Re: [PATCH] Page eviction support in vmscan.c

[Joel Schopp <jschopp@austin.ibm.com>]

Christoph sent this to @vger.kernel.org instead of @kvack.org.  I assume 
he'll resend the original to this list.  Sorry if this messes up threading.

> This patch adds functions that allow the eviction of pages to swap space.
> Page eviction may be useful to migrate pages, suspend programs or for
> ummapping single pages (useful for faulty pages or pages with soft ECC
> failures)

I'm curious what use motivated you to write it.  I think for migration
it would usually make more sense to let the swapper free up LRU memory
and then do a memory to memory migration.  But I'm not really a
migration expert


> swapout_pages does its best to swapout the pages and does multiple passes over the list.
> However, swapout_pages may not be able to evict all pages for a variety of reasons.

Have you thought about using this in combination with the fragmentation
avoidance patches Mel has been posting?  __GFP_USER flag that adds would
go a long way toward determining what can and can't be swapped out.  We
use that for migration with great success.  I'd assume the criteria for
swapout and migration are pretty similar.

>  /*
> + * Swapout evicts the pages on the list to swap space.
> + * This is essentially a dumbed down version of shrink_list

Have you thought about reusing code from shrink list without duplicating
it?  That is a whole lot of duplicated code to maintain twice.

> +		if (PageDirty(page)) {
> +			/* Page is dirty, try to write it out here */
> +			switch(pageout(page, mapping)) {
> +			case PAGE_KEEP:
> +			case PAGE_ACTIVATE:
> +				goto retry_later_locked;
> +			case PAGE_SUCCESS:
> +				goto retry_later;
> +			case PAGE_CLEAN:
> +				; /* try to free the page below */
> +			}
> +                }

Tabs vs spaces?

> +
> +		list_del(&page->lru);
> +                unlock_page(page);
> +		put_page(page);
> +                continue;

Tabs vs spaces?





--
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>