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

Thu Jun 11 08:58:32 UTC 2020

Typo : I tried tested -> I tried testing

> On 11-Jun-2020, at 2:27 PM, Jayathirth D v <JAYATHIRTH.D.V at ORACLE.COM> wrote:
> 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 <mailto: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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