Re: [patch 2/3] mm: speculative get_page

[Nick Piggin <nickpiggin@yahoo.com.au>]

Christoph Lameter wrote:
> Looks like the NoNewRefs flag is mostly == 
> spin_is_locked(mapping->tree_lock)? Would it not be better to check the 
> tree_lock?
> 

Well there are other uses for the tree_lock (eg. tag operations)
which do not need the "no new references" guarantee.

> 
> 
>>--- linux-2.6.orig/mm/migrate.c
>>+++ linux-2.6/mm/migrate.c
>> 
>>+	SetPageNoNewRefs(page);
>> 	write_lock_irq(&mapping->tree_lock);
> 
> 
> A dream come true! If this is really working as it sounds then we can 
> move the SetPageNoNewRefs up and avoid the final check under 
> mapping->tree_lock. Then keep SetPageNoNewRefs until the page has been 
> copied. It would basically play the same role as locking the page.
> 

Yes we could do that but at this stage I wouldn't like to seperate
SetPageNoNewRefs from tree_lock, as it is replacing a traditional
guarantee that tree_lock no longer provides.

-- 
SUSE Labs, Novell Inc.
Send instant messages to your online friends http://au.messenger.yahoo.com 

--
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>