refill_freelist() and page_launder()

refill_freelist() and page_launder()

[Marcelo Tosatti]

Linus, 

refill_freelist() (fs/buffer.c) calls page_launder(GFP_BUFFER) after
syncing some of the oldest dirty buffers.

As fair as I can see, that used to make sense because clean pages could be
freed with page_launder(GFP_BUFFER) -- this could avoid a potential sleep
on kswapd when trying to allocate a buffer page with grow_buffers().

But now __alloc_pages will not wait kswapd anymore. 

Instead the running thread will free clean pages only when it has to call
page_launder() itself because kswapd could not keep up.

Could you remove the call to page_launder() and the if() on top on your
tree ? 

Come one, doing by hand its easier than a patch.

Here's the function:

/*
 * We used to try various strange things. Let's not.
 * We'll just try to balance dirty buffers, and possibly
 * launder some pages.
 */
static void refill_freelist(int size)
{
        balance_dirty(NODEV);
        if (free_shortage())
                page_launder(GFP_BUFFER, 0);
        grow_buffers(size);
}

grow_buffers() calls alloc_page(GFP_BUFFER).