Allocate the vm_page_array on domain correct memory.
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Authored by jeff on Aug 13 2019, 5:41 PM.

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Reviewers

alc
kib
markj
gallatin

Commits

rS351555: vfs: stop passing LK_INTERLOCK to VOP_UNLOCK
rS351198: Allocate amd64's page array using pages and page directory pages from the

Summary

This gives us lower latency and lower interconnect bandwidth on many benchmarks that process a lot of pages. We probably should also affinitize the vm threads after this for maximum benefit.

I used a separate pml4 entry because it made life easier for me. There isn't a strong technical reason to do so. Given that the page array is 3% of memory I don't think this is an unreasonable use. There is a small downside that you can't skip allocating pages for the page array since it is not at the very end of memory anymore. This creates a waste of 3% of 3%. or .1% of memory. I find this acceptable.

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Repository

rS FreeBSD src repository - subversion

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Event Timeline

jeff created this revision.Aug 13 2019, 5:41 PM

Harbormaster completed remote builds in B25848: Diff 60748.Aug 13 2019, 5:41 PM

jeff edited the summary of this revision. (Show Details)Aug 13 2019, 5:47 PM

jeff added reviewers: alc, kib, markj, gallatin.

jeff mentioned this in D21250: Move phys_avail and dump_avail into MI code..Aug 13 2019, 5:53 PM

I suspect the diff generation missed vm_phys.c.

sys/amd64/amd64/pmap.c
1436 ↗	(On Diff #60748)	spaces around '/'
1439 ↗	(On Diff #60748)	and there
1593 ↗	(On Diff #60748)	you probably can set pg_nx there.
sys/vm/vm_reserv.c
1368 ↗	(On Diff #60748)	Put {} around the loop body, it has more than one line.
1372 ↗	(On Diff #60748)	And there too.

kib added inline comments.Aug 17 2019, 8:44 AM

sys/amd64/include/pmap.h
230 ↗	(On Diff #60748)	So the page array pml4 entry is just below DMAP, am I right ? And the large map max size is reduced by 512G ? You should update the map in amd64/include/vmparam.h under the comment 'Virtual addresses of things'.
237 ↗	(On Diff #60748)	This is strange, this line should be shown as changed. Do you have some issue with the patch generation ?

Address review feedback. Move the page array between the direct map and kva.

Harbormaster completed remote builds in B25941: Diff 60959.Aug 18 2019, 8:32 AM

jeff added inline comments.Aug 18 2019, 8:35 AM

sys/amd64/include/pmap.h
230 ↗	(On Diff #60748)	After this comment I decided to move it down and make sure it had a guard region on either side. There was a gap between KPML4BASE and DMPML4I that was just big enough. If direct map must be naturally aligned then when it doubles there will still be space even if kva doubles. I verified the vmparam.h values with gdb.