[OpenJDK 2D-Dev] RFR: 8240654 : ZGC can cause severe UI application repaint issues

[Jayathirth D v]

Hi Phil,

I tried tested the fix in my Windows 10 machine with Intel integrated UHD Graphics 620.

LargeWindowPaintTest.java passes with/without fix in my machine.
AlphaPrintTest.java without fix just opens up blank frame without any instructions and with fix it shows instructions for the test.
Is this expected behaviour?

AlphaPrintTest.java with fix when it shows instructions if I click on Pass(Since I don’t have printer right now) it doesn’t pass/close the window. Only after I click on Print button and then close print dialog it allows me to click on Pass button.

Also how does these tests behave in our internal CI machines?

Thanks,
Jay

> On 11-Jun-2020, at 2:18 AM, Philip Race <philip.race at oracle.com> wrote:
> 
> Bug: https://bugs.openjdk.java.net/browse/JDK-8240654 <https://bugs.openjdk.java.net/browse/JDK-8240654>
> Webrev: http://cr.openjdk.java.net/~prr/8240654/index.html <http://cr.openjdk.java.net/~prr/8240654/index.html>
> 
> This is for JDK 15 so review ASAP please since RDP 1 and the test cycle are looming.
> 
> This is not a fix for a JDK bug. It is a bunch of workarounds for a Microsoft Windows bug affecting
> GDI in the context of ZGC (http://openjdk.java.net/jeps/333 <http://openjdk.java.net/jeps/333>).
> Some extra details about the Windows bug at the end, but first the technical details of the fix.
> 
> With ZGC's memory allocation requirement of reserving memory in 2Mb chunks  some Windows GDI
> functions, mostly involving some bitmaps APIs may return a failure code (ie fail!)
> This typically occurs when Java heap memory is used for a Java image and then in a JNI
> call we use GetPrimitiveArrayCritical so that Java heap allocated memory is passed to a GDI
> function AND the Java heap memory spans one of the 2Mb boundaries. 
> This is very easy to trigger in almost any Java UI app if the window is of a large enough (ie typical) size.
> NB: if you have an Nvidia or ATI card, then you won't see it, because the D3D pipeline doesn't
> call the affected method but if you have an Intel chip as do 90% (?) of laptops you will see it.
> There are also several other places we found that are affected. Printing is the other one
> somewhat easy to trigger. The others : custom cursors and tray icons are less common.
> The painful thing here is that there is no definitive list (a list of the known ones is below) of
> affected Windows GDI APIs and we are just hunting around our code trying to see where it
> might be side-swiped by this bug.
> 
> The basic approach in these workarounds is that for cases where performance does not matter we now copy 
> and for cases where performance does matter or larger amounts of memory is involved we check if
> the return value of the GDI function indicates failure and then re-try with a copy of the heap memory. 
> Unless GDI was randomly failing already (unlikely) this should be a no-risk solution in the high profile cases. 
> We have done performance measurements on the important screen case and the failures
> happen fast so the penalty is then in the re-try which is only if ZGC is enabled.
> Always copying the memory is slower (and memcpy is the slow operation) than an alternative approach
> that "knows" about the memory allocation of ZGC but this coupling and the complexity seem like they aren't
> worth it since I haven't seen any visible performance consequence. That can be revisited
> some day if need be, but for now we have correctness which is the key as well as sufficient performance.
> 
> I've created an automated test for the most important on-screen case. 
> Also a manual printing test case which invokes ZGC is provided since there we also only
> conditionally copy. In the other cases we now always copy so existing test cases should over those.
> 
> There is some clean up in this fix - one completely unused  (provably so because it was #if'd out)
> JNI method in awt_PrintJob.cpp is removed since it had code that looked like it needed a workaround,
> which would be somewhat of a waste of effort.
> 
> the doPrintBand code and its callee bitsToDevice has code I think we can remove too since
> I don't see how it ever gets executed (the top down case for browserPrint == true) but
> I think I'll save that for a P4 follow-on since it does nothing that would be affected by this
> Windows bug.
> 
> One oddity is the in the printing case I observed that some times the rendering is performed
> even if an error code is returned. I don't know why, but in code we can't tell that it was actually
> rendered and in any case there is no harm in repeating the call with copied memory.
> 
> We are right before the JDK15 stabilisation fork and this fix needs to go there and will
> but the webrev is against jdk/client simply because jdk15 does not exist yet !
> 
> Please test and review ASAP.
> 
> About the bug:
> Microsoft has acknowleged the bug and will publish a knowledge base article about it
> but a fix may show up only in a future version of Windows. Not, it seems, any time soon.
> Below is a list of potentially affected GDI APIs. Per microsoft whether it actually manifests in
> any specific case depends on "branching"
> https://docs.microsoft.com/en-us/previous-versions/windows/desktop/wcs/checkbitmapbits <https://docs.microsoft.com/en-us/previous-versions/windows/desktop/wcs/checkbitmapbits>
> https://docs.microsoft.com/en-us/previous-versions/windows/desktop/wcs/createcolortransform <https://docs.microsoft.com/en-us/previous-versions/windows/desktop/wcs/createcolortransform>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-setdibitstodevice <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-setdibitstodevice>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-stretchdibits <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-stretchdibits>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-getbitmapbits <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-getbitmapbits>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-createdibitmap <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-createdibitmap>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-createdibsection <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-createdibsection>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-polydraw <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-polydraw>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-drawescape <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-drawescape>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-createbitmap <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-createbitmap>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-setbitmapbits <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-setbitmapbits>
> https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-getdibits <https://docs.microsoft.com/en-us/windows/win32/api/wingdi/nf-wingdi-getdibits>
> 
> -phil.
> 

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