Paul E. McKenney wrote:

quoted text
>>> So on your these large boxes, read-only cachelines are preferentially
>>> ejected from the cache, so that one should write to per-CPU data
>>> occasionally to keep it resident?  Or is the issue the long RCU grace
>>> periods which allow the structure being freed to age out of all relevant
>>> caches?  (My guess would be the second.)
>> The issue are the RCU grace period that are generally long enough to make the
>> cacheline fall out of all caches.
> 
> Would it make sense to push the freed-by-RCU memory further up the
> hierarchy, so that such memory is not mistaken for recently freed
> hot-in-cache memory?

That would mean passing a gfp flag like __GFP_COLD on free from RCU? Or how
would that work at the higher levels?


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