<feed xmlns='http://www.w3.org/2005/Atom'>
<title>linux-toradex.git/fs/ext4/sysfs.c, branch v5.13</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>ext4: Only advertise encrypted_casefold when encryption and unicode are enabled</title>
<updated>2021-06-06T14:10:23+00:00</updated>
<author>
<name>Daniel Rosenberg</name>
<email>drosen@google.com</email>
</author>
<published>2021-06-03T09:48:49+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=e71f99f2dfb45f4e7203a0732e85f71ef1d04dab'/>
<id>e71f99f2dfb45f4e7203a0732e85f71ef1d04dab</id>
<content type='text'>
Encrypted casefolding is only supported when both encryption and
casefolding are both enabled in the config.

Fixes: 471fbbea7ff7 ("ext4: handle casefolding with encryption")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Daniel Rosenberg &lt;drosen@google.com&gt;
Link: https://lore.kernel.org/r/20210603094849.314342-1-drosen@google.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Encrypted casefolding is only supported when both encryption and
casefolding are both enabled in the config.

Fixes: 471fbbea7ff7 ("ext4: handle casefolding with encryption")
Cc: stable@vger.kernel.org # 5.13+
Signed-off-by: Daniel Rosenberg &lt;drosen@google.com&gt;
Link: https://lore.kernel.org/r/20210603094849.314342-1-drosen@google.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext4: add proc files to monitor new structures</title>
<updated>2021-04-09T15:34:59+00:00</updated>
<author>
<name>Harshad Shirwadkar</name>
<email>harshadshirwadkar@gmail.com</email>
</author>
<published>2021-04-01T17:21:28+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=f68f4063855903fd3a279e646451eab04db0655f'/>
<id>f68f4063855903fd3a279e646451eab04db0655f</id>
<content type='text'>
This patch adds a new file "mb_structs_summary" which allows us to see
the summary of the new allocator structures added in this
series. Here's the sample output of file:

optimize_scan: 1
max_free_order_lists:
        list_order_0_groups: 0
        list_order_1_groups: 0
        list_order_2_groups: 0
        list_order_3_groups: 0
        list_order_4_groups: 0
        list_order_5_groups: 0
        list_order_6_groups: 0
        list_order_7_groups: 0
        list_order_8_groups: 0
        list_order_9_groups: 0
        list_order_10_groups: 0
        list_order_11_groups: 0
        list_order_12_groups: 0
        list_order_13_groups: 40
fragment_size_tree:
        tree_min: 16384
        tree_max: 32768
        tree_nodes: 40

Signed-off-by: Harshad Shirwadkar &lt;harshadshirwadkar@gmail.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Reviewed-by: Ritesh Harjani &lt;ritesh.list@gmail.com&gt;
Link: https://lore.kernel.org/r/20210401172129.189766-7-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This patch adds a new file "mb_structs_summary" which allows us to see
the summary of the new allocator structures added in this
series. Here's the sample output of file:

optimize_scan: 1
max_free_order_lists:
        list_order_0_groups: 0
        list_order_1_groups: 0
        list_order_2_groups: 0
        list_order_3_groups: 0
        list_order_4_groups: 0
        list_order_5_groups: 0
        list_order_6_groups: 0
        list_order_7_groups: 0
        list_order_8_groups: 0
        list_order_9_groups: 0
        list_order_10_groups: 0
        list_order_11_groups: 0
        list_order_12_groups: 0
        list_order_13_groups: 40
fragment_size_tree:
        tree_min: 16384
        tree_max: 32768
        tree_nodes: 40

Signed-off-by: Harshad Shirwadkar &lt;harshadshirwadkar@gmail.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Reviewed-by: Ritesh Harjani &lt;ritesh.list@gmail.com&gt;
Link: https://lore.kernel.org/r/20210401172129.189766-7-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext4: improve cr 0 / cr 1 group scanning</title>
<updated>2021-04-09T15:34:59+00:00</updated>
<author>
<name>Harshad Shirwadkar</name>
<email>harshadshirwadkar@gmail.com</email>
</author>
<published>2021-04-01T17:21:27+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=196e402adf2e4cd66f101923409f1970ec5f1af3'/>
<id>196e402adf2e4cd66f101923409f1970ec5f1af3</id>
<content type='text'>
Instead of traversing through groups linearly, scan groups in specific
orders at cr 0 and cr 1. At cr 0, we want to find groups that have the
largest free order &gt;= the order of the request. So, with this patch,
we maintain lists for each possible order and insert each group into a
list based on the largest free order in its buddy bitmap. During cr 0
allocation, we traverse these lists in the increasing order of largest
free orders. This allows us to find a group with the best available cr
0 match in constant time. If nothing can be found, we fallback to cr 1
immediately.

At CR1, the story is slightly different. We want to traverse in the
order of increasing average fragment size. For CR1, we maintain a rb
tree of groupinfos which is sorted by average fragment size. Instead
of traversing linearly, at CR1, we traverse in the order of increasing
average fragment size, starting at the most optimal group. This brings
down cr 1 search complexity to log(num groups).

For cr &gt;= 2, we just perform the linear search as before. Also, in
case of lock contention, we intermittently fallback to linear search
even in CR 0 and CR 1 cases. This allows us to proceed during the
allocation path even in case of high contention.

There is an opportunity to do optimization at CR2 too. That's because
at CR2 we only consider groups where bb_free counter (number of free
blocks) is greater than the request extent size. That's left as future
work.

All the changes introduced in this patch are protected under a new
mount option "mb_optimize_scan".

With this patchset, following experiment was performed:

Created a highly fragmented disk of size 65TB. The disk had no
contiguous 2M regions. Following command was run consecutively for 3
times:

time dd if=/dev/urandom of=file bs=2M count=10

Here are the results with and without cr 0/1 optimizations introduced
in this patch:

|---------+------------------------------+---------------------------|
|         | Without CR 0/1 Optimizations | With CR 0/1 Optimizations |
|---------+------------------------------+---------------------------|
| 1st run | 5m1.871s                     | 2m47.642s                 |
| 2nd run | 2m28.390s                    | 0m0.611s                  |
| 3rd run | 2m26.530s                    | 0m1.255s                  |
|---------+------------------------------+---------------------------|

Signed-off-by: Harshad Shirwadkar &lt;harshadshirwadkar@gmail.com&gt;
Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Reported-by: Dan Carpenter &lt;dan.carpenter@oracle.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Link: https://lore.kernel.org/r/20210401172129.189766-6-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Instead of traversing through groups linearly, scan groups in specific
orders at cr 0 and cr 1. At cr 0, we want to find groups that have the
largest free order &gt;= the order of the request. So, with this patch,
we maintain lists for each possible order and insert each group into a
list based on the largest free order in its buddy bitmap. During cr 0
allocation, we traverse these lists in the increasing order of largest
free orders. This allows us to find a group with the best available cr
0 match in constant time. If nothing can be found, we fallback to cr 1
immediately.

At CR1, the story is slightly different. We want to traverse in the
order of increasing average fragment size. For CR1, we maintain a rb
tree of groupinfos which is sorted by average fragment size. Instead
of traversing linearly, at CR1, we traverse in the order of increasing
average fragment size, starting at the most optimal group. This brings
down cr 1 search complexity to log(num groups).

For cr &gt;= 2, we just perform the linear search as before. Also, in
case of lock contention, we intermittently fallback to linear search
even in CR 0 and CR 1 cases. This allows us to proceed during the
allocation path even in case of high contention.

There is an opportunity to do optimization at CR2 too. That's because
at CR2 we only consider groups where bb_free counter (number of free
blocks) is greater than the request extent size. That's left as future
work.

All the changes introduced in this patch are protected under a new
mount option "mb_optimize_scan".

With this patchset, following experiment was performed:

Created a highly fragmented disk of size 65TB. The disk had no
contiguous 2M regions. Following command was run consecutively for 3
times:

time dd if=/dev/urandom of=file bs=2M count=10

Here are the results with and without cr 0/1 optimizations introduced
in this patch:

|---------+------------------------------+---------------------------|
|         | Without CR 0/1 Optimizations | With CR 0/1 Optimizations |
|---------+------------------------------+---------------------------|
| 1st run | 5m1.871s                     | 2m47.642s                 |
| 2nd run | 2m28.390s                    | 0m0.611s                  |
| 3rd run | 2m26.530s                    | 0m1.255s                  |
|---------+------------------------------+---------------------------|

Signed-off-by: Harshad Shirwadkar &lt;harshadshirwadkar@gmail.com&gt;
Reported-by: kernel test robot &lt;lkp@intel.com&gt;
Reported-by: Dan Carpenter &lt;dan.carpenter@oracle.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Link: https://lore.kernel.org/r/20210401172129.189766-6-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext4: add mballoc stats proc file</title>
<updated>2021-04-09T15:34:59+00:00</updated>
<author>
<name>Harshad Shirwadkar</name>
<email>harshadshirwadkar@gmail.com</email>
</author>
<published>2021-04-01T17:21:25+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=a6c75eaf11032f4a3d2b3ce2265a194ac6e4a7f0'/>
<id>a6c75eaf11032f4a3d2b3ce2265a194ac6e4a7f0</id>
<content type='text'>
Add new stats for measuring the performance of mballoc. This patch is
forked from Artem Blagodarenko's work that can be found here:

https://github.com/lustre/lustre-release/blob/master/ldiskfs/kernel_patches/patches/rhel8/ext4-simple-blockalloc.patch

This patch reorganizes the stats by cr level. This is how the output
looks like:

mballoc:
	reqs: 0
	success: 0
	groups_scanned: 0
	cr0_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
		bad_suggestions: 0
	cr1_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
		bad_suggestions: 0
	cr2_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
	cr3_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
	extents_scanned: 0
		goal_hits: 0
		2^n_hits: 0
		breaks: 0
		lost: 0
	buddies_generated: 0/40
	buddies_time_used: 0
	preallocated: 0
	discarded: 0

Signed-off-by: Harshad Shirwadkar &lt;harshadshirwadkar@gmail.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Reviewed-by: Ritesh Harjani &lt;ritesh.list@gmail.com&gt;
Link: https://lore.kernel.org/r/20210401172129.189766-4-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Add new stats for measuring the performance of mballoc. This patch is
forked from Artem Blagodarenko's work that can be found here:

https://github.com/lustre/lustre-release/blob/master/ldiskfs/kernel_patches/patches/rhel8/ext4-simple-blockalloc.patch

This patch reorganizes the stats by cr level. This is how the output
looks like:

mballoc:
	reqs: 0
	success: 0
	groups_scanned: 0
	cr0_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
		bad_suggestions: 0
	cr1_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
		bad_suggestions: 0
	cr2_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
	cr3_stats:
		hits: 0
		groups_considered: 0
		useless_loops: 0
	extents_scanned: 0
		goal_hits: 0
		2^n_hits: 0
		breaks: 0
		lost: 0
	buddies_generated: 0/40
	buddies_time_used: 0
	preallocated: 0
	discarded: 0

Signed-off-by: Harshad Shirwadkar &lt;harshadshirwadkar@gmail.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Reviewed-by: Ritesh Harjani &lt;ritesh.list@gmail.com&gt;
Link: https://lore.kernel.org/r/20210401172129.189766-4-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext4: handle casefolding with encryption</title>
<updated>2021-04-06T02:04:20+00:00</updated>
<author>
<name>Daniel Rosenberg</name>
<email>drosen@google.com</email>
</author>
<published>2021-03-19T07:34:13+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=471fbbea7ff7061b2d6474665cb5a2ceb4fd6500'/>
<id>471fbbea7ff7061b2d6474665cb5a2ceb4fd6500</id>
<content type='text'>
This adds support for encryption with casefolding.

Since the name on disk is case preserving, and also encrypted, we can no
longer just recompute the hash on the fly. Additionally, to avoid
leaking extra information from the hash of the unencrypted name, we use
siphash via an fscrypt v2 policy.

The hash is stored at the end of the directory entry for all entries
inside of an encrypted and casefolded directory apart from those that
deal with '.' and '..'. This way, the change is backwards compatible
with existing ext4 filesystems.

[ Changed to advertise this feature via the file:
  /sys/fs/ext4/features/encrypted_casefold -- TYT ]

Signed-off-by: Daniel Rosenberg &lt;drosen@google.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Link: https://lore.kernel.org/r/20210319073414.1381041-2-drosen@google.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This adds support for encryption with casefolding.

Since the name on disk is case preserving, and also encrypted, we can no
longer just recompute the hash on the fly. Additionally, to avoid
leaking extra information from the hash of the unencrypted name, we use
siphash via an fscrypt v2 policy.

The hash is stored at the end of the directory entry for all entries
inside of an encrypted and casefolded directory apart from those that
deal with '.' and '..'. This way, the change is backwards compatible
with existing ext4 filesystems.

[ Changed to advertise this feature via the file:
  /sys/fs/ext4/features/encrypted_casefold -- TYT ]

Signed-off-by: Daniel Rosenberg &lt;drosen@google.com&gt;
Reviewed-by: Andreas Dilger &lt;adilger@dilger.ca&gt;
Link: https://lore.kernel.org/r/20210319073414.1381041-2-drosen@google.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext4: shrink race window in ext4_should_retry_alloc()</title>
<updated>2021-03-06T16:56:10+00:00</updated>
<author>
<name>Eric Whitney</name>
<email>enwlinux@gmail.com</email>
</author>
<published>2021-02-18T15:11:32+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=efc61345274d6c7a46a0570efbc916fcbe3e927b'/>
<id>efc61345274d6c7a46a0570efbc916fcbe3e927b</id>
<content type='text'>
When generic/371 is run on kvm-xfstests using 5.10 and 5.11 kernels, it
fails at significant rates on the two test scenarios that disable
delayed allocation (ext3conv and data_journal) and force actual block
allocation for the fallocate and pwrite functions in the test.  The
failure rate on 5.10 for both ext3conv and data_journal on one test
system typically runs about 85%.  On 5.11, the failure rate on ext3conv
sometimes drops to as low as 1% while the rate on data_journal
increases to nearly 100%.

The observed failures are largely due to ext4_should_retry_alloc()
cutting off block allocation retries when s_mb_free_pending (used to
indicate that a transaction in progress will free blocks) is 0.
However, free space is usually available when this occurs during runs
of generic/371.  It appears that a thread attempting to allocate
blocks is just missing transaction commits in other threads that
increase the free cluster count and reset s_mb_free_pending while
the allocating thread isn't running.  Explicitly testing for free space
availability avoids this race.

The current code uses a post-increment operator in the conditional
expression that determines whether the retry limit has been exceeded.
This means that the conditional expression uses the value of the
retry counter before it's increased, resulting in an extra retry cycle.
The current code actually retries twice before hitting its retry limit
rather than once.

Increasing the retry limit to 3 from the current actual maximum retry
count of 2 in combination with the change described above reduces the
observed failure rate to less that 0.1% on both ext3conv and
data_journal with what should be limited impact on users sensitive to
the overhead caused by retries.

A per filesystem percpu counter exported via sysfs is added to allow
users or developers to track the number of times the retry limit is
exceeded without resorting to debugging methods.  This should provide
some insight into worst case retry behavior.

Signed-off-by: Eric Whitney &lt;enwlinux@gmail.com&gt;
Link: https://lore.kernel.org/r/20210218151132.19678-1-enwlinux@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
When generic/371 is run on kvm-xfstests using 5.10 and 5.11 kernels, it
fails at significant rates on the two test scenarios that disable
delayed allocation (ext3conv and data_journal) and force actual block
allocation for the fallocate and pwrite functions in the test.  The
failure rate on 5.10 for both ext3conv and data_journal on one test
system typically runs about 85%.  On 5.11, the failure rate on ext3conv
sometimes drops to as low as 1% while the rate on data_journal
increases to nearly 100%.

The observed failures are largely due to ext4_should_retry_alloc()
cutting off block allocation retries when s_mb_free_pending (used to
indicate that a transaction in progress will free blocks) is 0.
However, free space is usually available when this occurs during runs
of generic/371.  It appears that a thread attempting to allocate
blocks is just missing transaction commits in other threads that
increase the free cluster count and reset s_mb_free_pending while
the allocating thread isn't running.  Explicitly testing for free space
availability avoids this race.

The current code uses a post-increment operator in the conditional
expression that determines whether the retry limit has been exceeded.
This means that the conditional expression uses the value of the
retry counter before it's increased, resulting in an extra retry cycle.
The current code actually retries twice before hitting its retry limit
rather than once.

Increasing the retry limit to 3 from the current actual maximum retry
count of 2 in combination with the change described above reduces the
observed failure rate to less that 0.1% on both ext3conv and
data_journal with what should be limited impact on users sensitive to
the overhead caused by retries.

A per filesystem percpu counter exported via sysfs is added to allow
users or developers to track the number of times the retry limit is
exceeded without resorting to debugging methods.  This should provide
some insight into worst case retry behavior.

Signed-off-by: Eric Whitney &lt;enwlinux@gmail.com&gt;
Link: https://lore.kernel.org/r/20210218151132.19678-1-enwlinux@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>block: switch partition lookup to use struct block_device</title>
<updated>2020-12-01T21:53:40+00:00</updated>
<author>
<name>Christoph Hellwig</name>
<email>hch@lst.de</email>
</author>
<published>2020-11-24T08:36:54+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=8446fe9255be821cb38ffd306d7e8edc4b9ea662'/>
<id>8446fe9255be821cb38ffd306d7e8edc4b9ea662</id>
<content type='text'>
Use struct block_device to lookup partitions on a disk.  This removes
all usage of struct hd_struct from the I/O path.

Signed-off-by: Christoph Hellwig &lt;hch@lst.de&gt;
Reviewed-by: Jan Kara &lt;jack@suse.cz&gt;
Reviewed-by: Hannes Reinecke &lt;hare@suse.de&gt;
Acked-by: Coly Li &lt;colyli@suse.de&gt;			[bcache]
Acked-by: Chao Yu &lt;yuchao0@huawei.com&gt;			[f2fs]
Signed-off-by: Jens Axboe &lt;axboe@kernel.dk&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Use struct block_device to lookup partitions on a disk.  This removes
all usage of struct hd_struct from the I/O path.

Signed-off-by: Christoph Hellwig &lt;hch@lst.de&gt;
Reviewed-by: Jan Kara &lt;jack@suse.cz&gt;
Reviewed-by: Hannes Reinecke &lt;hare@suse.de&gt;
Acked-by: Coly Li &lt;colyli@suse.de&gt;			[bcache]
Acked-by: Chao Yu &lt;yuchao0@huawei.com&gt;			[f2fs]
Signed-off-by: Jens Axboe &lt;axboe@kernel.dk&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext4: indicate that fast_commit is available via /sys/fs/ext4/feature/...</title>
<updated>2020-10-28T17:43:22+00:00</updated>
<author>
<name>Theodore Ts'o</name>
<email>tytso@mit.edu</email>
</author>
<published>2020-10-28T17:39:13+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=6694875ef8045cdb1e6712ee9b68fe08763507d8'/>
<id>6694875ef8045cdb1e6712ee9b68fe08763507d8</id>
<content type='text'>
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext4: add fast commit stats in procfs</title>
<updated>2020-10-22T03:22:38+00:00</updated>
<author>
<name>Harshad Shirwadkar</name>
<email>harshadshirwadkar@gmail.com</email>
</author>
<published>2020-10-15T20:38:01+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=ce8c59d197c824789e1ade6f25d36037b4f0faeb'/>
<id>ce8c59d197c824789e1ade6f25d36037b4f0faeb</id>
<content type='text'>
This commit adds a file in procfs that tracks fast commit related
statistics.

root@kvm-xfstests:/mnt# cat /proc/fs/ext4/vdc/fc_info
fc stats:
7772 commits
15 ineligible
4083 numblks
2242us avg_commit_time
Ineligible reasons:
"Extended attributes changed":  0
"Cross rename": 0
"Journal flag changed": 0
"Insufficient memory":  0
"Swap boot":    0
"Resize":       0
"Dir renamed":  0
"Falloc range op":      0
"FC Commit Failed":     15

Signed-off-by: Harshad Shirwadkar &lt;harshadshirwadkar@gmail.com&gt;
Link: https://lore.kernel.org/r/20201015203802.3597742-10-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
This commit adds a file in procfs that tracks fast commit related
statistics.

root@kvm-xfstests:/mnt# cat /proc/fs/ext4/vdc/fc_info
fc stats:
7772 commits
15 ineligible
4083 numblks
2242us avg_commit_time
Ineligible reasons:
"Extended attributes changed":  0
"Cross rename": 0
"Journal flag changed": 0
"Insufficient memory":  0
"Swap boot":    0
"Resize":       0
"Dir renamed":  0
"Falloc range op":      0
"FC Commit Failed":     15

Signed-off-by: Harshad Shirwadkar &lt;harshadshirwadkar@gmail.com&gt;
Link: https://lore.kernel.org/r/20201015203802.3597742-10-harshadshirwadkar@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</pre>
</div>
</content>
</entry>
<entry>
<title>ext4: limit the length of per-inode prealloc list</title>
<updated>2020-08-19T16:04:36+00:00</updated>
<author>
<name>brookxu</name>
<email>brookxu.cn@gmail.com</email>
</author>
<published>2020-08-17T07:36:15+00:00</published>
<link rel='alternate' type='text/html' href='https://git.toradex.cn/cgit/linux-toradex.git/commit/?id=27bc446e2def38db3244a6eb4bb1d6312936610a'/>
<id>27bc446e2def38db3244a6eb4bb1d6312936610a</id>
<content type='text'>
In the scenario of writing sparse files, the per-inode prealloc list may
be very long, resulting in high overhead for ext4_mb_use_preallocated().
To circumvent this problem, we limit the maximum length of per-inode
prealloc list to 512 and allow users to modify it.

After patching, we observed that the sys ratio of cpu has dropped, and
the system throughput has increased significantly. We created a process
to write the sparse file, and the running time of the process on the
fixed kernel was significantly reduced, as follows:

Running time on unfixed kernel：
[root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat
real    0m2.051s
user    0m0.008s
sys     0m2.026s

Running time on fixed kernel：
[root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat
real    0m0.471s
user    0m0.004s
sys     0m0.395s

Signed-off-by: Chunguang Xu &lt;brookxu@tencent.com&gt;
Link: https://lore.kernel.org/r/d7a98178-056b-6db5-6bce-4ead23f4a257@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</content>
<content type='xhtml'>
<div xmlns='http://www.w3.org/1999/xhtml'>
<pre>
In the scenario of writing sparse files, the per-inode prealloc list may
be very long, resulting in high overhead for ext4_mb_use_preallocated().
To circumvent this problem, we limit the maximum length of per-inode
prealloc list to 512 and allow users to modify it.

After patching, we observed that the sys ratio of cpu has dropped, and
the system throughput has increased significantly. We created a process
to write the sparse file, and the running time of the process on the
fixed kernel was significantly reduced, as follows:

Running time on unfixed kernel：
[root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat
real    0m2.051s
user    0m0.008s
sys     0m2.026s

Running time on fixed kernel：
[root@TENCENT64 ~]# time taskset 0x01 ./sparse /data1/sparce.dat
real    0m0.471s
user    0m0.004s
sys     0m0.395s

Signed-off-by: Chunguang Xu &lt;brookxu@tencent.com&gt;
Link: https://lore.kernel.org/r/d7a98178-056b-6db5-6bce-4ead23f4a257@gmail.com
Signed-off-by: Theodore Ts'o &lt;tytso@mit.edu&gt;
</pre>
</div>
</content>
</entry>
</feed>
