From: Matthew Wilcox <willy@infradead.org>
To: "Kirill A. Shutemov" <kirill@shutemov.name>
Cc: linux-mm@kvack.org, Matthew Wilcox <mawilcox@microsoft.com>
Subject: Re: [PATCH] mm: Split page_type out from _map_count
Date: Fri, 9 Feb 2018 05:49:42 -0800 [thread overview]
Message-ID: <20180209134942.GB16666@bombadil.infradead.org> (raw)
In-Reply-To: <20180209105132.hhkjoijini3f74fz@node.shutemov.name>
On Fri, Feb 09, 2018 at 01:51:32PM +0300, Kirill A. Shutemov wrote:
> On Wed, Feb 07, 2018 at 01:30:47PM -0800, Matthew Wilcox wrote:
> > From: Matthew Wilcox <mawilcox@microsoft.com>
> >
> > We're already using a union of many fields here, so stop abusing the
> > _map_count and make page_type its own field. That implies renaming some
> > of the machinery that creates PageBuddy, PageBalloon and PageKmemcg;
> > bring back the PG_buddy, PG_balloon and PG_kmemcg names.
>
> Sounds reasonable to me.
>
> > Also, the special values don't need to be (and probably shouldn't be) powers
> > of two, so renumber them to just start at -128.
>
> Are you sure about this? Is it guarantee that we would not need in the
> future PG_buddy|PG_kmemcg for instance?
>
> I guess we may want to make it a bitfield. In negative space it's kinda
> interesting. :)
Far too interesting ;-) We still wouldn't want it to be powers of two ...
We'd want to do something like:
#define PAGE_TYPE_BASE 0xfffff000
#define PG_buddy 0x00000080
#define PG_balloon 0x00000100
#define PG_kmemcg 0x00000200
#define PG_pte 0x00000400
... etc ...
I think that's a worthwhile improvement, particularly since I think
PG_kmemcg might want to be a completely independent flag from everything
else ("This is a page allocated for userspace PTEs, so it's both a kmemcg
page and a PTE page").
I'll respin the patch. Thanks!
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@kvack.org. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@kvack.org"> email@kvack.org </a>
next prev parent reply other threads:[~2018-02-09 13:49 UTC|newest]
Thread overview: 8+ messages / expand[flat|nested] mbox.gz Atom feed top
2018-02-07 21:30 [PATCH] mm: Split page_type out from _map_count Matthew Wilcox
2018-02-09 10:51 ` Kirill A. Shutemov
2018-02-09 13:49 ` Matthew Wilcox [this message]
2018-02-09 15:28 ` [PATCH v2] " Matthew Wilcox
2018-02-09 18:43 ` Dave Hansen
2018-02-09 19:04 ` Christopher Lameter
2018-02-09 19:28 ` Matthew Wilcox
2018-02-10 5:00 ` [PATCH] " kbuild test robot
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20180209134942.GB16666@bombadil.infradead.org \
--to=willy@infradead.org \
--cc=kirill@shutemov.name \
--cc=linux-mm@kvack.org \
--cc=mawilcox@microsoft.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for NNTP newsgroup(s).