Re: [PATCH 30/45] vmscan: lumpy pageout

[Nikita Danilov <danilov@gmail.com>]

2009/10/7 Wu Fengguang <fengguang.wu@intel.com>:

[...]

> +                */
> +               if (current_is_kswapd() &&
> +                   bdi_cap_writeback_dirty(mapping->backing_dev_info) &&
> +                   !mapping->a_ops->writepages) {
> +                       wbc.range_start = (page->index + 1) << PAGE_CACHE_SHIFT;
> +                       wbc.nr_to_write = LUMPY_PAGEOUT_PAGES - 1;
> +                       generic_writepages(mapping, &wbc);
> +                       iput(inode);
> +               }
> +
> +               /*

One potential problem with this is that generic_writepages() waits on
page locks and this can stall kswapd (always bad). This can be worked
around by replacing lock_page() with trylock_page() conditionally on
wbc->for_reclaim (or wbc->nonblocking?), but then, this almost look
like a separate function would be better.

On a good side, it seems I was wrong and pageout calls iput() already:
shrink_slab()->prune_icache()->iput().

Thank you,
Nikita.
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