1850948 - Use lower level implementation for GetMemoryMappings, avoiding a buffer copy in the process

Status: RESOLVED FIXED

(Firefox Build System :: General, task)

Description

[[:sergesanspaille]]

The implementation of GetMemoryMappings uses an internal std::string to read each line, and that buffer is later copied to an nsAutoCStringN in order to perform an strtok-based parsing.

Using a lower level approach avoid the copy on each line processing, and avoid using an nsAutoCStringN that has an extra overhead under -ftrivial-auto-var-init (to initialize the stack buffer).

Comment 1

[[:sergesanspaille]]

Attachment: Bug 1850948 - Use std::string::data() as strtok param in GetMemoryMappings, avoiding a buffer copy in the process r=emilio!

This is both beneficial for the actual code and an enhancement wrt.
-ftrivial-auto-var-init as it gets rid of a usage of nsAutoCString.

Comment 2

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/d94f12d0e000
Use lower level implementation for GetMemoryMappings, avoiding a buffer copy in the process r=emilio

Comment 3

[Cosmin Sabou [:CosminS]]

Backed out for causing memory related assertion failures.

Push with failures: https://treeherder.mozilla.org/jobs?repo=autoland&resultStatus=pending%2Crunning%2Csuccess%2Ctestfailed%2Cbusted%2Cexception%2Cretry%2Cusercancel&searchStr=gv&fromchange=79fd00522da11013e2076ceccfd842c54d2f0822&tochange=f5e6bce28e5060c274360897d0241d38e2af632c&selectedTaskRun=KyxGwZhCQDmR4qp_g5rdTA.0

Failure log:

• https://treeherder.mozilla.org/logviewer?job_id=427594406&repo=autoland
• https://treeherder.mozilla.org/logviewer?job_id=427594419&repo=autoland

Backout link: https://hg.mozilla.org/integration/autoland/rev/f5e6bce28e5060c274360897d0241d38e2af632c

Comment 4

[[:sergesanspaille]]

Issue identified, I submitted a patch in patch 1851154

Comment 5

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/8b72bb550f87
Use lower level implementation for GetMemoryMappings, avoiding a buffer copy in the process r=emilio

Comment 6

[Sandor Molnar[:smolnar]]

Backed out for causing build bustage in xpcom/base/MemoryMapping.cpp

Backout link: https://hg.mozilla.org/integration/autoland/rev/272e977ff5ffe96d148f3b45c018078dc7b26d7d

Push with failures

Failure log -> ERROR - /builds/worker/checkouts/gecko/xpcom/base/MemoryMapping.cpp:125:10: error: use of undeclared identifier 'getline'; did you mean 'std::getline'?

Comment 7

[Pulsebot]

Pushed by [e-mail]:
https://hg.mozilla.org/integration/autoland/rev/2f21879d591e
Use std::string::data() as strtok param in GetMemoryMappings, avoiding a buffer copy in the process r=emilio

Comment 8

[Cristina Horotan [:chorotan]]

https://hg.mozilla.org/mozilla-central/rev/2f21879d591e