From: David Woodhouse <dwmw2@infradead.org>
To: Julien Grall <julien@xen.org>,
George Dunlap <george.dunlap@citrix.com>,
Jan Beulich <jbeulich@suse.com>,
Stewart Hildebrand <stewart.hildebrand@dornerworks.com>
Cc: Stefano Stabellini <sstabellini@kernel.org>, Wei Liu <wl@xen.org>,
Konrad Rzeszutek Wilk <konrad.wilk@oracle.com>,
George Dunlap <George.Dunlap@eu.citrix.com>,
Andrew Cooper <andrew.cooper3@citrix.com>,
Ian Jackson <ian.jackson@eu.citrix.com>,
Jeff Kubascik <jeff.kubascik@dornerworks.com>,
xen-devel@lists.xenproject.org
Subject: Re: [Xen-devel] [XEN PATCH v2 1/2] Check zone before merging adjacent blocks in heap
Date: Wed, 05 Feb 2020 11:36:41 +0000 [thread overview]
Message-ID: <5fb3a88ee20e7bea8418680f3353982424dd816b.camel@infradead.org> (raw)
In-Reply-To: <9d1c6e2b-f155-96f9-deeb-1b1f30c94081@xen.org>
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On Wed, 2020-02-05 at 10:22 +0000, Julien Grall wrote:
> However, I don't like the idea of relying on count_info == 0. Indeed,
> there are valid case where count_info == 0 because it means the page is
> inuse (PCC_state_inuse).
>
> It might be best if we introduce a new page state that would be the
> default value set in the frametable.
>
> 0 may be an option if we assign a different value to PGC_state_inuse but
> we would need to check if there are places relying on PGC_state_inuse ==
> 0. I know that assign_pages() does rely on it, I have sent a patch for
> it yesterday.
We'd need an extra bit for that.
Perhaps we could recognise that PGC_broken is not valid in combination
with some of the four PGC_state states, and take that bit back to turn
PGC_state into a 3-bit field, which could hold 8 states of which I
think we only currently need 7?
{ zero, inuse, offlining, offlining_broken, offline, offline_broken, free }
> Another option is to use an all 1s value and initialize the frametable
> to all 1s. But I am not entirely sure whether the allocator would be
> able to cope with it.
We'd zero it in init_heap_pages() for every page, and it would only be
still set to all 1s for pages from the boot allocator; as long as all
1s *is* proven to be an invalid state (I think it is); then the same
kind of trick checking unlikely(pg->count_info == -1) in the free
functions as in my earlier straw man, would probably work.
I think I prefer zero being the "untouched" state though, rather than
all 1s.
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next prev parent reply other threads:[~2020-02-05 11:37 UTC|newest]
Thread overview: 48+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-02-04 15:14 [Xen-devel] [XEN PATCH v2 1/2] Check zone before merging adjacent blocks in heap Stewart Hildebrand
2020-02-04 15:14 ` [Xen-devel] [DO NOT APPLY XEN PATCH v2 2/2] Test case for buddy allocator merging issue Stewart Hildebrand
2020-02-04 15:22 ` [Xen-devel] [XEN PATCH v2 1/2] Check zone before merging adjacent blocks in heap Jan Beulich
2020-02-04 15:37 ` George Dunlap
2020-02-05 9:50 ` David Woodhouse
2020-02-05 10:02 ` Jan Beulich
2020-02-05 10:24 ` David Woodhouse
2020-02-05 10:49 ` Jan Beulich
2020-02-05 11:23 ` David Woodhouse
2020-02-05 13:37 ` Jan Beulich
2020-02-05 14:12 ` David Woodhouse
2020-02-07 15:49 ` David Woodhouse
2020-02-07 15:57 ` [Xen-devel] [PATCH 1/2] xen/mm: fold PGC_broken into PGC_state bits David Woodhouse
2020-02-07 20:27 ` Julien Grall
2020-02-09 13:22 ` David Woodhouse
2020-02-09 17:59 ` Julien Grall
2020-03-17 21:39 ` David Woodhouse
2020-02-20 11:10 ` Jan Beulich
2020-03-17 21:52 ` David Woodhouse
2020-03-18 9:56 ` Jan Beulich
2020-03-18 12:31 ` Julien Grall
2020-03-18 13:23 ` Jan Beulich
2020-03-18 17:13 ` David Woodhouse
2020-03-19 8:49 ` Jan Beulich
2020-03-19 10:26 ` David Woodhouse
2020-03-19 11:59 ` Jan Beulich
2020-03-19 13:54 ` David Woodhouse
2020-03-19 14:46 ` Jan Beulich
2020-02-07 15:57 ` [Xen-devel] [PATCH 2/2] xen/mm: Introduce PG_state_uninitialised David Woodhouse
2020-02-07 16:30 ` Xia, Hongyan
2020-02-07 16:32 ` David Woodhouse
2020-02-07 16:40 ` Xia, Hongyan
2020-02-07 17:06 ` David Woodhouse
2020-02-07 18:04 ` David Woodhouse
2020-02-20 11:59 ` Jan Beulich
2020-02-20 13:27 ` Julien Grall
2020-03-17 22:15 ` David Woodhouse
2020-03-18 8:53 ` Paul Durrant
2020-03-18 10:10 ` Jan Beulich
2020-03-18 10:41 ` Paul Durrant
2020-03-18 11:12 ` Jan Beulich
2020-03-18 10:03 ` Jan Beulich
2020-03-18 12:11 ` David Woodhouse
2020-03-18 13:27 ` Jan Beulich
2020-02-05 10:22 ` [Xen-devel] [XEN PATCH v2 1/2] Check zone before merging adjacent blocks in heap Julien Grall
2020-02-05 10:32 ` David Woodhouse
2020-02-05 11:36 ` David Woodhouse [this message]
2020-02-04 15:37 ` Stewart Hildebrand
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