vm_phys_early_alloc(): Prefer allocation at boundaries by default
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Authored by olce on Jan 23 2025, 5:16 PM.

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markj
dougm
alc

Summary

This is in preparation for a revamp of vm_page_startup() that will try
to allocate early memory at boundaries in order to reduce the span of
physical addresses to cover in the VM_PHYSSEG_DENSE model.

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Repository

rG FreeBSD src repository

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Buildable 61938
Build 58822: arc lint + arc unit

Event Timeline

olce created this revision.Jan 23 2025, 5:16 PM

Herald added a subscriber: imp. · View Herald TranscriptJan 23 2025, 5:16 PM

olce requested review of this revision.Jan 23 2025, 5:16 PM

Harbormaster completed remote builds in B61938: Diff 149795.Jan 23 2025, 5:16 PM

olce added a parent revision: D48638: vm_phys_early_alloc_ex*(): Introduce VM_PHYS_EAF_ADDR_BOUNDARIES_FIRST.Jan 23 2025, 5:21 PM

olce added a child revision: D48640: vm_page_startup(): Save memory in more cases on VM_PHYSSEG_DENSE.

I think it makes sense to revise this change to be conditional on VM_PHYSSEG_DENSE (and on the condition: vm_domains == 1 or PMAP_HAS_PAGE_ARRAY absent) in order to avoid disabling the anti-fragmentation mechanism on VM_PHYSSEG_SPARSE.

Impacts of parent revisions' changes.

Harbormaster completed remote builds in B62309: Diff 150706.Feb 7 2025, 8:06 PM

In D48639#1109239, @olce wrote:

I think it makes sense to revise this change to be conditional on VM_PHYSSEG_DENSE (and on the condition: vm_domains == 1 or PMAP_HAS_PAGE_ARRAY absent) in order to avoid disabling the anti-fragmentation mechanism on VM_PHYSSEG_SPARSE.

In the end not needed, as I changed the policy of allocation at boundaries to have a similar anti-fragmentation mechanism (see D48365).

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sys/

vm/

vm_phys.c

8 lines

Diff 149795

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vm_phys_early_alloc(): Prefer allocation at boundaries by defaultNeeds ReviewPublicActions