This reduces memory usage because we only need one allocation instead of two
for the dynamic atom and its chars, and because we don't need to store a
refcount and a size. It precludes sharing of chars between dynamic atoms, but
we weren't benefiting much from that anyway.
This reduces per-process memory usage by up to several hundred KiB on my
Linux64 box.
One consequence of this change is that we need to allocate + copy in
DOMString::SetKnownLiveAtom(), which could make some things slower.
The about:memory page specified some colours using constants and others
using variables whose values can change. If those variables changed, for
example due to the desktop toolkit using a dark theme, then it could create
poor contrast with the constants in these CSS files (desktop & mobile).
This change ensures that only the Mozilla system colour extensions and
Mozilla colour preference extensions colours are used. Creating
fore/back-ground combinations that hopefully contrast well regardless of the
desktop theme.
Unfortunately, I wasn't able to figure out a way to make firefox build & run in
the intermediate stages of these commits. Because of this, I am going to just
delete most of the code which I am deleting in the first patch, as I figure that
those are somewhat uninteresting changes, and then make the other changes in the
following patches.
In total, the following things are deleted:
1. All of xpcom/typelib, except for `xpt/tools` - this directory is being
subsumed entirely into xpcom/reflect/xptinfo.
2. Most of the code in xpcom/reflect/xptinfo, it is being rewritten to avoid
allocating and contain all of the necessary data structures.
3. idl-parser's typelib.py XPT generator, as it will be replaced.
4. Most includes of files which have been deleted.
NOTE: xpcom/typelib/xpt/tools/xpt.py was not removed, as it is used by bundling
code & bundling tests, which we don't want to remove yet.
Currently static atoms are stored on the heap, but their char buffers are
stored in read-only static memory.
This patch changes the representation of nsStaticAtom (thus making it a
non-trivial subclass of nsAtom). Instead of a pointer to the string, it now has
an mStringOffset field which is a 32-bit offset to the string. (This requires
placement of the string and the atom within the same object so that the offset
is known to be small. The docs and macros in nsStaticAtom.h handle that.)
Static and dynamic atoms now store their chars in different ways: nsStaticAtom
stores them inline, nsDynamicAtom has a pointer to separate storage. So
`mString` and GetStringBuffer() move from nsAtom to nsDynamicAtom.
The change to static atoms means they can be made constexpr and stored in
read-only memory instead of on the heap. On 64-bit this reduces the per-process
overhead by 16 bytes; on 32-bit the saving is 12 bytes. (Further reductions
will be possible in follow-up patches.)
The increased use of constexpr required multiple workarounds for MSVC.
- Multiple uses of MOZ_{PUSH,POP}_DISABLE_INTEGRAL_CONSTANT_OVERFLOW_WARNING to
disable warnings about (well-defined!) overflow of unsigned integer
arithmetic.
- The use of -Zc:externConstexpr on all files defining static atoms, to make
MSVC follow the C++ standard(!) and let constexpr variables have external
linkage.
- The use of -constexpr:steps300000 to increase the number of operations
allowed in a constexpr value, in order to handle gGkAtoms, which requires
hashing ~2,500 atom strings.
The patch also changes how HTML5 atoms are handled. They are now treated as
dynamic atoms, i.e. we have "dynamic normal" atoms and "dynamic HTML5 atoms",
and "dynamic atoms" covers both cases, and both are represented via
nsDynamicAtom. The main difference between the two kinds is that dynamic HTML5
atoms still aren't allowed to be used in various operations, most notably
AddRef()/Release(). All this also required moving nsDynamicAtom into the header
file.
There is a slight performance cost to all these changes: now that nsStaticAtom
and nsDynamicAtom store their chars in different ways, a conditional branch is
required in the following functions: Equals(), GetUTF16String(),
WeakAtom::as_slice().
Finally, in about:memory the "explicit/atoms/static/atom-objects" value is no
longer needed, because that memory is static instead of heap-allocated.
MozReview-Commit-ID: 4AxPv05ngZy
The old output had a single value: "atoms-table". The new output looks like
this:
> 649,904 B (00.39%) -- atoms
> ├──350,256 B (00.21%) -- dynamic
> │ ├──235,056 B (00.14%) ── unshared-buffers
> │ └──115,200 B (00.07%) ── atom-objects
> ├──212,992 B (00.13%) ── table
> └───86,656 B (00.05%) ── static/atom-objects
MozReview-Commit-ID: 924vUmxHAlh
Various atom-related things have improved recently.
- The main atom table is now threadsafe (bug 1275755) and so can be accessed on
any thread. It has also been split into pieces (bug 1440824), which greatly
reduces lock contention.
- A cache has been added to the HTML5 parser (bug 1352874) that removes the
need for most of the full table lookups.
As a result, there is no point having a separate static atom table. This patch
removes it.
MozReview-Commit-ID: 8ou1BrnPAwd
This patch was autogenerated by my decomponents.py
It covers almost every file with the extension js, jsm, html, py,
xhtml, or xul.
It removes blank lines after removed lines, when the removed lines are
preceded by either blank lines or the start of a new block. The "start
of a new block" is defined fairly hackily: either the line starts with
//, ends with */, ends with {, <![CDATA[, """ or '''. The first two
cover comments, the third one covers JS, the fourth covers JS embedded
in XUL, and the final two cover JS embedded in Python. This also
applies if the removed line was the first line of the file.
It covers the pattern matching cases like "var {classes: Cc,
interfaces: Ci, utils: Cu, results: Cr} = Components;". It'll remove
the entire thing if they are all either Ci, Cr, Cc or Cu, or it will
remove the appropriate ones and leave the residue behind. If there's
only one behind, then it will turn it into a normal, non-pattern
matching variable definition. (For instance, "const { classes: Cc,
Constructor: CC, interfaces: Ci, utils: Cu } = Components" becomes
"const CC = Components.Constructor".)
MozReview-Commit-ID: DeSHcClQ7cG
This was created for B2G and isn't really useful otherwise. It only works on
Linux, and it's behind the memory.system_memory_reporter pref, which is false
by default.
The patch also removes LinuxUtils.{h,cpp}, which is no longer used.
nsIHandleReportCallback, typedef of nsIMemoryReporterCallback, has been the
preferred name for a long time and is used in most places. This patch removes
nsIMemoryReporterCallback.
This patch is generated by the following sed script:
find . ! -wholename '*/.hg*' -type f \( -iname '*.html' -o -iname '*.xhtml' -o -iname '*.xul' -o -iname '*.js' \) -exec sed -i -e 's/\(\(text\|application\)\/javascript\);version=1.[0-9]/\1/g' {} \;
MozReview-Commit-ID: AzhtdwJwVNg
