RFR(M): 8216060: [PPC64] Vector CRC implementation should be used by interpreter and be faster for short arrays
Gustavo Romero
gromero at linux.vnet.ibm.com
Fri Jan 4 18:54:32 UTC 2019
Hi Martin,
On 01/04/2019 02:13 PM, Doerr, Martin wrote:
> Hi Gustavo,
>
> when called from the interpreter (the scenario you observed), R21 is set before resizing the frame to avoid wasted stack space (InterpreterMacroAssembler::call_from_interpreter).
Got it. Thanks a lot for the explanations.
I think it doesn't currently matter in practice, but I'm wondering if to be
consistent we should cut back the stack back earlier also in
TemplateInterpreterGenerator::generate_CRC32_update_entry()?
diff -r a35f8c35d8c9 src/hotspot/cpu/ppc/templateInterpreterGenerator_ppc.cpp
--- a/src/hotspot/cpu/ppc/templateInterpreterGenerator_ppc.cpp Fri Jan 04 10:09:00 2019 +0100
+++ b/src/hotspot/cpu/ppc/templateInterpreterGenerator_ppc.cpp Fri Jan 04 13:44:37 2019 -0500
@@ -1840,11 +1840,12 @@
#endif
__ lwz(crc, 2*wordSize, argP); // Current crc state, zero extend to 64 bit to have a clean register.
+ // Restore caller sp for c2i case and return.
+ __ mr(R1_SP, R21_sender_SP); // Cut the stack back to where the caller started.
+
StubRoutines::ppc64::generate_load_crc_table_addr(_masm, table);
__ kernel_crc32_singleByte(crc, data, dataLen, table, tmp, true);
- // Restore caller sp for c2i case and return.
- __ mr(R1_SP, R21_sender_SP); // Cut the stack back to where the caller started.
__ blr();
// Generate a vanilla native entry as the slow path.
Currently there is no issue probably because generated code is simpler and does
no spills.
Best regards,
Gustavo
> When called from compiled methods, R21 is set by a c2i adapter which extends the compiled frame by space for arguments (gen_c2i_adapter).
>
> "mr(R1_SP, R21_sender_SP)" is more error-prone than "resize_frame_absolute" so I think the latter would be better (though it takes more registers and instructions), but I don't want to replace that as part of this CRC change.
>
> Best regards,
> Martin
>
>
> -----Original Message-----
> From: Gustavo Romero <gromero at linux.vnet.ibm.com>
> Sent: Freitag, 4. Januar 2019 14:44
> To: Doerr, Martin <martin.doerr at sap.com>; 'hotspot-compiler-dev at openjdk.java.net' <hotspot-compiler-dev at openjdk.java.net>
> Subject: Re: RFR(M): 8216060: [PPC64] Vector CRC implementation should be used by interpreter and be faster for short arrays
>
> Hi Martin,
>
> On 01/04/2019 07:30 AM, Doerr, Martin wrote:
>> thank you very much for confirming. This makes sense. We use different frame headers depending on whether the frame is the top Java frame or not (and on whether it's a debug build or not). Setting R1_SP to sender_SP is a shortcut for leaf calls which relies on having an unmodified stack until this point. So the patch fixes the issue.
>
> Glad to help! Thanks for the additional information, I was not aware that the
> selection of different frame headers could be done at compile time. One last
> question only for my education: what exactly advanced (incremented) R1_SP so it
> has to be cut back using sender_SP value, i.e. sender_SP tracks the frame for
> which function exactly or "who" is the caller exactly here?
>
> Thank you.
>
> Best regards,
> Gustavo
>
>> New webrev:
>> http://cr.openjdk.java.net/~mdoerr/8216060_PPC64_CRC/webrev.01/
>>
>> Best regards,
>> Martin
>>
>>
>> -----Original Message-----
>> From: Gustavo Romero <gromero at linux.vnet.ibm.com>
>> Sent: Donnerstag, 3. Januar 2019 19:36
>> To: Doerr, Martin <martin.doerr at sap.com>; 'hotspot-compiler-dev at openjdk.java.net' <hotspot-compiler-dev at openjdk.java.net>
>> Subject: Re: RFR(M): 8216060: [PPC64] Vector CRC implementation should be used by interpreter and be faster for short arrays
>>
>> Hi Martin,
>>
>> On 01/03/2019 03:34 PM, Doerr, Martin wrote:
>>> Unfortunately, I can't reproduce the crash. TestCRC32C works stable on our machine (with fastdbg build).
>>> I guess that the frameless spills mess up the stack. Can you check if the patch below helps?
>>
>> Thanks for providing a fix so I can try it.
>> Yes, I confirm the patch below indeed fixes the sigsegv crash when CRC32C update() method is used.
>> I also confirm that I don't observe the crash on the fastdebug build, only on the release build.
>> It also only affects the Interpreter mode, so passing -Xcomp avoids the crash on the release build.
>>
>> Just as reference, I can reproduce it on the release build with the following trivial code:
>>
>> import java.util.zip.CRC32C;
>>
>> class CRC32C_v1 {
>> public static void main(String[] arg) {
>> byte[] b = new byte[1024];
>>
>> CRC32C crc32c = new CRC32C();
>> crc32c.update(b, 0, b.length);
>>
>> System.out.println(crc32c.getValue());
>> }
>> }
>>
>> Thanks for fixing the typos.
>>
>>
>> Best regards,
>> Gustavo
>>
>>> Best regards,
>>> Martin
>>>
>>>
>>> diff -r a33f49d5998c src/hotspot/cpu/ppc/templateInterpreterGenerator_ppc.cpp
>>> --- a/src/hotspot/cpu/ppc/templateInterpreterGenerator_ppc.cpp Thu Jan 03 17:30:03 2019 +0100
>>> +++ b/src/hotspot/cpu/ppc/templateInterpreterGenerator_ppc.cpp Thu Jan 03 18:33:16 2019 +0100
>>> @@ -1924,6 +1924,9 @@
>>> __ addi(data, data, arrayOopDesc::base_offset_in_bytes(T_BYTE));
>>> }
>>>
>>> + // Restore caller sp for c2i case.
>>> + __ mr(R1_SP, R21_sender_SP); // Cut the stack back to where the caller started.
>>> +
>>> StubRoutines::ppc64::generate_load_crc_table_addr(_masm, table);
>>>
>>> if (!VM_Version::has_vpmsumb()) {
>>> @@ -1933,8 +1936,6 @@
>>> __ kernel_crc32_vpmsum(crc, data, dataLen, table, t0, t1, t2, t3, tc0, tc1, tc2, true);
>>> }
>>>
>>> - // Restore caller sp for c2i case and return.
>>> - __ mr(R1_SP, R21_sender_SP); // Cut the stack back to where the caller started.
>>> __ blr();
>>>
>>> // Generate a vanilla native entry as the slow path.
>>> @@ -2014,6 +2015,9 @@
>>> __ addi(data, data, arrayOopDesc::base_offset_in_bytes(T_BYTE));
>>> }
>>>
>>> + // Restore caller sp for c2i case.
>>> + __ mr(R1_SP, R21_sender_SP); // Cut the stack back to where the caller started.
>>> +
>>> StubRoutines::ppc64::generate_load_crc32c_table_addr(_masm, table);
>>>
>>> if (!VM_Version::has_vpmsumb()) {
>>> @@ -2023,8 +2027,6 @@
>>> __ kernel_crc32_vpmsum(crc, data, dataLen, table, t0, t1, t2, t3, tc0, tc1, tc2, false);
>>> }
>>>
>>> - // Restore caller sp for c2i case and return.
>>> - __ mr(R1_SP, R21_sender_SP); // Cut the stack back to where the caller started.
>>> __ blr();
>>>
>>> BLOCK_COMMENT("} CRC32C_update{Bytes|DirectByteBuffer}");
>>>
>>>
>>> -----Original Message-----
>>> From: Gustavo Romero <gromero at linux.vnet.ibm.com>
>>> Sent: Donnerstag, 3. Januar 2019 17:13
>>> To: Doerr, Martin <martin.doerr at sap.com>; 'hotspot-compiler-dev at openjdk.java.net' <hotspot-compiler-dev at openjdk.java.net>
>>> Subject: Re: RFR(M): 8216060: [PPC64] Vector CRC implementation should be used by interpreter and be faster for short arrays
>>>
>>> Hi Martin,
>>>
>>> oh that's nice. You removed the 512-byte block constraint and also wired it up to the Interpreter :)
>>>
>>> For the worst case, unaligned 512 byte array, I see the gap to aligned 512 byte array reduced by about ~5.7x.
>>>
>>> On the Interpreter I see an improvement of at least 50% for 1024 bytes.
>>>
>>> This is all for the CRC32 class.
>>>
>>> On CRC32C I'm getting a SIGSEV that can be reproduced running against ./test/hotspot/jtreg/compiler/intrinsics/zip/TestCRC32C.java.
>>>
>>> I've upload a full log into http://cr.openjdk.java.net/~gromero/logs/crc32c_sigsegv/
>>>
>>> I'm leaving for the lunch and I'll take a closer look when back. But probably you will figure it out before I sit to appreciate the meal :)
>>>
>>> Finally, since the change does some cleanup, I wonder if it would be worth fixing the following typos:
>>>
>>> I think it's Barrett const., not Barret. Probably 'barret' is used in the code as a short version
>>> for Barrett but it should be changed in
>>>
>>> + // Point to Barret constants
>>> + add_const_optimized(cur_const, constants, outer_consts_size + inner_consts_size);
>>> +
>>>
>>> ?
>>>
>>> s/not/note/ in:
>>> cpu/ppc/macroAssembler_ppc.cpp:3977:// A not on the lookup table address(es):
>>>
>>> d/lives/ in:
>>> cpu/ppc/macroAssembler_ppc.cpp:4265: mtvrwz(VCRC, crc); // crc lives lives in VCRC, now
>>>
>>> Best regards,
>>> Gustavo
>>>
>>> On 01/03/2019 12:17 PM, Doerr, Martin wrote:
>>>> Hi,
>>>>
>>>> the JVM on PPC64 currently misses usage of the fast vector implementation in the interpreter code.
>>>>
>>>> In addition, performance is not good for short arrays (unaligned 512 byte arrays or shorter arrays) because the current vector implementation needs at least 512 bytes.
>>>>
>>>> Bug:
>>>>
>>>> https://bugs.openjdk.java.net/browse/JDK-8216060
>>>>
>>>> I have addressed these 2 issues + some cleanup with the following webrev:
>>>>
>>>> http://cr.openjdk.java.net/~mdoerr/8216060_PPC64_CRC/webrev.00/ <http://cr.openjdk.java.net/%7Emdoerr/8216060_PPC64_CRC/webrev.00/>
>>>>
>>>> Please review.
>>>>
>>>> Best regards,
>>>>
>>>> Martin
>>>>
>>>
>>
>
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