Hi, Laura,
I has replaced the evict_bh_lrus(bh) with invalidate_bh_lrus() and it is working fine.
How about submit new patch with invalidate_bh_lrus()?
I would appreciate it.
2014-07-02 오후 2:46, Andrew Morton 쓴 글:
On Mon, 30 Jun 2014 19:02:45 -0700 Laura Abbott <lauraa@xxxxxxxxxxxxxx> wrote:
On 6/30/2014 6:07 PM, Gioh Kim wrote:
Hi,Laura.
I have a question.
Does the __evict_bh_lru() not need bh_lru_lock()?
The get_cpu_var() has already preenpt_disable() and can prevent other thread.
But get_cpu_var cannot prevent IRQ context such like page-fault.
I think if a page-fault occured and a file is read in IRQ context it can change cpu-lru.
Is my concern correct?
__evict_bh_lru is called via on_each_cpu_cond which I believe will disable irqs.
I based the code on the existing invalidate_bh_lru which did not take the bh_lru_lock
either. It's possible I missed something though.
I fear that running on_each_cpu() within try_to_free_buffers() is going
to be horridly expensive in some cases.
Maybe CMA can use invalidate_bh_lrus() to shoot down everything before
trying the allocation attempt. That should increase the success rate
greatly and doesn't burden page reclaim. The bh LRU isn't terribly
important from a performance point of view, so emptying it occasionally
won't hurt.
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