From: David Wragg <dpw@doc.ic.ac.uk>
To: "Stephen C. Tweedie" <sct@redhat.com>
Cc: "Eric W. Biederman" <ebiederm@xmission.com>,
linux-kernel@vger.kernel.org, linux-mm@kvack.org
Subject: Re: limit on number of kmapped pages
Date: 25 Jan 2001 23:53:16 +0000 [thread overview]
Message-ID: <y7rwvbjmbo3.fsf@sytry.doc.ic.ac.uk> (raw)
In-Reply-To: "Stephen C. Tweedie"'s message of "Thu, 25 Jan 2001 18:16:21 +0000"
"Stephen C. Tweedie" <sct@redhat.com> writes:
> On Wed, Jan 24, 2001 at 12:35:12AM +0000, David Wragg wrote:
> >
> > > And why do the pages need to be kmapped?
> >
> > They only need to be kmapped while data is being copied into them.
>
> But you only need to kmap one page at a time during the copy. There
> is absolutely no need to copy the whole chunk at once.
The chunks I'm copying are always smaller than a page. Usually they
are a few hundred bytes.
Though because I'm copying into the pages in a bottom half, I'll have
to use kmap_atomic. After a page is filled, it is put into the page
cache. So they have to be allocated with page_cache_alloc(), hence
__GFP_HIGHMEM and the reason I'm bothering with kmap at all.
David Wragg
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prev parent reply other threads:[~2001-01-25 23:53 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
[not found] <y7rsnmav0cv.fsf@sytry.doc.ic.ac.uk>
2001-01-23 18:23 ` Eric W. Biederman
2001-01-24 0:35 ` David Wragg
2001-01-24 2:03 ` Benjamin C.R. LaHaise
2001-01-24 10:09 ` David Wragg
2001-01-24 14:27 ` Eric W. Biederman
2001-01-25 10:06 ` Random thoughts on sustained write performance Daniel Phillips
[not found] ` <y7rsnm7mai7.fsf@sytry.doc.ic.ac.uk>
[not found] ` <01012615062602.20169@gimli>
2001-01-27 13:50 ` David Wragg
2001-01-27 17:23 ` Daniel Phillips
2001-01-27 21:23 ` David Wragg
2001-01-25 18:16 ` limit on number of kmapped pages Stephen C. Tweedie
2001-01-25 23:53 ` David Wragg [this message]
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