018-03-01 14:50 ` Matthew Wilcox
2018-03-01 15:02 ` Martin Schwidefsky
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