Re: [PATCH] vmalloc: use rcu list iterator to reduce vmap_area_lock contention

[Eric Dumazet]

On Thu, 2014-05-29 at 15:22 +0900, Joonsoo Kim wrote:
> Richard Yao reported a month ago that his system have a trouble
> with vmap_area_lock contention during performance analysis
> by /proc/meminfo. Andrew asked why his analysis checks /proc/meminfo
> stressfully, but he didn't answer it.
> 
> https://lkml.org/lkml/2014/4/10/416
> 
> Although I'm not sure that this is right usage or not, there is a solution
> reducing vmap_area_lock contention with no side-effect. That is just
> to use rcu list iterator in get_vmalloc_info(). This function only needs
> values on vmap_area structure, so we don't need to grab a spinlock.
> 
> Reported-by: Richard Yao <ryao@xxxxxxxxxx>
> Signed-off-by: Joonsoo Kim <iamjoonsoo.kim@xxxxxxx>

Nice, I was considering the same

Acked-by: Eric Dumazet <edumazet@xxxxxxxxxx>



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