On Wed, 22 Jan 2014 16:23:45 +0530 Raghavendra K T <raghavendra.kt@xxxxxxxxxxxxxxxxxx> wrote:
> max_sane_readahead returns zero on the cpu having no local memory
> node. Fix that by returning a sanitized number of pages viz.,
> minimum of (requested pages, 4k)
um, fix what? The changelog should describe the user-visible impact of
the current implementation. There are a whole bunch of reasons for
this, but I tire of typing them in day after day after day.
> --- a/mm/readahead.c
> +++ b/mm/readahead.c
> @@ -237,14 +237,32 @@ int force_page_cache_readahead(struct address_space *mapping, struct file *filp,
> return ret;
> }
>
> +#define MAX_REMOTE_READAHEAD 4096UL
> /*
> * Given a desired number of PAGE_CACHE_SIZE readahead pages, return a
> * sensible upper limit.
> */
> unsigned long max_sane_readahead(unsigned long nr)
> {
> - return min(nr, (node_page_state(numa_node_id(), NR_INACTIVE_FILE)
> - + node_page_state(numa_node_id(), NR_FREE_PAGES)) / 2);
> + unsigned long local_free_page;
> + int nid;
> +
> + nid = numa_node_id();
> + if (node_present_pages(nid)) {
> + /*
> + * We sanitize readahead size depending on free memory in
> + * the local node.
> + */
> + local_free_page = node_page_state(nid, NR_INACTIVE_FILE)
> + + node_page_state(nid, NR_FREE_PAGES);
> + return min(nr, local_free_page / 2);
> + }
> + /*
> + * Readahead onto remote memory is better than no readahead when local
> + * numa node does not have memory. We limit the readahead to 4k
> + * pages though to avoid trashing page cache.
> + */
> + return min(nr, MAX_REMOTE_READAHEAD);
> }
Looks reasonable to me. Please send along a fixed up changelog.
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