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f6ecf80ebb
The documentation grew one page at a time, so the tree follows the
history of who wrote what and not the shape of NuttX. Scheduling is
spread over three places, a driver page can sit above the subsystem
that owns it, and the front page lists everything at the same level.
That is a lot to face when all you want to know is where the scheduler
lives.
This change files every page under the code it describes. It is a move,
not a rewrite: outside the ten pages named below, every page keeps the
text that is already in master, and no page's text is deleted.
What it does:
* Groups the table of contents into nine chapters.
* Moves the OS subsystems under os/: scheduling, memory, drivers,
filesystem, networking, IPC, interrupts, libs, time.
* Renames the platform pages to the names the source tree uses, and
derives their tags from the tree instead of by hand.
* Splits guides/ by subject.
* Adds Documentation/redirects.py, with a rule for every page that left
its old path, so old URLs keep working. The redirect page also carries
a link's #anchor across to the new page.
Ten pages have text that is new or rewritten. Nine of them are the
landing page of a chapter, which has to exist for the new structure:
index the front page
os/index OS Design
os/scheduling/index Scheduling
os/interrupts/index Interrupts
os/ipc/index IPC
os/time/index Time and timers
about/index About
developing/index Developing NuttX
ReleaseNotes/index Release notes
The tenth is os/libs/libbuiltin, the only page here with technical
content: libs/libbuiltin/ had no page at all. Five SVG diagrams come
with these pages, hand-written XML with no editor metadata.
Nothing outside Documentation/ is touched.
How it was checked:
* Sphinx builds with -W: no warnings, and no document left outside a
toctree.
* A script, offered in the PR, proves the narrow claim this rests on.
For every page outside the ten named above it erases what a move
touches -- link target, path, tag line, toctree block, table border --
from the whole old text and the whole new text, and requires the two
to be byte for byte identical. It also requires every sentence of a
deleted page to turn up somewhere, and every page that left its old
path to have a redirect, from a URL that existed, to where its content
went. It exits non-zero and names the page if any of that is not true,
and it tests added pages too, so forgetting to declare one cannot make
it pass.
* An independent audit checked 133 factual claims on these ten pages
against the tree, one shell command per claim: 130 confirmed, 1
refuted and fixed here, 2 not checkable.
* tools/checkpatch.sh is clean over the range.
The diff is large because moving a page changes every link that points
to it. Most of it is pure renames, and board pages that gained one tag
line.
Assisted-by: Claude:claude-opus-5
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ReStructuredText
38 lines
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ReStructuredText
==============================
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VFS Performance Profiler
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==============================
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The Virtual File System (VFS) Performance Profiler provides a simple, in-kernel
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mechanism to track execution times and invocation counts for core VFS operations
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(read, write, open, close) seamlessly. This is highly suitable for
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CI/CD automated regression testing and performance bottleneck identification.
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Configuration
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=============
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To enable the profiler, select ``CONFIG_FS_PROFILER`` in your Kconfig.
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To expose the metrics dynamically via procfs, ensure ``CONFIG_FS_PROCFS`` is enabled, and
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the profiler node is included via ``CONFIG_FS_PROCFS_PROFILER``.
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Usage
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=====
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When enabled, the profiler automatically intercepts calls to the underlying
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inode operations and records the execution elapsed times using ``perf_gettime()``.
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Since no blocking mutexes are used during updates (fast ``atomic.h`` operations
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are utilized instead), the overhead is extremely minimal and safely scales on SMP.
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To view the current statistics collectively from the NuttShell (NSH), simply
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read the node:
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.. code-block:: bash
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nsh> cat /proc/fs/profile
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VFS Performance Profile:
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Reads: 12 (Total time: 4500120 ns)
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Writes: 3 (Total time: 95050 ns)
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Opens: 15 (Total time: 1005000 ns)
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Closes: 15 (Total time: 45000 ns)
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The reported times are in the raw ticks/units provided by ``perf_gettime()`` on
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your specific architecture.
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