writeback: fix writeback cache thrashing

From: Namjae Jeon <namjae.jeon@samsung.com>

Consider Process A: huge I/O on sda
        doing heavy write operation - dirty memory becomes more
        than dirty_background_ratio
        on HDD - flusher thread flush-8:0

Consider Process B: small I/O on sdb
        doing while [1]; read 1024K + rewrite 1024K + sleep 2sec
        on Flash device - flusher thread flush-8:16

As Process A is a heavy dirtier, dirty memory becomes more
than dirty_background_thresh. Due to this, below check becomes
true(checking global_page_state in over_bground_thresh)
for all bdi devices(even for very small dirtied bdi - sdb):

In this case, even small cached data on 'sdb' is forced to flush
and writeback cache thrashing happens.

When we added debug prints inside above 'if' condition and ran
above Process A(heavy dirtier on bdi with flush-8:0) and
Process B(1024K frequent read/rewrite on bdi with flush-8:16)
we got below prints:

[Test setup: ARM dual core CPU, 512 MB RAM]

[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  56064 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  56704 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 84720 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 94720 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   384 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   960 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =    64 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 92160 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   256 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   768 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =    64 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   256 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   320 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =     0 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 92032 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 91968 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   192 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =  1024 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =    64 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   192 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   576 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =     0 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 84352 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   192 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =   512 KB
[over_bground_thresh]: wakeup flush-8:16 : BDI_RECLAIMABLE =     0 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 92608 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE = 92544 KB

As mentioned in above log, when global dirty memory > global background_thresh
small cached data is also forced to flush by flush-8:16.
If removing global background_thresh checking code, we can reduce cache
thrashing of frequently used small data.
And It will be great if we can reserve a portion of writeback cache using
min_ratio.

After applying patch:
$ echo 5 > /sys/block/sdb/bdi/min_ratio
$ cat /sys/block/sdb/bdi/min_ratio
5
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  56064 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  56704 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  84160 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  96960 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  94080 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  93120 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  93120 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  91520 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  89600 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  93696 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  93696 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  72960 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  90624 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  90624 KB
[over_bground_thresh]: wakeup flush-8:0 : BDI_RECLAIMABLE =  90688 KB

As mentioned in the above logs, once cache is reserved for Process B,
and patch is applied there is less writeback cache thrashing on sdb
by frequent forced writeback by flush-8:16 in over_bground_thresh.

After all, small cached data will be flushed by periodic writeback
once every dirty_writeback_interval.

Suggested-by: Wanpeng Li <liwanp@linux.vnet.ibm.com>
Signed-off-by: Namjae Jeon <namjae.jeon@samsung.com>
Signed-off-by: Vivek Trivedi <t.vivek@samsung.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
writeback: increase bdi_min_ratio to 5 in light of the latest writeback commit.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
writeback: I believe these defines were calculated with HZ=1000 in mind. Since our devices are HZ=100 I hardcoded the values on this constants. I'm not 100% sure if this code was made for HZ with 1000 but I couldn't track it to understand clearly. Although I didn't see any drawback of using this as it is now. If anyone knows the answer please chime in.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
CHROMIUM: tcp: Avoid merging segments on the OOO queue into a cloned SKB

TCP tries to merge socket buffers in the out-of-order queue when they
are sequential. This is generally a good thing to save memory and speed
up processing, but can lead to problems when it expands a buffer that
has previously been cloned.

We have encountered a bug with a confused/broken receive queue, that we
think might have been caused by this problem, as the smsc95xx driver
uses cloned buffers in its receive path. Thanks to edumazet for
pointing that out and suggesting this fix.

This patch makes sure that this code path only expands socket buffers
that have not been cloned and just enqueues them normally in the other
case. In upstream kernels starting with 3.5, the affected code has been
refactored into tcp_try_coalesce with commit 1402d36, which has later
been patched to fix this issue in commit 923dd34. The fix has not been
backported into the upstream 3.4 kernel.

BUG=chromium-os:35827
TEST=None

Change-Id: I2cdf09946a3cbb0cbff35b1ac09313352b8f1e94
Signed-off-by: Julius Werner <jwerner@chromium.org>
Reviewed-on: https://gerrit.chromium.org/gerrit/37666
Reviewed-by: Eric Dumazet <edumazet@chromium.org>
Reviewed-by: Sameer Nanda <snanda@chromium.org>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
cpuidle: move field disable from per-driver to per-cpu

Andrew J.Schorr raises a question.  When he changes the disable setting on
a single CPU, it affects all the other CPUs.  Basically, currently, the
disable field is per-driver instead of per-cpu.  All the C states of the
same driver are shared by all CPU in the same machine.

The patch changes the `disable' field to per-cpu, so we could set this
separately for each cpu.

Signed-off-by: ShuoX Liu <shuox.liu@intel.com>
Reported-by: Andrew J.Schorr <aschorr@telemetry-investments.com>
Reviewed-by: Yanmin Zhang <yanmin_zhang@intel.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Rafael J. Wysocki <rjw@sisk.pl>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
cpuidle: Quickly notice prediction failure for repeat mode

The prediction for future is difficult and when the cpuidle governor prediction
fails and govenor possibly choose the shallower C-state than it should. How to
quickly notice and find the failure becomes important for power saving.

cpuidle menu governor has a method to predict the repeat pattern if there are 8
C-states residency which are continuous and the same or very close, so it will
predict the next C-states residency will keep same residency time.

There is a real case that turbostat utility (tools/power/x86/turbostat)
at kernel 3.3 or early. turbostat utility will read 10 registers one by one at
Sandybridge, so it will generate 10 IPIs to wake up idle CPUs. So cpuidle menu
 governor will predict it is repeat mode and there is another IPI wake up idle
 CPU soon, so it keeps idle CPU stay at C1 state even though CPU is totally
idle. However, in the turbostat, following 10 registers reading is sleep 5
seconds by default, so the idle CPU will keep at C1 for a long time though it is
 idle until break event occurs.
In a idle Sandybridge system, run "./turbostat -v", we will notice that deep
C-state dangles between "70% ~ 99%". After patched the kernel, we will notice
deep C-state stays at >99.98%.

In the patch, a timer is added when menu governor detects a repeat mode and
choose a shallow C-state. The timer is set to a time out value that greater
than predicted time, and we conclude repeat mode prediction failure if timer is
triggered. When repeat mode happens as expected, the timer is not triggered
and CPU waken up from C-states and it will cancel the timer initiatively.
When repeat mode does not happen, the timer will be time out and menu governor
will quickly notice that the repeat mode prediction fails and then re-evaluates
deeper C-states possibility.

Below is another case which will clearly show the patch much benefit:

volatile int * shutdown;
volatile long * count;
int delay = 20;
int loop = 8;

void usage(void)
{
	fprintf(stderr,
		"Usage: idle_predict [options]\n"
		"  --help	-h  Print this help\n"
		"  --thread	-n  Thread number\n"
		"  --loop     	-l  Loop times in shallow Cstate\n"
		"  --delay	-t  Sleep time (uS)in shallow Cstate\n");
}

void *simple_loop() {
	int idle_num = 1;
	while (!(*shutdown)) {
		*count = *count + 1;

		if (idle_num % loop)
			usleep(delay);
		else {
			/* sleep 1 second */
			usleep(1000000);
			idle_num = 0;
		}
		idle_num++;
	}

}

static void sighand(int sig)
{
	*shutdown = 1;
}

int main(int argc, char *argv[])
{
	sigset_t sigset;
	int signum = SIGALRM;
	int i, c, er = 0, thread_num = 8;
	pthread_t pt[1024];

	static char optstr[] = "n:l:t:h:";

	while ((c = getopt(argc, argv, optstr)) != EOF)
		switch (c) {
			case 'n':
				thread_num = atoi(optarg);
				break;
			case 'l':
				loop = atoi(optarg);
				break;
			case 't':
				delay = atoi(optarg);
				break;
			case 'h':
			default:
				usage();
				exit(1);
		}

	printf("thread=%d,loop=%d,delay=%d\n",thread_num,loop,delay);
	count = malloc(sizeof(long));
	shutdown = malloc(sizeof(int));
	*count = 0;
	*shutdown = 0;

	sigemptyset(&sigset);
	sigaddset(&sigset, signum);
	sigprocmask (SIG_BLOCK, &sigset, NULL);
	signal(SIGINT, sighand);
	signal(SIGTERM, sighand);

	for(i = 0; i < thread_num ; i++)
		pthread_create(&pt[i], NULL, simple_loop, NULL);

	for (i = 0; i < thread_num; i++)
		pthread_join(pt[i], NULL);

	exit(0);
}

Get powertop V2 from git://github.com/fenrus75/powertop, build powertop.
After build the above test application, then run it.
Test plaform can be Intel Sandybridge or other recent platforms.

We will find that deep C-state will dangle between 40%~100% and much time spent
on C1 state. It is because menu governor wrongly predict that repeat mode
is kept, so it will choose the C1 shallow C-state even though it has chance to
sleep 1 second in deep C-state.

While after patched the kernel, we find that deep C-state will keep >99.6%.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>

Conflicts:

	kernel/time/tick-sched.c

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
cpuidle: Quickly notice prediction failure in general case

The prediction for future is difficult and when the cpuidle governor prediction
fails and govenor possibly choose the shallower C-state than it should. How to
quickly notice and find the failure becomes important for power saving.

The patch extends to general case that prediction logic get a small predicted
residency, so it choose a shallow C-state though the expected residency is large
. Once the prediction will be fail, the CPU will keep staying at shallow C-state
for a long time. Acutally, the CPU has change enter into deep C-state.
So when the expected residency is long enough but governor choose a shallow
C-state, an timer will be added in order to monitor if the prediction failure.

When C-state is waken up prior to the adding timer, the timer will be cancelled
initiatively. When the timer is triggered and menu governor will quickly notice
prediction failure and re-evaluates deeper C-states possibility.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
cpuidle: Get typical recent sleep interval

The function detect_repeating_patterns was not very useful for
workloads with alternating long and short pauses, for example
virtual machines handling network requests for each other (say
a web and database server).

Instead, try to find a recent sleep interval that is somewhere
between the median and the mode sleep time, by discarding outliers
to the up side and recalculating the average and standard deviation
until that is no longer required.

This should do something sane with a sleep interval series like:

	200 180 210 10000 30 1000 170 200

The current code would simply discard such a series, while the
new code will guess a typical sleep interval just shy of 200.

The original patch come from Rik van Riel <riel@redhat.com>.

Signed-off-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Youquan Song <youquan.song@intel.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
cpuidle: Fix finding state with min power_usage

Since cpuidle_state.power_usage is a signed value, use INT_MAX (instead
of -1) to init the local copies so that functions that tries to find
cpuidle states with minimum power usage works correctly even if they use
non-negative values.

Signed-off-by: Sivaram Nair <sivaramn@nvidia.com>
Reviewed-by: Rik van Riel <riel@redhat.com>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
cpuidle: remove the power_specified field in the driver

We realized that the power usage field is never filled and when it
is filled for tegra, the power_specified flag is not set causing all
of these values to be reset when the driver is initialized with
set_power_state().

However, the power_specified flag can be simply removed under the
assumption that the states are always backward sorted, which is the
case with the current code.

This change allows the menu governor select function and the
cpuidle_play_dead() to be simplified.  Moreover, the
set_power_states() function can removed as it does not make sense
any more.

Drop the power_specified flag from struct cpuidle_driver and make
the related changes as described above.

As a consequence, this also fixes the bug where on the dynamic
C-states system, the power fields are not initialized.

[rjw: Changelog]
References: https://bugzilla.kernel.org/show_bug.cgi?id=42870
References: https://bugzilla.kernel.org/show_bug.cgi?id=43349
References: https://lkml.org/lkml/2012/10/16/518
Signed-off-by: Daniel Lezcano <daniel.lezcano@linaro.org>
Signed-off-by: Rafael J. Wysocki <rafael.j.wysocki@intel.com>

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>

Conflicts:

	drivers/cpuidle/cpuidle.c
	drivers/cpuidle/driver.c

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
cpufreq: ondemand: improve input_boost_freq logic in case users prefer to use ondemand.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
config: Remove unused MEDIA_TUNER option

Signed-off-by: Stratos Karafotis <stratosk@semaphore.gr>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
This is definitely not needed for Mako.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
video: msm_fb: reduce logging level.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
cpufreq: interactive: no need to block cpu0 frequency if its >= input_boost_freq. If we don't need to run it higher than input_boost_freq then the next freq will be input_boost_freq. This should save some battery in the long run. Thanks reborn90.

Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>