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

[David Rientjes <rientjes@google.com>]

On Tue, 15 May 2018, 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%
> 
> Signed-off-by: "Huang, Ying" <ying.huang@intel.com>
> Cc: Andrea Arcangeli <aarcange@redhat.com>
> Cc: "Kirill A. Shutemov" <kirill.shutemov@linux.intel.com>
> Cc: Andi Kleen <andi.kleen@intel.com>
> Cc: Jan Kara <jack@suse.cz>
> Cc: Michal Hocko <mhocko@suse.com>
> Cc: Matthew Wilcox <mawilcox@microsoft.com>
> Cc: Hugh Dickins <hughd@google.com>
> Cc: Minchan Kim <minchan@kernel.org>
> Cc: Shaohua Li <shli@fb.com>
> Cc: Christopher Lameter <cl@linux.com>
> Cc: "Aneesh Kumar K.V" <aneesh.kumar@linux.vnet.ibm.com>
> Cc: Punit Agrawal <punit.agrawal@arm.com>
> Cc: Anshuman Khandual <khandual@linux.vnet.ibm.com>

Acked-by: David Rientjes <rientjes@google.com>