From: Martin Schwidefsky <schwidefsky@de.ibm.com>
To: Matthew Wilcox <willy@infradead.org>
Cc: "Kirill A. Shutemov" <kirill@shutemov.name>,
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 16:02:58 +0100 [thread overview]
Message-ID: <20180301160258.6a619212@mschwideX1> (raw)
In-Reply-To: <20180301145058.GA19662@bombadil.infradead.org>
On Thu, 1 Mar 2018 06:50:58 -0800
Matthew Wilcox <willy@infradead.org> wrote:
> On Thu, Mar 01, 2018 at 03:44:12PM +0300, Kirill A. Shutemov wrote:
> > On Thu, Mar 01, 2018 at 08:17:50AM +0100, Martin Schwidefsky wrote:
> > > 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.
> >
> > Have you considered to use slab for page table allocation instead?
> > IIRC some architectures practice this already.
>
> You're not allowed to do that any more. Look at pgtable_page_ctor(),
> or rather ptlock_init().
Oh yes, I forgot about the ptl. This takes up some fields in struct page
which the slab/slub cache want to use as well.
--
blue skies,
Martin.
"Reality continues to ruin my life." - Calvin.
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prev parent reply other threads:[~2018-03-01 15:03 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
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 [this message]
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