switch do_fsync() to fget_light()

Signed-off-by: Al Viro <viro@zeniv.linux.org.uk>
Signed-off-by: flar2 <asegaert@gmail.com>
block: Reserve only one queue tag for sync IO if only 3 tags are available

In case a device has three tags available we still reserve two of them
for sync IO. That leaves only a single tag for async IO such as
writeback from flusher thread which results in poor performance.

Allow async IO to consume two tags in case queue has three tag availabe
to get a decent async write performance.

This patch improves streaming write performance on a machine with such disk
from ~21 MB/s to ~52 MB/s. Also postmark throughput in presence of
streaming writer improves from 8 to 12 transactions per second so sync
IO doesn't seem to be harmed in presence of heavy async writer.

Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Jens Axboe <axboe@kernel.dk>
Signed-off-by: Pranav Vashi <neobuddy89@gmail.com>
Signed-off-by: flar2 <asegaert@gmail.com>
readahead: make context readahead more conservative

This helps performance on moderately dense random reads on SSD.

Transaction-Per-Second numbers provided by Taobao:

		QPS	case
		-------------------------------------------------------
		7536	disable context readahead totally
w/ patch:	7129	slower size rampup and start RA on the 3rd read
		6717	slower size rampup
w/o patch:	5581	unmodified context readahead

Before, readahead will be started whenever reading page N+1 when it happen
to read N recently.  After patch, we'll only start readahead when *three*
random reads happen to access pages N, N+1, N+2.  The probability of this
happening is extremely low for pure random reads, unless they are very
dense, which actually deserves some readahead.

Also start with a smaller readahead window.  The impact to interleaved
sequential reads should be small, because for a long run stream, the the
small readahead window rampup phase is negletable.

The context readahead actually benefits clustered random reads on HDD
whose seek cost is pretty high.  However as SSD is increasingly used for
random read workloads it's better for the context readahead to concentrate
on interleaved sequential reads.

Another SSD rand read test from Miao

        # file size:        2GB
        # read IO amount: 625MB
        sysbench --test=fileio          \
                --max-requests=10000    \
                --num-threads=1         \
                --file-num=1            \
                --file-block-size=64K   \
                --file-test-mode=rndrd  \
                --file-fsync-freq=0     \
                --file-fsync-end=off    run

shows the performance of btrfs grows up from 69MB/s to 121MB/s, ext4 from
104MB/s to 121MB/s.

Signed-off-by: Wu Fengguang <fengguang.wu@intel.com>
Tested-by: Tao Ma <tm@tao.ma>
Tested-by: Miao Xie <miaox@cn.fujitsu.com>
Signed-off-by: Andrew Morton <akpm@linux-foundation.org>
Signed-off-by: Linus Torvalds <torvalds@linux-foundation.org>
Signed-off-by: flar2 <asegaert@gmail.com>
nohz: Reduce overhead under high-freq idling patterns

One testbox of mine (Intel Nehalem, 16-way) uses MWAIT for its idle routine,
which apparently can break out of its idle loop rather frequently, with
high frequency.

In that case NO_HZ_FULL=y kernels show high ksoftirqd overhead and constant
context switching, because tick_nohz_stop_sched_tick() will, if
delta_jiffies == 0, mis-identify this as a timer event - activating the
TIMER_SOFTIRQ, which wakes up ksoftirqd.

Fix this by treating delta_jiffies == 0 the same way we treat other short
wakeups, delta_jiffies == 1.

Cc: Frederic Weisbecker <fweisbec@gmail.com>
Cc: Chris Metcalf <cmetcalf@tilera.com>
Cc: Christoph Lameter <cl@linux.com>
Cc: Geoff Levand <geoff@infradead.org>
Cc: Gilad Ben Yossef <gilad@benyossef.com>
Cc: Hakan Akkan <hakanakkan@gmail.com>
Cc: Kevin Hilman <khilman@linaro.org>
Cc: Li Zhong <zhong@linux.vnet.ibm.com>
Cc: Oleg Nesterov <oleg@redhat.com>
Cc: Paul E. McKenney <paulmck@linux.vnet.ibm.com>
Cc: Paul Gortmaker <paul.gortmaker@windriver.com>
Cc: Peter Zijlstra <peterz@infradead.org>
Cc: Steven Rostedt <rostedt@goodmis.org>
Signed-off-by: Ingo Molnar <mingo@kernel.org>
Signed-off-by: franciscofranco <franciscofranco.1990@gmail.com>
Signed-off-by: flar2 <asegaert@gmail.com>
softirq: reduce latencies

In various network workloads, __do_softirq() latencies can be up
to 20 ms if HZ=1000, and 200 ms if HZ=100.

This is because we iterate 10 times in the softirq dispatcher,
and some actions can consume a lot of cycles.

This patch changes the fallback to ksoftirqd condition to :

- A time limit of 2 ms.
- need_resched() being set on current task

When one of this condition is met, we wakeup ksoftirqd for further
softirq processing if we still have pending softirqs.

Using need_resched() as the only condition can trigger RCU stalls,
as we can keep BH disabled for too long.

I ran several benchmarks and got no significant difference in
throughput, but a very significant reduction of latencies (one order
of magnitude) :

In following bench, 200 antagonist "netperf -t TCP_RR" are started in
background, using all available cpus.

Then we start one "netperf -t TCP_RR", bound to the cpu handling the NIC
IRQ (hard+soft)

Before patch :

# netperf -H 7.7.7.84 -t TCP_RR -T2,2 -- -k
RT_LATENCY,MIN_LATENCY,MAX_LATENCY,P50_LATENCY,P90_LATENCY,P99_LATENCY,MEAN_LATENCY,STDDEV_LATENCY
MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET
to 7.7.7.84 () port 0 AF_INET : first burst 0 : cpu bind
RT_LATENCY=550110.424
MIN_LATENCY=146858
MAX_LATENCY=997109
P50_LATENCY=305000
P90_LATENCY=550000
P99_LATENCY=710000
MEAN_LATENCY=376989.12
STDDEV_LATENCY=184046.92

After patch :

# netperf -H 7.7.7.84 -t TCP_RR -T2,2 -- -k
RT_LATENCY,MIN_LATENCY,MAX_LATENCY,P50_LATENCY,P90_LATENCY,P99_LATENCY,MEAN_LATENCY,STDDEV_LATENCY
MIGRATED TCP REQUEST/RESPONSE TEST from 0.0.0.0 (0.0.0.0) port 0 AF_INET
to 7.7.7.84 () port 0 AF_INET : first burst 0 : cpu bind
RT_LATENCY=40545.492
MIN_LATENCY=9834
MAX_LATENCY=78366
P50_LATENCY=33583
P90_LATENCY=59000
P99_LATENCY=69000
MEAN_LATENCY=38364.67
STDDEV_LATENCY=12865.26

Signed-off-by: Eric Dumazet <edumazet@google.com>
Cc: David Miller <davem@davemloft.net>
Cc: Tom Herbert <therbert@google.com>
Cc: Ben Hutchings <bhutchings@solarflare.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
Signed-off-by: flar2 <asegaert@gmail.com>
writeback: Fix occasional slow sync(1)

In case when system contains no dirty pages, wakeup_flusher_threads()
will submit WB_SYNC_NONE writeback for 0 pages so wb_writeback() exits
immediately without doing anything. Thus sync(1) will write all the
dirty inodes from a WB_SYNC_ALL writeback pass which is slow.

Fix the problem by using get_nr_dirty_pages() in
wakeup_flusher_threads() instead of calculating number of dirty pages
manually. That function also takes number of dirty inodes into account.

CC: stable@vger.kernel.org
Reported-by: Paul Taysom <taysom@chromium.org>
Signed-off-by: Jan Kara <jack@suse.cz>
Signed-off-by: Cristoforo Cataldo <cristoforo.cataldo@gmail.com>
Signed-off-by: Francisco Franco <franciscofranco.1990@gmail.com>
Signed-off-by: flar2 <asegaert@gmail.com>
block: row: Remove warning massage from add_request

Regular priority queues is marked as "starved" if it skipped a dispatch
due to being empty. When a new request is added to a "starved" queue
it will be marked as urgent.
The removed WARN_ON was warning about an impossible case when a regular
priority (read) queue was marked as starved but wasn't empty. This is
a possible case due to the bellow:
If the device driver fetched a read request that is pending for
transmission and an URGENT request arrives, the fetched read will be
reinserted back to the scheduler. Its possible that the queue it will be
reinserted to was marked as "starved" in the meanwhile due to being empty.

CRs-fixed: 517800
Change-Id: Iaae642ea0ed9c817c41745b0e8ae2217cc684f0c
Signed-off-by: Tatyana Brokhman <tlinder@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
mmc: core: Refactor bus speed selection code

The bus speed selection code in mmc_card_init() is convoluted, refactor
the code to simplify this and make it simpler for adding new bus speed
capabilities.

Signed-off-by: Venkat Gopalakrishnan <venkatg@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
mmc: card: update long_sequential_write_test queue depth

Since some systems have higher memory pressure, we limit the amount of
simultaneous test requests. The former limitation was 118, due to the
request queue size, but now we further restrict this number to half.

Change-Id: I893b9ad1b133c922f90497b0ec1f416514529fb8
CRs-fixed: 510814
Signed-off-by: Lee Susman <lsusman@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
mmc: print an error on FLUSH timeout

Up until now the FLUSH timeout error was not printed and there
was no way to know if the FLUSH completed successfully or not.
Printing the FLUSH failure will help to identify if FS corruption
happened due to this timeout.

Change-Id: Ibbb51d030d7130d63974a1b4319ad4a24621c595
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
mmc: block: flush request requeue after timeout.

On some eMMC cards cache flush is taking longer than 30 sec timeout
after HPI issued and -EIO reported to the upper layers. This may result
into journaling issues as flush calls are issued by the file system
joulrnaling code.

This change increases flash cache timeout to 90 sec, in case of timeout
occurs, after HPI issued, flash request re-queued to the block layer queue
to execute it later and keep journaling logic valid.

Conflicts:
	drivers/mmc/card/block.c

Change-Id: I1e968c07056062fd9c8e14e5bc3e62b3b4b99c64
Signed-off-by: Panwar Vivek <vpanwa@codeaurora.org>

Conflicts:

	drivers/mmc/card/block.c

Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
sdhci: sdhci_stop_request() returns error when no request

There is race between sdhci_tasklet_finish()
and sdhci_stop_request(): when the request is finished before
stop flow called, error returned.

Change-Id: Ic036feae925b2e9e5435e44f97b24a179547bf49
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
mmc: core: skip stop flow when current request already done

When mmc_stop_request() has no request to stop, because underlying
host driver reported this, the flow should wait for the mmc done()
callback marking that urgent still pending.

Change-Id: Iacc95591ee76a965916af05a31a67dd8997c233e
CRs-Fixed: 538117
Signed-off-by: Konstantin Dorfman <kdorfman@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
mmc: block: Fix error path of mmc_blk_alloc_req()

In case of any error within mmc_blk_alloc_req(), the bitmaps
that keep track of devices are not getting cleared. This may
result in failure to detect a card in case it reaches maximum
devices limitation. Fix it by clearing those bitmaps appropriately.

CRs-fixed: 563264
Change-Id: I0e23c45856355565534146f5fabb957fd4b1d007
Signed-off-by: Sahitya Tummala <stummala@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
mmc: sdhci: Use max timeout and skip timeout calculation

Several data-timeout issues were seen, most of which were
due to the card taking a longer time to respond. This patch
increases the timeout of the controller to 0xF i.e. max
possible.

Change-Id: I6739de3eb5d9cccf8e39d9dc4730056782334162
CRs-Fixed: 536832
Signed-off-by: Asutosh Das <asutoshd@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
mmc: core: increase timeout for disable cache operation

According to eMMC specification, there is no upper bound defined on
a flush request and the duration of flush operation is left to card
vendor's implementation. This means that it may take a very long
time to complete.

When eMMC cache is disabled, the card has to flush all the data in its
cache. So this means that for certain cards, the driver is not waiting
long enough for the flush to complete during cache disable operation,
leading to data on the card being corrupted.

This change increases the timeout for cache disable operation, thus
preventing data corruption.

CRs-Fixed: 562350
Change-Id: If68328ab56b50c7596800f07ef92c0ab16a55ec0
Signed-off-by: Maya Erez <merez@codeaurora.org>
Signed-off-by: David Ng <dave@codeaurora.org>
Signed-off-by: Krishna Konda <kkonda@codeaurora.org>
Signed-off-by: flar2 <asegaert@gmail.com>
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