From: Andrew Morton <akpm@linux-foundation.org>
To: Johannes Weiner <hannes@cmpxchg.org>
Cc: Rusty Russell <rusty@rustcorp.com.au>,
LKML <linux-kernel@vger.kernel.org>,
Nick Piggin <npiggin@suse.de>,
Stewart Smith <stewart@flamingspork.com>,
linux-mm@kvack.org, linux-arch@vger.kernel.org
Subject: Re: [patch 1/2] mm: fincore()
Date: Fri, 15 Feb 2013 13:27:38 -0800 [thread overview]
Message-ID: <20130215132738.c85c9eda.akpm@linux-foundation.org> (raw)
In-Reply-To: <20130215063450.GA24047@cmpxchg.org>
On Fri, 15 Feb 2013 01:34:50 -0500
Johannes Weiner <hannes@cmpxchg.org> wrote:
> + * The status is returned in a vector of bytes. The least significant
> + * bit of each byte is 1 if the referenced page is in memory, otherwise
> + * it is zero.
Also, this is going to be dreadfully inefficient for some obvious cases.
We could address that by returning the info in some more efficient
representation. That will be run-length encoded in some fashion.
The obvious way would be to populate an array of
struct page_status {
u32 present:1;
u32 count:31;
};
or whatever.
Another way would be to define the syscall so it returns "number of
pages present/absent starting at offset `start'". In other words, one
call to fincore() will return a single `struct page_status'. Userspace
can then walk through the file and generate the full picture, if needed.
This also gets inefficient in obvious cases, but it's not as obviously
bad?
next prev parent reply other threads:[~2013-02-15 21:27 UTC|newest]
Thread overview: 22+ messages / expand[flat|nested] mbox.gz Atom feed top
2013-02-11 3:13 RFC: mincore: add a bit to indicate a page is dirty Rusty Russell
2013-02-11 16:27 ` Johannes Weiner
2013-02-11 22:12 ` Andrew Morton
2013-02-12 5:44 ` Rusty Russell
2013-02-15 6:34 ` [patch 1/2] mm: fincore() Johannes Weiner
2013-02-15 20:39 ` David Miller
2013-02-15 21:14 ` Andrew Morton
2013-02-15 22:28 ` Johannes Weiner
2013-02-15 22:34 ` Andrew Morton
2013-02-15 21:27 ` Andrew Morton [this message]
2013-02-15 23:13 ` Johannes Weiner
2013-02-15 23:42 ` Andrew Morton
2013-02-16 4:23 ` Rusty Russell
2013-02-17 22:51 ` Johannes Weiner
2013-02-17 22:54 ` Andrew Morton
2013-05-29 14:53 ` Andres Freund
2013-05-29 17:32 ` Johannes Weiner
2013-05-29 17:52 ` Andres Freund
2013-02-18 5:41 ` Rusty Russell
2013-02-19 10:25 ` Simon Jeons
2013-02-15 6:35 ` [patch 2/2] x86-64: hook up fincore() syscall Johannes Weiner
2013-02-12 5:49 ` RFC: mincore: add a bit to indicate a page is dirty Rusty Russell
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