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

Wu Fengguang
2006-05-26T07:13:39Z

On Thu, May 25, 2006 at 09:30:39AM -0700, Andrew Morton wrote:
> Wu Fengguang <wfg@mail.ustc.edu.cn> 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