RFR: 8303215: Make thread stacks not use huge pages

[Poonam Bajaj]

On Tue, 23 May 2023 18:39:17 GMT, Thomas Stuefe <stuefe at openjdk.org> wrote:

> Yes, this is a pragmatic workaround. I believe @theRealAph recommended the same solution.
> 
> Did you test this on an aarch64 kernel with 64k pages? I suspect the 2040 default size only works for 4k or 8k pages, for larger page sizes pthread_create would just round up the stack size again to 2MB.

This does not solve the problem when the default small page size is 64K. The stack size gets rounded up to 2048K.

JavaThread:

0000ffff18ff0000     192       0       0 -----   [ anon ]
0000ffff19020000    1856     192     192 rw---   [ anon ]
0000ffff191f0000     192       0       0 -----   [ anon ]
0000ffff19220000    1856     192     192 rw---   [ anon ]
0000ffff193f0000     192       0       0 -----   [ anon ]
0000ffff19420000    1856     192     192 rw---   [ anon ]

non-JavaThread:

0000ffff6c170000      64       0       0 -----   [ anon ]
0000ffff6c180000    2048      64      64 rw---   [ anon ]
0000ffff6c380000      64       0       0 -----   [ anon ]
0000ffff6c390000    2048      64      64 rw---   [ anon ]


For 64k page size, changing the stack size to 1920K (2048 - 2*64) would work:

0000fffdc5ba0000     192       0       0 -----   [ anon ]
0000fffdc5bd0000    1728     192     192 rw---   [ anon ]
0000fffdc5d80000     192       0       0 -----   [ anon ]
0000fffdc5db0000    1728     192     192 rw---   [ anon ]
0000fffdc5f60000     192       0       0 -----   [ anon ]
0000fffdc5f90000    1728     192     192 rw---   [ anon ]

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PR Comment: https://git.openjdk.org/jdk/pull/14105#issuecomment-1559959246