pc64: preallocate mmupool page tables

preallocate 2% of user pages for page tables and MMU structures
and keep them mapped in the VMAP range. this leaves more space
in the KZERO window and avoids running out of kernel memory on
machines with large amounts of memory.

1 files changed, 64 insertions, 1 deletions

diff --git a/sys/src/9/pc64/mmu.c b/sys/src/9/pc64/mmu.c
index 9261354e8..dfb165ef5 100644
--- a/sys/src/9/pc64/mmu.c
+++ b/sys/src/9/pc64/mmu.c
@@ -271,7 +271,11 @@ mmuwalk(uintptr* table, uintptr va, int level, int create)
 		if(pte & PTEVALID){
 			if(pte & PTESIZE)
 				return 0;
-			table = KADDR(PPN(pte));
+			pte = PPN(pte);
+			if(pte >= (uintptr)-KZERO)
+				table = (void*)(pte + VMAP);
+			else
+				table = (void*)(pte + KZERO);
 		} else {
 			if(!create)
 				return 0;
@@ -570,3 +574,62 @@ patwc(void *a, int n)
 		*pte = (*pte & ~mask) | (attr & mask);
 	}
 }
+
+/*
+ * The palloc.pages array and mmupool can be a large chunk
+ * out of the 2GB window above KZERO, so we allocate from
+ * upages and map in the VMAP window before pageinit()
+ */
+void
+preallocpages(void)
+{
+	Pallocmem *pm;
+	uintptr va, base, top;
+	vlong tsize, psize;
+	ulong np, nt;
+	int i;
+
+	np = 0;
+	for(i=0; i<nelem(palloc.mem); i++){
+		pm = &palloc.mem[i];
+		np += pm->npage;
+	}
+	nt = np / 50;	/* 2% for mmupool */
+	np -= nt;
+
+	nt = (uvlong)nt*BY2PG / (sizeof(MMU)+PTSZ);
+	tsize = (uvlong)nt * (sizeof(MMU)+PTSZ);
+
+	psize = (uvlong)np * BY2PG;
+	psize += sizeof(Page) + BY2PG;
+	psize = (psize / (sizeof(Page)+BY2PG)) * sizeof(Page);
+
+	psize += tsize;
+	psize = ROUND(psize, PGLSZ(1));
+
+	for(i=0; i<nelem(palloc.mem); i++){
+		pm = &palloc.mem[i];
+		base = ROUND(pm->base, PGLSZ(1));
+		top = pm->base + (uvlong)pm->npage * BY2PG;
+		if((base + psize) <= VMAPSIZE && (vlong)(top - base) >= psize){
+			pm->base = base + psize;
+			pm->npage = (top - pm->base)/BY2PG;
+
+			va = base + VMAP;
+			pmap(m->pml4, base | PTEGLOBAL|PTEWRITE|PTEVALID, va, psize);
+
+			palloc.pages = (void*)(va + tsize);
+
+			mmupool.nfree = mmupool.nalloc = nt;
+			mmupool.free = (void*)(va + (uvlong)nt*PTSZ);
+			for(i=0; i<nt; i++){
+				mmupool.free[i].page = (uintptr*)va;
+				mmupool.free[i].next = &mmupool.free[i+1];
+				va += PTSZ;
+			}
+			mmupool.free[i-1].next = nil;
+
+			break;
+		}
+	}
+}