[lttng-dev] [-stable 3.8.1 performance regression] madvise POSIX_FADV_DONTNEED

Yannick Brosseau yannick.brosseau at gmail.com
Wed Jul 3 14:47:58 EDT 2013

On 2013-07-03 04:47, Mel Gorman wrote:
>> Given it is just a hint, we should be allowed to perform page
>> > deactivation lazily. Is there any fundamental reason to wait for worker
>> > threads on each CPU to complete their lru drain before returning from
>> > fadvise() to user-space ?
>> > 
> Only to make sure they pages are actually dropped as requested. The reason
> the wait was introduced in the first place was that page cache was filling
> up even with the fadvise calls and causing disruption. In 3.11 disruption
> due to this sort of parallel IO should be reduced but making fadvise work
> properly is reasonable in itself. Was that patch I posted ever tested or
> did I manage to miss it?
I did test it. On our test case, we get a worst result with it.


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