1867191 - Set the PHC memory area size from a pref

Status: RESOLVED FIXED

(Core :: Memory Allocator, task)

Comment 1

[Paul Bone [:pbone]]

Attachment: Bug 1867191 - pt 1. Changes to PHC pointer tests

To allow the PHC arena size to be dynamic the reserved memory range may
be larger than the actual memory allocated by PHC. To keep the fast-path
as fast as possible this patch replaces the initial PtrKind() query with a
bounds check. The bounds check can be done without a lock. A later
step will determine the PtrKind.

• Use a bounds check on the hot path for free, realloc and other
  functions that take a pointer, before calling the corresponding PHC::
  methods.

• The PHC method must assume it has a pointer that is in-bounds, but it
  can determine the kind of the pointer with GetPtrKind().

• Remove the Nothing PtrKind since it previously represented
  out-of-bounds pointers.

• Add branch annotations on the hot paths.

Comment 2

[Paul Bone [:pbone]]

Attachment: Bug 1867191 - pt 2. Use a custom array implementation for PHC's metadata r=glandium

PHC's metadata size is defined at compile-time. To relax this to
runtime we need to use a different array implementation that stores the
size in a member variable, rather than a template parameter.

Refactor how metadata size is calculated since it must capture the size
of this array. Separate methods like FragmentationBytes() and
AllocationBytes() have been merged to get a consistent read by taking
the lock only once.

Comment 3

[Paul Bone [:pbone]]

Attachment: Bug 1867191 - pt 3. PHC's size is no-longer fixed at compile time r=glandium

The size of PHC's allocation area is now set when the metadata is
created. The kNumAllocPages symbol is removed, instead a new
NumAllocPages() function will return the length of the AllocInfo array.

The array is protected by the PHC lock so now getting the true size
of the PHC area (rather than the virtual memory reservation that it's
inside) can only be done while holding the lock. Checking the index of
an allocation during free() against the upper bound is now down after
taking the lock.

Comment 4

[Paul Bone [:pbone]]

Attachment: WIP: Bug 1867191 - pt 4. Initialise PHC from mozjemalloc

PHC uses dynamic memory allocation* and so initialising it after
mozjemalloc makes sense, the easiest way to do this is to call it late
in mozjemalloc's initialisation.

*: it always has used dynamic memory, these patches add one additional
allocation. So this change isn't really necessary.

Comment 5

[Paul Bone [:pbone]]

Attachment: Bug 1867191 - pt 4. Add support for growing PHC's storage r=glandium

Comment 6

[Paul Bone [:pbone]]

Attachment: Bug 1867191 - pt 5. Control PHC's size from a pref r=glandium

This allows expanding the size of memory area used by PHC, but not
shrinking it.

Comment 7

[Paul Bone [:pbone]]

Attachment: Bug 1867191 - pt 6. Remove an unused function in PHC r=glandium

Comment 8

[Paul Bone [:pbone]]

Attachment: Bug 1867191 - pt 7. Fix a misspelt variable name r=glandium

Comment 9

[Paul Bone [:pbone]]

Attachment: Bug 1867191 - pt 6. Also support shrinking the PHC area

Comment 10

[Phabricator Automation]

Comment on attachment 9496683 [details]
WIP: Bug 1867191 - pt 4. Initialise PHC from mozjemalloc

Revision D254945 was moved to bug 1974931. Setting attachment 9496683 [details] to obsolete.

Comment 11

[Phabricator Automation]

Comment on attachment 9497599 [details]
Bug 1867191 - pt 7. Fix a misspelt variable name r=glandium

Revision D255489 was moved to bug 1975689. Setting attachment 9497599 [details] to obsolete.

Comment 12

[Pulsebot]

Pushed by [e-mail]:
https://github.com/mozilla-firefox/firefox/commit/2f19e759a8bd
https://hg.mozilla.org/integration/autoland/rev/cae1ad7408cb
pt 1. Changes to PHC pointer tests r=glandium
https://github.com/mozilla-firefox/firefox/commit/0f5c7ab77695
https://hg.mozilla.org/integration/autoland/rev/15dee2d249b6
pt 2. Use a custom array implementation for PHC's metadata r=glandium
https://github.com/mozilla-firefox/firefox/commit/d678b8623c01
https://hg.mozilla.org/integration/autoland/rev/4511e10cb420
pt 3. PHC's size is no-longer fixed at compile time r=glandium
https://github.com/mozilla-firefox/firefox/commit/8d63f4b9690a
https://hg.mozilla.org/integration/autoland/rev/6d53420157be
pt 4. Add support for growing PHC's storage r=glandium
https://github.com/mozilla-firefox/firefox/commit/0ce6f349085b
https://hg.mozilla.org/integration/autoland/rev/cd9cb17868e7
pt 5. Control PHC's size from a pref r=glandium

Comment 13

[agoloman]

https://hg.mozilla.org/mozilla-central/rev/cae1ad7408cb
https://hg.mozilla.org/mozilla-central/rev/15dee2d249b6
https://hg.mozilla.org/mozilla-central/rev/4511e10cb420
https://hg.mozilla.org/mozilla-central/rev/6d53420157be
https://hg.mozilla.org/mozilla-central/rev/cd9cb17868e7