Simplify handling of superpages in pmap_clear_modify()
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Authored by alc on Jul 22 2019, 3:19 PM.

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kib
markj
manu

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rS350335: Simplify the handling of superpages in pmap_clear_modify(). Specifically,

Summary

If a demotion succeeds, then all of the 4KB page mappings within the superpage-sized region must be valid, so there is no point in testing the validity of the 4KB page mapping that is going to be write protected.

Deindent the code.

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rS FreeBSD src repository - subversion

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alc created this revision.Jul 22 2019, 3:19 PM

Herald added subscribers: emaste, andrew. · View Herald TranscriptJul 22 2019, 3:19 PM

Peter, could you please test this patch on amd64 and i386.

Sure, happy to.

I finished the full stress2 tests on amd64 without any issues.

On i386 I ran into this problem, which seems unrelated to me. Unfortunately I did not get a dump as the debugger was looping.
I made a short attempt to recreate the problem, but without any luck.
Here's the partial console log: https://people.freebsd.org/~pho/stress/log/alc010.txt
I still need to run 170 tests on i386 to complete a full test.

In D21027#456866, @pho wrote:

I finished the full stress2 tests on amd64 without any issues.

Thank you.

On i386 I ran into this problem, which seems unrelated to me. Unfortunately I did not get a dump as the debugger was looping.
I made a short attempt to recreate the problem, but without any luck.
Here's the partial console log: https://people.freebsd.org/~pho/stress/log/alc010.txt
I still need to run 170 tests on i386 to complete a full test.

I agree that that problem seems unrelated.

The i386 tests finished with one further problem and an incomplete report: https://people.freebsd.org/~pho/stress/log/alc011.txt

In D21027#457081, @pho wrote:

The i386 tests finished with one further problem and an incomplete report: https://people.freebsd.org/~pho/stress/log/alc011.txt

That also seems unrelated. Thanks.

alc added reviewers: kib, markj.Jul 25 2019, 4:57 AM

kib accepted this revision.Jul 25 2019, 7:26 AM

This revision is now accepted and ready to land.Jul 25 2019, 7:26 AM

markj accepted this revision.Jul 25 2019, 3:30 PM

Closed by commit rS350335: Simplify the handling of superpages in pmap_clear_modify(). Specifically, (authored by alc). · Explain WhyJul 25 2019, 10:03 PM

This revision was automatically updated to reflect the committed changes.

alc added a commit: rS350335: Simplify the handling of superpages in pmap_clear_modify(). Specifically,.

Herald added a reviewer: manu. · View Herald TranscriptJul 25 2019, 10:03 PM

Herald added a subscriber: imp. · View Herald Transcript

hi,
I stopped by this code review while I was troubleshooting things for PR 242137.

as far as we understood, the issue I reported on that bug happens only if I use a particular hardware, but others may also be affected (not sure though).

should some of you guys can drop a quick look on that PR would be awesome; I'm pretty much interested on getting a better picture of all that.

In D21027#506785, @egypcio wrote:

hi,
I stopped by this code review while I was troubleshooting things for PR 242137.

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242137#c106

https://bugs.freebsd.org/bugzilla/show_bug.cgi?id=242137#c121 (*)

as far as we understood, the issue I reported on that bug happens only if I use a particular hardware, but others may also be affected (not sure though).

should some of you guys can drop a quick look on that PR would be awesome; I'm pretty much interested on getting a better picture of all that.

The thread in that PR is quite long and hard to understand. Can you provide a brief summary? From comment 126 it sounds like you are able to trigger some ntpd problem when both r352517 and r352519 are applied, but not when either commit is reverted?