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android_kernel_motorola_sm6225/fs/proc
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Alexey Dobriyan f7a5f132b4 proc: faster /proc/*/status 
top(1) opens the following files for every PID:

	/proc/*/stat
	/proc/*/statm
	/proc/*/status

This patch switches /proc/*/status away from seq_printf().
The result is 13.5% speedup.

Benchmark is open("/proc/self/status")+read+close 1.000.000 million times.

				BEFORE
$ perf stat -r 10 taskset -c 3 ./proc-self-status

 Performance counter stats for 'taskset -c 3 ./proc-self-status' (10 runs):

      10748.474301      task-clock (msec)         #    0.954 CPUs utilized            ( +-  0.91% )
                12      context-switches          #    0.001 K/sec                    ( +-  1.09% )
                 1      cpu-migrations            #    0.000 K/sec
               104      page-faults               #    0.010 K/sec                    ( +-  0.45% )
    37,424,127,876      cycles                    #    3.482 GHz                      ( +-  0.04% )
     8,453,010,029      stalled-cycles-frontend   #   22.59% frontend cycles idle     ( +-  0.12% )
     3,747,609,427      stalled-cycles-backend    #  10.01% backend cycles idle       ( +-  0.68% )
    65,632,764,147      instructions              #    1.75  insn per cycle
                                                  #    0.13  stalled cycles per insn  ( +-  0.00% )
    13,981,324,775      branches                  # 1300.773 M/sec                    ( +-  0.00% )
       138,967,110      branch-misses             #    0.99% of all branches          ( +-  0.18% )

      11.263885428 seconds time elapsed                                          ( +-  0.04% )
      ^^^^^^^^^^^^

				AFTER
$ perf stat -r 10 taskset -c 3 ./proc-self-status

 Performance counter stats for 'taskset -c 3 ./proc-self-status' (10 runs):

       9010.521776      task-clock (msec)         #    0.925 CPUs utilized            ( +-  1.54% )
                11      context-switches          #    0.001 K/sec                    ( +-  1.54% )
                 1      cpu-migrations            #    0.000 K/sec                    ( +- 11.11% )
               103      page-faults               #    0.011 K/sec                    ( +-  0.60% )
    32,352,310,603      cycles                    #    3.591 GHz                      ( +-  0.07% )
     7,849,199,578      stalled-cycles-frontend   #   24.26% frontend cycles idle     ( +-  0.27% )
     3,269,738,842      stalled-cycles-backend    #  10.11% backend cycles idle       ( +-  0.73% )
    56,012,163,567      instructions              #    1.73  insn per cycle
                                                  #    0.14  stalled cycles per insn  ( +-  0.00% )
    11,735,778,795      branches                  # 1302.453 M/sec                    ( +-  0.00% )
        98,084,459      branch-misses             #    0.84% of all branches          ( +-  0.28% )

       9.741247736 seconds time elapsed                                          ( +-  0.07% )
       ^^^^^^^^^^^

Link: http://lkml.kernel.org/r/20160806125608.GB1187@p183.telecom.by
Signed-off-by: Alexey Dobriyan <adobriyan@gmail.com>
Cc: Joe Perches <joe@perches.com>
Cc: Andi Kleen <andi@firstfloor.org>
Cc: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
2016-10-07 18:46:30 -07:00
..
array.c proc: faster /proc/*/status 2016-10-07 18:46:30 -07:00
base.c Merge branch 'linus' into x86/asm, to pick up recent fixes 2016-09-15 08:24:53 +02:00
cmdline.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
consoles.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
cpuinfo.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
devices.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
fd.c switch all procfs directories ->iterate_shared() 2016-05-02 19:49:30 -04:00
fd.h proc: Move proc_fd() to fs/proc/fd.h 2013-05-01 17:29:39 -04:00
generic.c proc: make proc entries inherit ownership from parent 2016-08-14 21:07:20 -07:00
inode.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2016-07-29 15:54:19 -07:00
internal.h proc: Convert proc_mount to use mount_ns. 2016-06-23 15:41:54 -05:00
interrupts.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
Kconfig fs, proc: add help for CONFIG_PROC_CHILDREN 2015-07-17 16:39:52 -07:00
kcore.c fs/proc/kcore.c: Add bounce buffer for ktext data 2016-09-20 13:32:49 -07:00
kmsg.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
loadavg.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
Makefile fs/proc: Add compiler check for -Wno-override-init to support gcc < 4.2 2016-08-03 12:45:23 -04:00
meminfo.c proc, meminfo: use correct helpers for calculating LRU sizes in meminfo 2016-08-11 16:58:13 -07:00
namespaces.c switch all procfs directories ->iterate_shared() 2016-05-02 19:49:30 -04:00
nommu.c vfs: add seq_file_path() helper 2015-06-23 18:01:07 -04:00
page.c mm: rename _count, field of the struct page, to _refcount 2016-05-19 19:12:14 -07:00
proc_net.c proc: make proc entries inherit ownership from parent 2016-08-14 21:07:20 -07:00
proc_sysctl.c Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/ebiederm/user-namespace 2016-10-06 09:52:23 -07:00
proc_tty.c proc: remove proc_tty_ldisc variable 2014-08-08 15:57:22 -07:00
root.c proc: Convert proc_mount to use mount_ns. 2016-06-23 15:41:54 -05:00
self.c wrappers for ->i_mutex access 2016-01-22 18:04:28 -05:00
softirqs.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
stat.c procfs: avoid 32-bit time_t in /proc/*/stat 2016-08-02 17:31:41 -04:00
task_mmu.c fs/proc/task_mmu.c: make the task_mmu walk_page_range() limit in clear_refs_write() obvious 2016-10-07 18:46:28 -07:00
task_nommu.c proc: revert /proc/<pid>/maps [stack:TID] annotation 2016-02-03 08:28:43 -08:00
thread_self.c wrappers for ->i_mutex access 2016-01-22 18:04:28 -05:00
uptime.c cputime: Default implementation of nsecs -> cputime conversion 2014-03-13 15:56:43 +01:00
version.c fs/proc: don't use module_init for non-modular core code 2014-01-23 16:37:02 -08:00
vmcore.c crash_dump: Add vmcore_elf32_check_arch 2016-05-13 14:01:59 +02:00