Messages in this thread |  | | Date | Thu, 6 Feb 2014 14:58:21 -0800 (PST) | From | David Rientjes <> | Subject | Re: [RFC PATCH V5] mm readahead: Fix readahead fail for no local memory and limit readahead pages |
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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); > > }
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