fs/proc/task_mmu: add fast paths to get/clear PAGE_IS_WRITTEN flag

Adding fast code paths to handle specifically only get and/or clear
operation of PAGE_IS_WRITTEN, increases its performance by 0-35%.  The
results of some test cases are given below:

Test-case-1
t1 = (Get + WP) time
t2 = WP time
                       t1            t2
Without this patch:    140-170mcs    90-115mcs
With this patch:       110mcs        80mcs
Worst case diff:       35% faster    30% faster

Test-case-2
t3 = atomic Get and WP
                      t3
Without this patch:   120-140mcs
With this patch:      100-110mcs
Worst case diff:      21% faster

Link: https://lkml.kernel.org/r/[email protected]
Signed-off-by: Muhammad Usama Anjum <[email protected]>
Cc: Alex Sierra <[email protected]>
Cc: Al Viro <[email protected]>
Cc: Andrei Vagin <[email protected]>
Cc: Axel Rasmussen <[email protected]>
Cc: Christian Brauner <[email protected]>
Cc: Cyrill Gorcunov <[email protected]>
Cc: Dan Williams <[email protected]>
Cc: David Hildenbrand <[email protected]>
Cc: Greg Kroah-Hartman <[email protected]>
Cc: Gustavo A. R. Silva <[email protected]>
Cc: "Liam R. Howlett" <[email protected]>
Cc: Matthew Wilcox <[email protected]>
Cc: Michal Miroslaw <[email protected]>
Cc: Michał Mirosław <[email protected]>
Cc: Mike Rapoport (IBM) <[email protected]>
Cc: Nadav Amit <[email protected]>
Cc: Pasha Tatashin <[email protected]>
Cc: Paul Gofman <[email protected]>
Cc: Peter Xu <[email protected]>
Cc: Shuah Khan <[email protected]>
Cc: Suren Baghdasaryan <[email protected]>
Cc: Vlastimil Babka <[email protected]>
Cc: Yang Shi <[email protected]>
Cc: Yun Zhou <[email protected]>
Signed-off-by: Andrew Morton <[email protected]>

0 files changed, 0 insertions, 0 deletions