Re: [RFC] memory defragmentation to satisfy high order allocations

[IWAMOTO Toshihiro]

At Sat, 2 Oct 2004 15:33:49 -0300,
Marcelo Tosatti wrote:
> 
> On Sat, Oct 02, 2004 at 06:30:15PM +0900, Hirokazu Takahashi wrote:
> 3) At migrate_page_common you assume additional page references 
> (page_migratable returning -EAGAIN) means the code should try to writeout 
> the page.
> 
> Is that assumption always valid?
> 
> In theory there is no need to writeout pages when migrating them to 
> other zones - they will be copied and the dirty information retained (either
> in the PageDirty bit or radix tree tag). 

It's true only when page->private is NULL.  Otherwise writeback is
necessary to free buffer_head.

> I just noticed you do that on further patches (migrate_page_buffer), but AFAICS 
> the writeout remains. Why arent you using migrate_page_buffer yet?
> 
> I think the final aim should be to remove the need for "pageout()" 
> completly.

Are you going to implement migrate_page_buffer for every file system?
I don't think it's worthwhile.

> Questions: are there any documents on the memory hotplug userspace tools? 
> Where can I find them?
> 
> Are Iwamoto's test programs available?

I've put them at the following URL, but I doubt they are useful for
you; there are no documentation for them.

http://people.valinux.co.jp/~iwamoto/mh/tests/

--
IWAMOTO Toshihiro
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