One side-effect of dlg@'s "* 8" pool diff is that some pools now use
"large" pool pages that aren't directly mapped on PMAP_DIRECT
architecture. In general it's not possible to map "large" pages
directly since the individual memory pages are not guaranteed to be
contigious. However, the mbuf cluster pools use the kp_dma_contig
constraint, which does guarantee that the pages are contigious. The
diff below makes us use direct mappings for those pool pages. This
should make allocating/deallocating mbuf clusters faster and decrease
kva pressure on PMAP_DIRECT architecture.
In the process I deleted the disabled "dubious optimization" code.
Nobody picked this up in the last couple of years since art@ committed
this code.
ok?
P.S. I would not be surprised if this would "fix" the problems landisk
has with the "* 8" pool diff. Currently updating my landisk to
verify.
Index: uvm_km.c
===================================================================
RCS file: /home/cvs/src/sys/uvm/uvm_km.c,v
retrieving revision 1.123
diff -u -p -r1.123 uvm_km.c
--- uvm_km.c 17 Dec 2014 06:58:11 -0000 1.123
+++ uvm_km.c 28 Dec 2014 19:37:42 -0000
@@ -811,9 +811,6 @@ km_alloc(size_t sz, const struct kmem_va
vm_prot_t prot;
int pla_flags;
int pla_maxseg;
-#ifdef __HAVE_PMAP_DIRECT
- paddr_t pa;
-#endif
vaddr_t va, sva;
KASSERT(sz == round_page(sz));
@@ -841,33 +838,18 @@ km_alloc(size_t sz, const struct kmem_va
#ifdef __HAVE_PMAP_DIRECT
if (kv->kv_align)
goto alloc_va;
-#if 1
- /*
- * For now, only do DIRECT mappings for single page
- * allocations, until we figure out a good way to deal
- * with contig allocations in km_free.
- */
- if (!kv->kv_singlepage)
- goto alloc_va;
-#endif
+
/*
- * Dubious optimization. If we got a contig segment, just map it
- * through the direct map.
+ * Only use direct mappings for single page or single segment
+ * allocations.
*/
- TAILQ_FOREACH(pg, &pgl, pageq) {
- if (pg != TAILQ_FIRST(&pgl) &&
- VM_PAGE_TO_PHYS(pg) != pa + PAGE_SIZE)
- break;
- pa = VM_PAGE_TO_PHYS(pg);
- }
- if (pg == NULL) {
+ if (kv->kv_singlepage || kp->kp_maxseg == 1) {
TAILQ_FOREACH(pg, &pgl, pageq) {
- vaddr_t v;
- v = pmap_map_direct(pg);
+ va = pmap_map_direct(pg);
if (pg == TAILQ_FIRST(&pgl))
- va = v;
+ sva = va;
}
- return ((void *)va);
+ return ((void *)sva);
}
#endif
alloc_va:
@@ -947,28 +929,35 @@ km_free(void *v, size_t sz, const struct
struct vm_page *pg;
struct pglist pgl;
- sva = va = (vaddr_t)v;
- eva = va + sz;
+ sva = (vaddr_t)v;
+ eva = sva + sz;
- if (kp->kp_nomem) {
+ if (kp->kp_nomem)
goto free_va;
- }
- if (kv->kv_singlepage) {
#ifdef __HAVE_PMAP_DIRECT
- pg = pmap_unmap_direct(va);
- uvm_pagefree(pg);
+ if (kv->kv_singlepage || kp->kp_maxseg == 1) {
+ TAILQ_INIT(&pgl);
+ for (va = sva; va < eva; va += PAGE_SIZE) {
+ pg = pmap_unmap_direct(va);
+ TAILQ_INSERT_TAIL(&pgl, pg, pageq);
+ }
+ uvm_pglistfree(&pgl);
+ return;
+ }
#else
+ if (kv->kv_singlepage) {
struct uvm_km_free_page *fp = v;
+
mtx_enter(&uvm_km_pages.mtx);
fp->next = uvm_km_pages.freelist;
uvm_km_pages.freelist = fp;
if (uvm_km_pages.freelistlen++ > 16)
wakeup(&uvm_km_pages.km_proc);
mtx_leave(&uvm_km_pages.mtx);
-#endif
return;
}
+#endif
if (kp->kp_pageable) {
pmap_remove(pmap_kernel(), sva, eva);
