711881 - nsXMLHttpRequest::Send defeats DEFER_OPEN optimization for file streams by calling Available on the main thread

Status: NEW

(Core :: DOM: Core & HTML, defect, P3)

Description

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

XHR.send calls Available on the postdata stream, and if the page does xhr.send(file) that results in statting the file on the main thread.

Comment 1

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

I think the solution is to have XHR get the size from the File object, and then handle the sync i/o problems in the DOM file code.

Comment 2

[Nathan Froyd [:froydnj]]

Is this for the nsIInputStream case here:

http://mxr.mozilla.org/mozilla-central/source/content/base/src/nsXMLHttpRequest.cpp#2500

?  I don't see where you're suggesting to get the file object from.  It looks like the stream is always opened before providing it to send().

Comment 3

[Kyle Huey (Exited; not receiving bugmail, old account, do not use)]

I don't know if this bug is still relevant.  This code has changed a lot in the last 15 months.

Comment 4

[Josh Matthews [:jdm]]

GetResponseBody for an nsIInputStream still calls Available on the main thread.

Comment 5

[Thomas Wisniewski]

Is this still relevant? I see no reference to Available() in dom/xhr anymore, and dom/fetch seems to only call Available() in FetchStream::OnInputStreamReady.

Comment 6

[Josh Matthews [:jdm]]

There's a call to Available in https://dxr.mozilla.org/mozilla-central/source/netwerk/protocol/http/HttpBaseChannel.cpp#1017 which is invoked from InitiateFech (https://dxr.mozilla.org/mozilla-central/rev/7e962631ba4298bcefa571008661983d77c3e652/dom/xhr/XMLHttpRequestMainThread.cpp#2631). It's not clear to me whether that actually invokes the kind of behaviour that we are concerned about, though.