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c1437332e4
When looking at flamegraphs, there is a pretty large entry for the
function call drop_in_place::<Option<Allocation>> which in turn calls
drop_in_place::<Allocation>. Combined with the looper_need_return
condition, this means that the generated code looks like this:
if let Some(buffer) = buffer {
if buffer.looper_need_return_on_free() {
self.inner.lock().looper_need_return = true;
}
}
drop_in_place::<Option<Allocation>>() { // not inlined
if let Some(buffer) = buffer {
drop_in_place::<Allocation>(buffer);
}
}
This kind of situation where you check X and then check X again is
normally optimized into a single condition, but in this case due to the
non-inlined function call to drop_in_place::<Option<Allocation>>, that
optimization does not happen.
Furthermore, the drop_in_place::<Allocation> call is only two-thirds of
the drop_in_place::<Option<Allocation>> call in the flamegraph. This
indicates that this double condition is not performing well. Also, last
time I looked at Binder perf, I remember finding that the destructor of
Allocation was involved with many branch mispredictions.
Thus, change this code to look like this:
if let Some(buffer) = buffer {
if buffer.looper_need_return_on_free() {
self.inner.lock().looper_need_return = true;
}
drop_in_place::<Allocation>(buffer);
}
by dropping the Allocation directly. Flamegraphs confirm that the
drop_in_place::<Option<Allocation>> call disappears from this change.
Signed-off-by: Alice Ryhl <aliceryhl@google.com>
Acked-by: Carlos Llamas <cmllamas@google.com>
Link: https://patch.msgid.link/20251029-binder-bcfreebuf-option-v1-1-4d282be0439f@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
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| certs | ||
| crypto | ||
| Documentation | ||
| drivers | ||
| fs | ||
| include | ||
| init | ||
| io_uring | ||
| ipc | ||
| kernel | ||
| lib | ||
| LICENSES | ||
| mm | ||
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| tools | ||
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| virt | ||
| .clang-format | ||
| .clippy.toml | ||
| .cocciconfig | ||
| .editorconfig | ||
| .get_maintainer.ignore | ||
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| .gitignore | ||
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| README | ||
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the reStructuredText markup notation.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.