<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/drivers/block, branch v3.17-rc2</title>
<subtitle>Linux kernel for Apalis and Colibri modules</subtitle>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/'/>
<entry>
<title>Merge tag 'pci-v3.17-changes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci</title>
<updated>2014-08-15T00:10:33+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2014-08-15T00:10:33+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=a11c5c9ef6dc562fc7df7aaf7911569a85f4d71c'/>
<id>a11c5c9ef6dc562fc7df7aaf7911569a85f4d71c</id>
<content type='text'>
Pull DEFINE_PCI_DEVICE_TABLE removal from Bjorn Helgaas:
 "Part two of the PCI changes for v3.17:

    - Remove DEFINE_PCI_DEVICE_TABLE macro use (Benoit Taine)

  It's a mechanical change that removes uses of the
  DEFINE_PCI_DEVICE_TABLE macro.  I waited until later in the merge
  window to reduce conflicts, but it's possible you'll still see a few"

* tag 'pci-v3.17-changes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci:
  PCI: Remove DEFINE_PCI_DEVICE_TABLE macro use
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull DEFINE_PCI_DEVICE_TABLE removal from Bjorn Helgaas:
 "Part two of the PCI changes for v3.17:

    - Remove DEFINE_PCI_DEVICE_TABLE macro use (Benoit Taine)

  It's a mechanical change that removes uses of the
  DEFINE_PCI_DEVICE_TABLE macro.  I waited until later in the merge
  window to reduce conflicts, but it's possible you'll still see a few"

* tag 'pci-v3.17-changes-2' of git://git.kernel.org/pub/scm/linux/kernel/git/helgaas/pci:
  PCI: Remove DEFINE_PCI_DEVICE_TABLE macro use
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'for-3.17/drivers' of git://git.kernel.dk/linux-block</title>
<updated>2014-08-14T15:10:21+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2014-08-14T15:10:21+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=d429a3639ca967ce2f35e3e8d4e70caec7149ded'/>
<id>d429a3639ca967ce2f35e3e8d4e70caec7149ded</id>
<content type='text'>
Pull block driver changes from Jens Axboe:
 "Nothing out of the ordinary here, this pull request contains:

   - A big round of fixes for bcache from Kent Overstreet, Slava Pestov,
     and Surbhi Palande.  No new features, just a lot of fixes.

   - The usual round of drbd updates from Andreas Gruenbacher, Lars
     Ellenberg, and Philipp Reisner.

   - virtio_blk was converted to blk-mq back in 3.13, but now Ming Lei
     has taken it one step further and added support for actually using
     more than one queue.

   - Addition of an explicit SG_FLAG_Q_AT_HEAD for block/bsg, to
     compliment the the default behavior of adding to the tail of the
     queue.  From Douglas Gilbert"

* 'for-3.17/drivers' of git://git.kernel.dk/linux-block: (86 commits)
  bcache: Drop unneeded blk_sync_queue() calls
  bcache: add mutex lock for bch_is_open
  bcache: Correct printing of btree_gc_max_duration_ms
  bcache: try to set b-&gt;parent properly
  bcache: fix memory corruption in init error path
  bcache: fix crash with incomplete cache set
  bcache: Fix more early shutdown bugs
  bcache: fix use-after-free in btree_gc_coalesce()
  bcache: Fix an infinite loop in journal replay
  bcache: fix crash in bcache_btree_node_alloc_fail tracepoint
  bcache: bcache_write tracepoint was crashing
  bcache: fix typo in bch_bkey_equal_header
  bcache: Allocate bounce buffers with GFP_NOWAIT
  bcache: Make sure to pass GFP_WAIT to mempool_alloc()
  bcache: fix uninterruptible sleep in writeback thread
  bcache: wait for buckets when allocating new btree root
  bcache: fix crash on shutdown in passthrough mode
  bcache: fix lockdep warnings on shutdown
  bcache allocator: send discards with correct size
  bcache: Fix to remove the rcu_sched stalls.
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull block driver changes from Jens Axboe:
 "Nothing out of the ordinary here, this pull request contains:

   - A big round of fixes for bcache from Kent Overstreet, Slava Pestov,
     and Surbhi Palande.  No new features, just a lot of fixes.

   - The usual round of drbd updates from Andreas Gruenbacher, Lars
     Ellenberg, and Philipp Reisner.

   - virtio_blk was converted to blk-mq back in 3.13, but now Ming Lei
     has taken it one step further and added support for actually using
     more than one queue.

   - Addition of an explicit SG_FLAG_Q_AT_HEAD for block/bsg, to
     compliment the the default behavior of adding to the tail of the
     queue.  From Douglas Gilbert"

* 'for-3.17/drivers' of git://git.kernel.dk/linux-block: (86 commits)
  bcache: Drop unneeded blk_sync_queue() calls
  bcache: add mutex lock for bch_is_open
  bcache: Correct printing of btree_gc_max_duration_ms
  bcache: try to set b-&gt;parent properly
  bcache: fix memory corruption in init error path
  bcache: fix crash with incomplete cache set
  bcache: Fix more early shutdown bugs
  bcache: fix use-after-free in btree_gc_coalesce()
  bcache: Fix an infinite loop in journal replay
  bcache: fix crash in bcache_btree_node_alloc_fail tracepoint
  bcache: bcache_write tracepoint was crashing
  bcache: fix typo in bch_bkey_equal_header
  bcache: Allocate bounce buffers with GFP_NOWAIT
  bcache: Make sure to pass GFP_WAIT to mempool_alloc()
  bcache: fix uninterruptible sleep in writeback thread
  bcache: wait for buckets when allocating new btree root
  bcache: fix crash on shutdown in passthrough mode
  bcache: fix lockdep warnings on shutdown
  bcache allocator: send discards with correct size
  bcache: Fix to remove the rcu_sched stalls.
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>Merge branch 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client</title>
<updated>2014-08-13T23:43:29+00:00</updated>
<author>
<name>Linus Torvalds</name>
<email>torvalds@linux-foundation.org</email>
</author>
<published>2014-08-13T23:43:29+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=8d2d441ac4af223eae466c3c31ff737cc31a1411'/>
<id>8d2d441ac4af223eae466c3c31ff737cc31a1411</id>
<content type='text'>
Pull Ceph updates from Sage Weil:
 "There is a lot of refactoring and hardening of the libceph and rbd
  code here from Ilya that fix various smaller bugs, and a few more
  important fixes with clone overlap.  The main fix is a critical change
  to the request_fn handling to not sleep that was exposed by the recent
  mutex changes (which will also go to the 3.16 stable series).

  Yan Zheng has several fixes in here for CephFS fixing ACL handling,
  time stamps, and request resends when the MDS restarts.

  Finally, there are a few cleanups from Himangi Saraogi based on
  Coccinelle"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (39 commits)
  libceph: set last_piece in ceph_msg_data_pages_cursor_init() correctly
  rbd: remove extra newlines from rbd_warn() messages
  rbd: allocate img_request with GFP_NOIO instead GFP_ATOMIC
  rbd: rework rbd_request_fn()
  ceph: fix kick_requests()
  ceph: fix append mode write
  ceph: fix sizeof(struct tYpO *) typo
  ceph: remove redundant memset(0)
  rbd: take snap_id into account when reading in parent info
  rbd: do not read in parent info before snap context
  rbd: update mapping size only on refresh
  rbd: harden rbd_dev_refresh() and callers a bit
  rbd: split rbd_dev_spec_update() into two functions
  rbd: remove unnecessary asserts in rbd_dev_image_probe()
  rbd: introduce rbd_dev_header_info()
  rbd: show the entire chain of parent images
  ceph: replace comma with a semicolon
  rbd: use rbd_segment_name_free() instead of kfree()
  ceph: check zero length in ceph_sync_read()
  ceph: reset r_resend_mds after receiving -ESTALE
  ...
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Pull Ceph updates from Sage Weil:
 "There is a lot of refactoring and hardening of the libceph and rbd
  code here from Ilya that fix various smaller bugs, and a few more
  important fixes with clone overlap.  The main fix is a critical change
  to the request_fn handling to not sleep that was exposed by the recent
  mutex changes (which will also go to the 3.16 stable series).

  Yan Zheng has several fixes in here for CephFS fixing ACL handling,
  time stamps, and request resends when the MDS restarts.

  Finally, there are a few cleanups from Himangi Saraogi based on
  Coccinelle"

* 'for-linus' of git://git.kernel.org/pub/scm/linux/kernel/git/sage/ceph-client: (39 commits)
  libceph: set last_piece in ceph_msg_data_pages_cursor_init() correctly
  rbd: remove extra newlines from rbd_warn() messages
  rbd: allocate img_request with GFP_NOIO instead GFP_ATOMIC
  rbd: rework rbd_request_fn()
  ceph: fix kick_requests()
  ceph: fix append mode write
  ceph: fix sizeof(struct tYpO *) typo
  ceph: remove redundant memset(0)
  rbd: take snap_id into account when reading in parent info
  rbd: do not read in parent info before snap context
  rbd: update mapping size only on refresh
  rbd: harden rbd_dev_refresh() and callers a bit
  rbd: split rbd_dev_spec_update() into two functions
  rbd: remove unnecessary asserts in rbd_dev_image_probe()
  rbd: introduce rbd_dev_header_info()
  rbd: show the entire chain of parent images
  ceph: replace comma with a semicolon
  rbd: use rbd_segment_name_free() instead of kfree()
  ceph: check zero length in ceph_sync_read()
  ceph: reset r_resend_mds after receiving -ESTALE
  ...
</pre>
</div>
</content>
</entry>
<entry>
<title>PCI: Remove DEFINE_PCI_DEVICE_TABLE macro use</title>
<updated>2014-08-12T18:15:14+00:00</updated>
<author>
<name>Benoit Taine</name>
<email>benoit.taine@lip6.fr</email>
</author>
<published>2014-08-08T13:56:03+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=9baa3c34ac4e27f7e062f266f50cc5dbea26a6c1'/>
<id>9baa3c34ac4e27f7e062f266f50cc5dbea26a6c1</id>
<content type='text'>
We should prefer `struct pci_device_id` over `DEFINE_PCI_DEVICE_TABLE` to
meet kernel coding style guidelines.  This issue was reported by checkpatch.

A simplified version of the semantic patch that makes this change is as
follows (http://coccinelle.lip6.fr/):

// &lt;smpl&gt;

@@
identifier i;
declarer name DEFINE_PCI_DEVICE_TABLE;
initializer z;
@@

- DEFINE_PCI_DEVICE_TABLE(i)
+ const struct pci_device_id i[]
= z;

// &lt;/smpl&gt;

[bhelgaas: add semantic patch]
Signed-off-by: Benoit Taine &lt;benoit.taine@lip6.fr&gt;
Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
We should prefer `struct pci_device_id` over `DEFINE_PCI_DEVICE_TABLE` to
meet kernel coding style guidelines.  This issue was reported by checkpatch.

A simplified version of the semantic patch that makes this change is as
follows (http://coccinelle.lip6.fr/):

// &lt;smpl&gt;

@@
identifier i;
declarer name DEFINE_PCI_DEVICE_TABLE;
initializer z;
@@

- DEFINE_PCI_DEVICE_TABLE(i)
+ const struct pci_device_id i[]
= z;

// &lt;/smpl&gt;

[bhelgaas: add semantic patch]
Signed-off-by: Benoit Taine &lt;benoit.taine@lip6.fr&gt;
Signed-off-by: Bjorn Helgaas &lt;bhelgaas@google.com&gt;</pre>
</div>
</content>
</entry>
<entry>
<title>block: use pci_zalloc_consistent</title>
<updated>2014-08-08T22:57:28+00:00</updated>
<author>
<name>Joe Perches</name>
<email>joe@perches.com</email>
</author>
<published>2014-08-08T21:24:12+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=a5bbf6160c2b5ebce1533bf989c7cd0086beeabf'/>
<id>a5bbf6160c2b5ebce1533bf989c7cd0086beeabf</id>
<content type='text'>
Remove the now unnecessary memset too.

Signed-off-by: Joe Perches &lt;joe@perches.com&gt;
Mike Miller &lt;mike.miller@hp.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Remove the now unnecessary memset too.

Signed-off-by: Joe Perches &lt;joe@perches.com&gt;
Mike Miller &lt;mike.miller@hp.com&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>rbd: remove extra newlines from rbd_warn() messages</title>
<updated>2014-08-07T12:01:09+00:00</updated>
<author>
<name>Ilya Dryomov</name>
<email>ilya.dryomov@inktank.com</email>
</author>
<published>2014-07-11T08:11:20+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=9584d5082653429ea219f9739a08566478b39f16'/>
<id>9584d5082653429ea219f9739a08566478b39f16</id>
<content type='text'>
rbd_warn() string should be a single line - rbd_warn() appends \n.

Signed-off-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
rbd_warn() string should be a single line - rbd_warn() appends \n.

Signed-off-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>rbd: allocate img_request with GFP_NOIO instead GFP_ATOMIC</title>
<updated>2014-08-07T12:00:52+00:00</updated>
<author>
<name>Ilya Dryomov</name>
<email>ilya.dryomov@inktank.com</email>
</author>
<published>2014-08-05T07:25:54+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=7a716aac01eedb8a7ebf36a0e81237c56f9f1bc1'/>
<id>7a716aac01eedb8a7ebf36a0e81237c56f9f1bc1</id>
<content type='text'>
Now that rbd_img_request_create() is called from work functions, no
need to use GFP_ATOMIC.

Signed-off-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
Reviewed-by: Alex Elder &lt;elder@linaro.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Now that rbd_img_request_create() is called from work functions, no
need to use GFP_ATOMIC.

Signed-off-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
Reviewed-by: Alex Elder &lt;elder@linaro.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>rbd: rework rbd_request_fn()</title>
<updated>2014-08-07T10:56:20+00:00</updated>
<author>
<name>Ilya Dryomov</name>
<email>ilya.dryomov@inktank.com</email>
</author>
<published>2014-08-04T14:04:39+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=bc1ecc65a259fa9333dc8bd6a4ba0cf03b7d4bf8'/>
<id>bc1ecc65a259fa9333dc8bd6a4ba0cf03b7d4bf8</id>
<content type='text'>
While it was never a good idea to sleep in request_fn(), commit
34c6bc2c919a ("locking/mutexes: Add extra reschedule point") made it
a *bad* idea.  mutex_lock() since 3.15 may reschedule *before* putting
task on the mutex wait queue, which for tasks in !TASK_RUNNING state
means block forever.  request_fn() may be called with !TASK_RUNNING on
the way to schedule() in io_schedule().

Offload request handling to a workqueue, one per rbd device, to avoid
calling blocking primitives from rbd_request_fn().

Fixes: http://tracker.ceph.com/issues/8818

Cc: stable@vger.kernel.org # 3.16, needs backporting for 3.15
Signed-off-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
Tested-by: Eric Eastman &lt;eric0e@aol.com&gt;
Tested-by: Greg Wilson &lt;greg.wilson@keepertech.com&gt;
Reviewed-by: Alex Elder &lt;elder@linaro.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
While it was never a good idea to sleep in request_fn(), commit
34c6bc2c919a ("locking/mutexes: Add extra reschedule point") made it
a *bad* idea.  mutex_lock() since 3.15 may reschedule *before* putting
task on the mutex wait queue, which for tasks in !TASK_RUNNING state
means block forever.  request_fn() may be called with !TASK_RUNNING on
the way to schedule() in io_schedule().

Offload request handling to a workqueue, one per rbd device, to avoid
calling blocking primitives from rbd_request_fn().

Fixes: http://tracker.ceph.com/issues/8818

Cc: stable@vger.kernel.org # 3.16, needs backporting for 3.15
Signed-off-by: Ilya Dryomov &lt;ilya.dryomov@inktank.com&gt;
Tested-by: Eric Eastman &lt;eric0e@aol.com&gt;
Tested-by: Greg Wilson &lt;greg.wilson@keepertech.com&gt;
Reviewed-by: Alex Elder &lt;elder@linaro.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>zram: replace global tb_lock with fine grain lock</title>
<updated>2014-08-07T01:01:23+00:00</updated>
<author>
<name>Weijie Yang</name>
<email>weijie.yang@samsung.com</email>
</author>
<published>2014-08-06T23:08:31+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=d2d5e762c8990c4031890e03565983a05febd64a'/>
<id>d2d5e762c8990c4031890e03565983a05febd64a</id>
<content type='text'>
Currently, we use a rwlock tb_lock to protect concurrent access to the
whole zram meta table.  However, according to the actual access model,
there is only a small chance for upper user to access the same
table[index], so the current lock granularity is too big.

The idea of optimization is to change the lock granularity from whole
meta table to per table entry (table -&gt; table[index]), so that we can
protect concurrent access to the same table[index], meanwhile allow the
maximum concurrency.

With this in mind, several kinds of locks which could be used as a
per-entry lock were tested and compared:

Test environment:
x86-64 Intel Core2 Q8400, system memory 4GB, Ubuntu 12.04,
kernel v3.15.0-rc3 as base, zram with 4 max_comp_streams LZO.

iozone test:
iozone -t 4 -R -r 16K -s 200M -I +Z
(1GB zram with ext4 filesystem, take the average of 10 tests, KB/s)

      Test       base      CAS    spinlock    rwlock   bit_spinlock
-------------------------------------------------------------------
 Initial write  1381094   1425435   1422860   1423075   1421521
       Rewrite  1529479   1641199   1668762   1672855   1654910
          Read  8468009  11324979  11305569  11117273  10997202
       Re-read  8467476  11260914  11248059  11145336  10906486
  Reverse Read  6821393   8106334   8282174   8279195   8109186
   Stride read  7191093   8994306   9153982   8961224   9004434
   Random read  7156353   8957932   9167098   8980465   8940476
Mixed workload  4172747   5680814   5927825   5489578   5972253
  Random write  1483044   1605588   1594329   1600453   1596010
        Pwrite  1276644   1303108   1311612   1314228   1300960
         Pread  4324337   4632869   4618386   4457870   4500166

To enhance the possibility of access the same table[index] concurrently,
set zram a small disksize(10MB) and let threads run with large loop
count.

fio test:
fio --bs=32k --randrepeat=1 --randseed=100 --refill_buffers
--scramble_buffers=1 --direct=1 --loops=3000 --numjobs=4
--filename=/dev/zram0 --name=seq-write --rw=write --stonewall
--name=seq-read --rw=read --stonewall --name=seq-readwrite
--rw=rw --stonewall --name=rand-readwrite --rw=randrw --stonewall
(10MB zram raw block device, take the average of 10 tests, KB/s)

    Test     base     CAS    spinlock    rwlock  bit_spinlock
-------------------------------------------------------------
seq-write   933789   999357   1003298    995961   1001958
 seq-read  5634130  6577930   6380861   6243912   6230006
   seq-rw  1405687  1638117   1640256   1633903   1634459
  rand-rw  1386119  1614664   1617211   1609267   1612471

All the optimization methods show a higher performance than the base,
however, it is hard to say which method is the most appropriate.

On the other hand, zram is mostly used on small embedded system, so we
don't want to increase any memory footprint.

This patch pick the bit_spinlock method, pack object size and page_flag
into an unsigned long table.value, so as to not increase any memory
overhead on both 32-bit and 64-bit system.

On the third hand, even though different kinds of locks have different
performances, we can ignore this difference, because: if zram is used as
zram swapfile, the swap subsystem can prevent concurrent access to the
same swapslot; if zram is used as zram-blk for set up filesystem on it,
the upper filesystem and the page cache also prevent concurrent access
of the same block mostly.  So we can ignore the different performances
among locks.

Acked-by: Sergey Senozhatsky &lt;sergey.senozhatsky@gmail.com&gt;
Reviewed-by: Davidlohr Bueso &lt;davidlohr@hp.com&gt;
Signed-off-by: Weijie Yang &lt;weijie.yang@samsung.com&gt;
Signed-off-by: Minchan Kim &lt;minchan@kernel.org&gt;
Cc: Jerome Marchand &lt;jmarchan@redhat.com&gt;
Cc: Nitin Gupta &lt;ngupta@vflare.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Currently, we use a rwlock tb_lock to protect concurrent access to the
whole zram meta table.  However, according to the actual access model,
there is only a small chance for upper user to access the same
table[index], so the current lock granularity is too big.

The idea of optimization is to change the lock granularity from whole
meta table to per table entry (table -&gt; table[index]), so that we can
protect concurrent access to the same table[index], meanwhile allow the
maximum concurrency.

With this in mind, several kinds of locks which could be used as a
per-entry lock were tested and compared:

Test environment:
x86-64 Intel Core2 Q8400, system memory 4GB, Ubuntu 12.04,
kernel v3.15.0-rc3 as base, zram with 4 max_comp_streams LZO.

iozone test:
iozone -t 4 -R -r 16K -s 200M -I +Z
(1GB zram with ext4 filesystem, take the average of 10 tests, KB/s)

      Test       base      CAS    spinlock    rwlock   bit_spinlock
-------------------------------------------------------------------
 Initial write  1381094   1425435   1422860   1423075   1421521
       Rewrite  1529479   1641199   1668762   1672855   1654910
          Read  8468009  11324979  11305569  11117273  10997202
       Re-read  8467476  11260914  11248059  11145336  10906486
  Reverse Read  6821393   8106334   8282174   8279195   8109186
   Stride read  7191093   8994306   9153982   8961224   9004434
   Random read  7156353   8957932   9167098   8980465   8940476
Mixed workload  4172747   5680814   5927825   5489578   5972253
  Random write  1483044   1605588   1594329   1600453   1596010
        Pwrite  1276644   1303108   1311612   1314228   1300960
         Pread  4324337   4632869   4618386   4457870   4500166

To enhance the possibility of access the same table[index] concurrently,
set zram a small disksize(10MB) and let threads run with large loop
count.

fio test:
fio --bs=32k --randrepeat=1 --randseed=100 --refill_buffers
--scramble_buffers=1 --direct=1 --loops=3000 --numjobs=4
--filename=/dev/zram0 --name=seq-write --rw=write --stonewall
--name=seq-read --rw=read --stonewall --name=seq-readwrite
--rw=rw --stonewall --name=rand-readwrite --rw=randrw --stonewall
(10MB zram raw block device, take the average of 10 tests, KB/s)

    Test     base     CAS    spinlock    rwlock  bit_spinlock
-------------------------------------------------------------
seq-write   933789   999357   1003298    995961   1001958
 seq-read  5634130  6577930   6380861   6243912   6230006
   seq-rw  1405687  1638117   1640256   1633903   1634459
  rand-rw  1386119  1614664   1617211   1609267   1612471

All the optimization methods show a higher performance than the base,
however, it is hard to say which method is the most appropriate.

On the other hand, zram is mostly used on small embedded system, so we
don't want to increase any memory footprint.

This patch pick the bit_spinlock method, pack object size and page_flag
into an unsigned long table.value, so as to not increase any memory
overhead on both 32-bit and 64-bit system.

On the third hand, even though different kinds of locks have different
performances, we can ignore this difference, because: if zram is used as
zram swapfile, the swap subsystem can prevent concurrent access to the
same swapslot; if zram is used as zram-blk for set up filesystem on it,
the upper filesystem and the page cache also prevent concurrent access
of the same block mostly.  So we can ignore the different performances
among locks.

Acked-by: Sergey Senozhatsky &lt;sergey.senozhatsky@gmail.com&gt;
Reviewed-by: Davidlohr Bueso &lt;davidlohr@hp.com&gt;
Signed-off-by: Weijie Yang &lt;weijie.yang@samsung.com&gt;
Signed-off-by: Minchan Kim &lt;minchan@kernel.org&gt;
Cc: Jerome Marchand &lt;jmarchan@redhat.com&gt;
Cc: Nitin Gupta &lt;ngupta@vflare.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>zram: use size_t instead of u16</title>
<updated>2014-08-07T01:01:23+00:00</updated>
<author>
<name>Minchan Kim</name>
<email>minchan@kernel.org</email>
</author>
<published>2014-08-06T23:08:29+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=023b409f9dac4cdea3322009f2e592068558690c'/>
<id>023b409f9dac4cdea3322009f2e592068558690c</id>
<content type='text'>
Some architectures (eg, hexagon and PowerPC) could use PAGE_SHIFT of 16
or more.  In these cases u16 is not sufficiently large to represent a
compressed page's size so use size_t.

Signed-off-by: Minchan Kim &lt;minchan@kernel.org&gt;
Reported-by: Weijie Yang &lt;weijie.yang@samsung.com&gt;
Acked-by: Sergey Senozhatsky &lt;sergey.senozhatsky@gmail.com&gt;
Cc: Jerome Marchand &lt;jmarchan@redhat.com&gt;
Cc: Nitin Gupta &lt;ngupta@vflare.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Some architectures (eg, hexagon and PowerPC) could use PAGE_SHIFT of 16
or more.  In these cases u16 is not sufficiently large to represent a
compressed page's size so use size_t.

Signed-off-by: Minchan Kim &lt;minchan@kernel.org&gt;
Reported-by: Weijie Yang &lt;weijie.yang@samsung.com&gt;
Acked-by: Sergey Senozhatsky &lt;sergey.senozhatsky@gmail.com&gt;
Cc: Jerome Marchand &lt;jmarchan@redhat.com&gt;
Cc: Nitin Gupta &lt;ngupta@vflare.org&gt;
Signed-off-by: Andrew Morton &lt;akpm@linux-foundation.org&gt;
Signed-off-by: Linus Torvalds &lt;torvalds@linux-foundation.org&gt;
</pre>
</div>
</content>
</entry>
</feed>
