Re: [PATCH -mm] mm, hugetlb: Pass fault address to no page handler

["Huang\, Ying" <ying.huang@intel.com>]

Mike Kravetz <mike.kravetz@oracle.com> writes:

> On 05/14/2018 05:57 PM, Huang, Ying wrote:
>> From: Huang Ying <ying.huang@intel.com>
>> 
>> This is to take better advantage of huge page clearing
>> optimization (c79b57e462b5d, "mm: hugetlb: clear target sub-page last
>> when clearing huge page").  Which will clear to access sub-page last
>> to avoid the cache lines of to access sub-page to be evicted when
>> clearing other sub-pages.  This needs to get the address of the
>> sub-page to access, that is, the fault address inside of the huge
>> page.  So the hugetlb no page fault handler is changed to pass that
>> information.  This will benefit workloads which don't access the begin
>> of the huge page after page fault.
>> 
>> With this patch, the throughput increases ~28.1% in vm-scalability
>> anon-w-seq test case with 88 processes on a 2 socket Xeon E5 2699 v4
>> system (44 cores, 88 threads).  The test case creates 88 processes,
>> each process mmap a big anonymous memory area and writes to it from
>> the end to the begin.  For each process, other processes could be seen
>> as other workload which generates heavy cache pressure.  At the same
>> time, the cache miss rate reduced from ~36.3% to ~25.6%, the
>> IPC (instruction per cycle) increased from 0.3 to 0.37, and the time
>> spent in user space is reduced ~19.3%
>
> Since this patch only addresses hugetlbfs huge pages, I would suggest
> making that more explicit in the commit message.

Sure.  Will revise it!

> Other than that, the changes look fine to me.
>
>> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
>
> Reviewed-by: Mike Kravetz <mike.kravetz@oracle.com>

Thanks!

Best Regards,
Huang, Ying