115129 - stream loader optimizations

Status: RESOLVED FIXED

(Core :: Networking, defect, P3)

Description

[Darin Fisher]

noticed that nsStreamLoader does a couple things that could be improved:

1) nsStreamLoader::OnDataAvailable calls Read instead of ReadSegments on the
input stream, resulting in an extra buffer copy.

2) nsStreamLoader::OnDataAvailable simply appends to mData, which is a
nsCString.  I noticed that at startup there are a number of CSS and JS files for
which OnDataAvailable is called several times.  The result is several
reallocations of mData.  This can be avoided by preallocating mData in
OnStartRequest to a size equal to the expected content length.  This requires
modifications to the JAR channel since it does not expose the content length of
the JAR item.

I'm not sure how much of a performance cost these things are... my initial
evaluation under Linux didn't show much of an improvement.  I'm hoping that
Win2k will show otherwise.

Comment 1

[Darin Fisher]

Attachment: v1.0 patch

this patch gave me a 0.9% startup improvement, and a 0.5% page load improvement
on win2k.

Comment 2

[Darin Fisher]

gagan: can you r= this patch?

Comment 3

[Gagan]

Comment on attachment 61673 [details] [diff] [review]
v1.0 patch

WriteSegmentFun? :-) That the best you could come up with?... r=gagan

Comment 4

[Brendan Eich [:brendan]]

Comment on attachment 61673 [details] [diff] [review]
v1.0 patch

+    if (NS_SUCCEEDED(rv))
+	 (*aInputStream)->Available((PRUint32 *) &mContentLength);

Do we know that Available returns the jar member's content-length, always?

/be

Comment 5

[Darin Fisher]

brendan: yes... or at least that is how it is currently implemented.  available
returns the "real size" of the zip archive segment.

dveditz: can you double check this?

Comment 6

[Daniel Veditz [:dveditz]]

Available() will return what's left of the data in the jar member. Before the
first read this will always be the full uncompressed size of the member.

Comment 7

[Darin Fisher]

fixed-on-trunk

Comment 8

[Antonio.Xu]

I found when i add this patch,on my source,then build on solaris,my mozilla 
page loading speed change slower.so i suggest we should research it.

Comment 9

[Darin Fisher]

Antonio.Xu: what is your page load test?  this would only effect pages w/
external css or js files.