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Re: pagebuf page cleaner and page aging

To: Rajagopal Ananthanarayanan <ananth@xxxxxxx>
Subject: Re: pagebuf page cleaner and page aging
From: Christoph Hellwig <hch@xxxxxxxxxx>
Date: Fri, 19 Jan 2001 19:44:33 +0100
Cc: Christoph Hellwig <hch@xxxxxxxxxx>, Marcelo Tosatti <marcelo@xxxxxxxxxxxxxxxx>, linux-xfs@xxxxxxxxxxx
In-reply-to: <3A688567.9CC4CE7A@sgi.com>; from ananth@sgi.com on Fri, Jan 19, 2001 at 10:20:23AM -0800
References: <200101191510.f0JFAHs02250@jen.americas.sgi.com> <Pine.LNX.4.21.0101191123270.5416-100000@freak.distro.conectiva> <20010119183803.A23862@caldera.de> <3A688567.9CC4CE7A@sgi.com>
Sender: owner-linux-xfs@xxxxxxxxxxx
On Fri, Jan 19, 2001 at 10:20:23AM -0800, Rajagopal Ananthanarayanan wrote:
> 
> There's been several mail exchanges already on this thread.
> Let me try to summarize:
> 
> 1. The page cleaner should walk the dirty list of pages.

Yepp.

> 2. There are 2 reasons to start write-out earlier than on
>    just memory pressure/aging information alone. (a) to minimize
>    data lost due to delalloc pages not written to disk (b) to minimize
>    write pressure on the disk .. you don't want to fill-up a 1GB system
>    with delalloc pages & starting to write out at 20 MB/sec to disk.

(b) should be handled in a generic way (by the mm subsys), but I'm not
sure how to do (a).

> 3. Its almost tempting to make kswapd do the delalloc conversions,
>    since it walks the inactive dirty list through page_launder().
>    However, if you think about it, the conversion is an operation
>    that logically sits between make a page delalloc & writing it out to
>    disk. IMO, we need a seperate daemon to perform the conversions.

Agreed.  Again it should be handled outside XFS, e.g. my generic kiobuf
address_space methods start using delayed allocation (in a hairy way ...).

        Christoph

-- 
Whip me.  Beat me.  Make me maintain AIX.

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