[Webkit-unassigned] [Bug 136478] Initialize m_usesNetworkProcess earlier in WebProcess::initializeWebProcess()

[bugzilla-daemon at webkit.org]

https://bugs.webkit.org/show_bug.cgi?id=136478


Alexey Proskuryakov <ap at webkit.org> changed:

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 Attachment #237552|review+                     |review-
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--- Comment #6 from Alexey Proskuryakov <ap at webkit.org>  2014-09-03 10:09:50 PST ---
(From update of attachment 237552)
I needed to check Mac code, and now that I've done that, it looks like this patch breaks Mac.

What happens is that in platformInitializeWebProcess(), we make WebProcess use the same on-disk cache that UI process and NetworkProcess use. There is some sad history of mistakes there - we had code that seemed like it made us use a different code path, but it didn't because m_usesNetworkProcess was not initialized yet. The code was mistakenly changed to actually respect the network process setting in <http://trac.webkit.org/changeset/170155>, and then we started to hit sandbox violations accessing the wrong cache. Then in <http://trac.webkit.org/r171156> I reverted the behavior, removing the broken usesNetworkProcess() check. I forgot to remove a comment saying that we wanted a standalone cache.

After platformInitializeWebProcess(), initializeWebProcess() calls setCacheModel(), which calls platformSetCacheModel(), which once again checks usesNetworkProcess() and disables the cache. This is also currently dead code, because m_usesNetworkProcess is still not initialized. But after this proposed patch, m_usesNetworkProcess will be true, so we will disable the shared disk cache in all processes!

Here is what I think needs to be done to fix the patch:

1. Remove this dead code from WebProcessCocoa.mm:

    // FIXME: Once there is no loading being done in the WebProcess, we should remove this,
    // as calling [NSURLCache sharedURLCache] initializes the cache, which we would rather not do.
    if (usesNetworkProcess()) {
        [nsurlCache setMemoryCapacity:0];
        [nsurlCache setDiskCapacity:0];
        return;
    }

2. Remove this comment from the same file:

    // When the network process is enabled, each web process wants a stand-alone
    // NSURLCache, which it can disable to save memory.

3. Notify Apple folks working on WebKit performance that the optimization to disable caching in WebProcess has been broken for a long time, and that we are removing what remains of that code (I will do it).

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