Re: [PATCH RFC] mm: lru milestones, timestamps and ages

[Mel Gorman <mgorman@suse.de>]

On Tue, Apr 30, 2013 at 03:02:14PM +0400, Konstantin Khlebnikov wrote:
> +static inline bool
> +is_lru_milestone(struct lruvec *lruvec, struct list_head *list)
> +{
> +	return unlikely(list >= &lruvec->milestones[0][0].lru &&
> +			list <  &lruvec->milestones[NR_EVICTABLE_LRU_LISTS]
> +						   [NR_LRU_MILESTONES].lru);
> +}
> +

Not reviewing properly yet, just taking a quick look out of interest but
this check may be delicate.  32-bit x86 machines start the kernel direct
mapping at 0xC0000000 so milestones[0][0].lru will have some value betewen
0xC0000000 and 0xFFFFFFFF. HZ=250 on my distro config so after 0xC0000000
jiffies or a bit over 149 days of uptime, it looks like there will be a
window where LRU entries look like milestones. If I'm right, that is
bound to cause problems.

-- 
Mel Gorman
SUSE Labs

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