On Thu, 6 Feb 2014, Andrew Morton wrote:
> > --- 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 you're intending this to be cached for your calls into
node_page_state() you need nid = ACCESS_ONCE(numa_node_id()).
What's the downside of just using numa_mem_id() here instead which is
usually "local memory to this memoryless node cpu" and forget about
testing node_present_pages(nid)?
> > + 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);
> > }
--
To unsubscribe, send a message with 'unsubscribe linux-mm' in
the body to majordomo@xxxxxxxxx. For more info on Linux MM,
see: http://www.linux-mm.org/ .
Don't email: <a href=mailto:"dont@xxxxxxxxx";> email@xxxxxxxxx </a>