1962406 - Buffer allocator medium allocations store metadata as part of the allocation

Status: RESOLVED FIXED

(Core :: JavaScript: GC, enhancement, P3)

Description

[Jon Coppeard (:jonco)]

Following on from bug 1960811 we can do a similar thing for medium sized buffers and store their metadata packed in the chunk header rather than at the start of the allocation.

Comment 1

[Jon Coppeard (:jonco)]

Attachment: Bug 1962406 - Part 1: Fix out-of-date comment that talks about large buffer headers r?sfink

These were removed previously in bug 1960811.

Comment 2

[Jon Coppeard (:jonco)]

Attachment: Bug 1962406 - Part 2: Rename 'ptr' to 'alloc' everywhere it's used for a buffer allocator allocation r?sfink

Standardizes on one term for the pointer to allocated memory return to the client.

Comment 3

[Jon Coppeard (:jonco)]

Attachment: Bug 1962406 - Part 3: Rename 'header' to 'buffer' in buffer allocator code r?sfink

Header doesn't make sense now these are not always stored at the start of
allocation. The structures themselves are named like FooBuffer, so use 'buffer'
for these pointers everywhere.

Comment 4

[Jon Coppeard (:jonco)]

Attachment: Bug 1962406 - Part 4: Move nursery allocated flag from MeduimBuffer to a bitmap in the chunk header r?sfink

Comment 5

[Jon Coppeard (:jonco)]

Attachment: Bug 1962406 - Part 5: Move size class to an array in the chunk header r?sfink

Comment 6

[Jon Coppeard (:jonco)]

Attachment: Bug 1962406 - Part 6: Remove medium buffer header r?sfink

Now we can remove the buffer header entirely. This is mostly a simplificiation.

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/30fa80635f50
Part 1: Fix out-of-date comment that talks about large buffer headers r=sfink
https://hg.mozilla.org/integration/autoland/rev/e66e33001e50
Part 2: Rename 'ptr' to 'alloc' everywhere it's used for a buffer allocator allocation r=sfink
https://hg.mozilla.org/integration/autoland/rev/2f8a3558e2c8
Part 3: Rename 'header' to 'buffer' in buffer allocator code r=sfink
https://hg.mozilla.org/integration/autoland/rev/55fb84dea632
Part 4: Move nursery allocated flag from MeduimBuffer to a bitmap in the chunk header r=sfink
https://hg.mozilla.org/integration/autoland/rev/717f6c86d1d4
Part 5: Move size class to an array in the chunk header r=sfink
https://hg.mozilla.org/integration/autoland/rev/4eac62f1e440
Part 6: Remove medium buffer header r=sfink

Comment 8

[Serban Stanca [:SerbanS]]

https://hg.mozilla.org/mozilla-central/rev/30fa80635f50
https://hg.mozilla.org/mozilla-central/rev/e66e33001e50
https://hg.mozilla.org/mozilla-central/rev/2f8a3558e2c8
https://hg.mozilla.org/mozilla-central/rev/55fb84dea632
https://hg.mozilla.org/mozilla-central/rev/717f6c86d1d4
https://hg.mozilla.org/mozilla-central/rev/4eac62f1e440

Comment 9

[Mayank Bansal]

7.5% improvement on Ares6-Basic_Average

Comment 10

[Florin Bilt]

(In reply to Serban Stanca [:SerbanS] from comment #8)

https://hg.mozilla.org/mozilla-central/rev/30fa80635f50
https://hg.mozilla.org/mozilla-central/rev/e66e33001e50
https://hg.mozilla.org/mozilla-central/rev/2f8a3558e2c8
https://hg.mozilla.org/mozilla-central/rev/55fb84dea632
https://hg.mozilla.org/mozilla-central/rev/717f6c86d1d4
https://hg.mozilla.org/mozilla-central/rev/4eac62f1e440

Perfherder has detected a talos performance change from push 4eac62f1e4409647b70eeb13aaab64bbfd6b2d61.

If you have any questions, please reach out to a performance sheriff. Alternatively, you can find help on Slack by joining #perf-help, and on Matrix you can find help by joining #perftest.

Improvements:

Ratio	Test	Platform	Options	Absolute values (old vs new)
6%	pdfpaint bug1826783.pdf	macosx1470-64-shippable	e10s fission stylo webrender-sw	550.57 -> 516.65

Details of the alert can be found in the alert summary, including links to graphs and comparisons for each of the affected tests.

If you need the profiling jobs you can trigger them yourself from treeherder job view or ask a performance sheriff to do that for you.

You can run all of these tests on try with ./mach try perf --alert 45069

The following documentation link provides more information about this command.