Re: [PATCH 06/33] readahead: refactor __do_page_cache_readahead()

[Wu Fengguang]

On Thu, May 25, 2006 at 09:30:39AM -0700, Andrew Morton wrote:
> Wu Fengguang <wfg@xxxxxxxxxxxxxxxx> wrote:
> >
> > Add look-ahead support to __do_page_cache_readahead(),
> > which is needed by the adaptive read-ahead logic.
> 
> You'd need to define "look-ahead support" before telling us you've added it ;)
> 
> > @@ -302,6 +303,8 @@ __do_page_cache_readahead(struct address
> >  			break;
> >  		page->index = page_offset;
> >  		list_add(&page->lru, &page_pool);
> > +		if (page_idx == nr_to_read - lookahead_size)
> > +			__SetPageReadahead(page);
> >  		ret++;
> >  	}
> 
> OK.  But the __SetPageFoo() things still give me the creeps.

Hehe, updated to SetPageReadahead().

> OT: look:
> 
> 		read_unlock_irq(&mapping->tree_lock);
> 		page = page_cache_alloc_cold(mapping);
> 		read_lock_irq(&mapping->tree_lock);
> 
> we should have a page allocation function which just allocates a page from
> this CPU's per-cpu-pages magazine, and fails if the magazine is empty:
> 
> 		page = 	alloc_pages_local(mapping_gfp_mask(x)|__GFP_COLD);
> 		if (!page) {
> 			read_unlock_irq(&mapping->tree_lock);
> 			/*
> 			 * This will refill the per-cpu-pages magazine
> 			 */
> 			page = page_cache_alloc_cold(mapping);
> 			read_lock_irq(&mapping->tree_lock);
> 		}

Seems good, except for the alloc_pages_local() not being able to
spread memory among nodes as page_cache_alloc_cold() do.

Wu
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