Bug 207807 – REGRESSION(r256633): 4% memory regression in new Membuster, possibly some leaking in WebKit Malloc? (Requested by yusukesuzuki on #webkit).

• Component: New Bugs
• Status: RESOLVED FIXED

[WebKit Commit Bot]

https://trac.webkit.org/changeset/256633 broke the build:
4% memory regression in new Membuster, possibly some leaking in WebKit Malloc? (Requested by yusukesuzuki on #webkit).

This is an automatic bug report generated by webkitbot. If this bug
report was created because of a flaky test, please file a bug for the flaky
test (if we don't already have one on file) and dup this bug against that bug
so that we can track how often these flaky tests fail.

[WebKit Commit Bot]

Created attachment 390856 [details]
ROLLOUT of r256633

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[WebKit Commit Bot]

Comment on attachment 390856 [details]
ROLLOUT of r256633

Clearing flags on attachment: 390856

Committed r256700: <https://trac.webkit.org/changeset/256700>

[WebKit Commit Bot]

All reviewed patches have been landed.  Closing bug.

[Radar WebKit Bug Importer]

<rdar://problem/59483218>

[Christopher Reid]

Created attachment 390861 [details]
Potential fix

These are the changes isolated for mac and a potential fix.

I believe the cause of the memory regression was because the file descriptor for the mapping was only opened with O_WRONLY and not O_RDWR which caused the mmap calls to fail on mac with EPERM.
The memory regression was likely resources stored in memory that were previously in a mapped file.

I added FileOpenMode::ReadWrite to match the flags from before that patch `O_RDWR | O_CREAT | O_EXCL`.

[Yusuke Suzuki]

(In reply to Christopher Reid from comment #5)
> Created attachment 390861 [details]
> Potential fix
> 
> These are the changes isolated for mac and a potential fix.
> 
> I believe the cause of the memory regression was because the file descriptor
> for the mapping was only opened with O_WRONLY and not O_RDWR which caused
> the mmap calls to fail on mac with EPERM.
> The memory regression was likely resources stored in memory that were
> previously in a mapped file.
> 
> I added FileOpenMode::ReadWrite to match the flags from before that patch
> `O_RDWR | O_CREAT | O_EXCL`.

I'm building Safari and running new Membuster to ensure this patch fixes the issue.