15810 - [Perf] PR_Sync is called when you close a read-only file

Status: RESOLVED FIXED

(Core :: XPCOM, defect, P3)

Description

[Simon Fraser [no longer active]]

FileImpl doesn't seem to be optimized for read-only files; it allocates an
mOutputbuffer, even if the file is opened in PR_RDONLY mode.

But a larger problem is that it calls Flush(), which calls PR_Sync, even if the
file is read-only. This will cause a lot more disk-rattling than is necessary.

Comment 1

[Simon Fraser [no longer active]]

Here's a diff for the flush fix:

Index: nsIFileStream.cpp
===================================================================
RCS file: /cvsroot/mozilla/xpcom/io/nsIFileStream.cpp,v
retrieving revision 3.26
diff -r3.26 nsIFileStream.cpp
388c388,389
<     Flush();
---
>     if (mNSPRMode & PR_RDONLY)
>         Flush();

Comment 2

[Simon Fraser [no longer active]]

Since we can't tell in the ctor whether the FileImp will be used in read or write
mode, I suggest we allocate the buffers lazily when we know we're writing.

Comment 3

[Simon Fraser [no longer active]]

Sorry that diff was wrong. Try this:

Index: nsIFileStream.cpp
===================================================================
RCS file: /cvsroot/mozilla/xpcom/io/nsIFileStream.cpp,v
retrieving revision 3.26
diff -r3.26 nsIFileStream.cpp
388c388,389
<     Flush();
---
>     if ((mNSPRMode & PR_RDONLY) == 0)
>         Flush();

Comment 4

[Doug Turner (:dougt)]

finders keeper.  can you check this diff in?

Comment 5

[Simon Fraser [no longer active]]

Fix in hand.

Comment 6

[rubydoo123]

since Simon has fix in hand, setting to M11

Comment 7

[Simon Fraser [no longer active]]

Fixed was checked in way back when.

Comment 8

[Erik]

*** Bug 209650 has been marked as a duplicate of this bug. ***