Allow allocation of pages from beyond the last max order block of a range
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Authored by dougm on Mar 31 2022, 7:13 AM.

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rG557dc337e6cb: vm_phys: check small blocks to finish allocation

Summary

In vm_phys_alloc_queues_contig, in the case that a sequence of max-order blocks are sought to fulfill an allocation, a sequence is ruled out if it does not have enough max-order blocks to satisfy the allocation. However, there may be smaller blocks of free memory that follow the last max-order block in the sequence, and they may be big enough complete the allocation request, so check for that possibility before giving up on that block sequence.

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rG FreeBSD src repository

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dougm requested review of this revision.Mar 31 2022, 7:13 AM

dougm created this revision.

This looks right to me.

sys/vm/vm_phys.c
1420	It would be helpful to have a comment explaining what this loop does.

This revision is now accepted and ready to land.Mar 31 2022, 3:56 PM

Add/edit comments only.

This revision now requires review to proceed.Mar 31 2022, 4:29 PM

markj added inline comments.Mar 31 2022, 4:45 PM

sys/vm/vm_phys.c
1409

Fix comment typo.

markj accepted this revision.Mar 31 2022, 4:58 PM

This revision is now accepted and ready to land.Mar 31 2022, 4:58 PM

I'm not sure how much testing is required for this patch.
I ran the three contigmalloc(9) tests I have in a loop for four hours. I followed up with a few hours of random stress2 tests.
No problems seen.

Closed by commit rG557dc337e6cb: vm_phys: check small blocks to finish allocation (authored by dougm). · Explain WhyMar 31 2022, 9:23 PM

This revision was automatically updated to reflect the committed changes.

dougm added a commit: rG557dc337e6cb: vm_phys: check small blocks to finish allocation.

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