Apollyon musings, truncated.

[poondog: adapt for flo too]
Signed-off-by: poondog <markj338@gmail.com>
From 7747bd4bceb3079572695d3942294a6c7b265557 Mon Sep 17 00:00:00 2001 From: Dave Chinner <dchinner@redhat.com> Date: Tue, 02 Jul 2013 12:38:35 +0000 Subject: sync: don't block the flusher thread waiting on IO

When sync does it's WB_SYNC_ALL writeback, it issues data Io and
then immediately waits for IO completion. This is done in the
context of the flusher thread, and hence completely ties up the
flusher thread for the backing device until all the dirty inodes
have been synced. On filesystems that are dirtying inodes constantly
and quickly, this means the flusher thread can be tied up for
minutes per sync call and hence badly affect system level write IO
performance as the page cache cannot be cleaned quickly.

We already have a wait loop for IO completion for sync(2), so cut
this out of the flusher thread and delegate it to wait_sb_inodes().
Hence we can do rapid IO submission, and then wait for it all to
complete.

Effect of sync on fsmark before the patch:

FSUse%        Count         Size    Files/sec     App Overhead
.....
     0       640000         4096      35154.6          1026984
     0       720000         4096      36740.3          1023844
     0       800000         4096      36184.6           916599
     0       880000         4096       1282.7          1054367
     0       960000         4096       3951.3           918773
     0      1040000         4096      40646.2           996448
     0      1120000         4096      43610.1           895647
     0      1200000         4096      40333.1           921048

And a single sync pass took:

  real    0m52.407s
  user    0m0.000s
  sys     0m0.090s

After the patch, there is no impact on fsmark results, and each
individual sync(2) operation run concurrently with the same fsmark
workload takes roughly 7s:

  real    0m6.930s
  user    0m0.000s
  sys     0m0.039s

IOWs, sync is 7-8x faster on a busy filesystem and does not have an
adverse impact on ongoing async data write operations.

Signed-off-by: Dave Chinner <dchinner@redhat.com>
Reviewed-by: Jan Kara <jack@suse.cz>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: poondog <markj338@gmail.com>
While Apollyon is fun, let's go back to "daily performance"

Signed-off-by: poondog <markj338@gmail.com>
Mako (absolute) Voltage control.

This started out as just including the existing work of someone else.
But that was so obfuscated and needlessly moved in sysfs, i turned it into the type control
we have on NP, meaning same sysfs location and output formatting.
Since the various kernels range from no preUV to different levels of UV it is best to encourage the user
to think in absolute voltages.
"I can UV -150 on kernel X! Really? Odd, i can only UV kernel Y -50mV!"
Kernel X has no preUV, kernel Y has 100mV preUV, so they both run the same.
This is needlessly confusing to users.

Talking in absolutes, users will get a better understanding of "what the other guy's" device is capable of.
Sticking to a common sysfs location and to the common absolute voltage is thus the right thing to do.

This seems to work now as it should.

This is heavily based on coolbho3k's NP patch. from Paul's stuff we might have a few function names, but not the contents.
This is not his, if he claims otherwise, he is wrong.

Signed-off-by: poondog <markj338@gmail.com>
lower dig and mem voltages, match regulator range tofixed voltage control

Signed-off-by: poondog <markj338@gmail.com>
limiting to 1728 for a stable kernel

Signed-off-by: poondog <markj338@gmail.com>