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[src/trunk]: src/sys/arch/aarch64 - free empty page tables pages if reach a c...



details:   https://anonhg.NetBSD.org/src/rev/1189fb30744a
branches:  trunk
changeset: 998141:1189fb30744a
user:      ryo <ryo%NetBSD.org@localhost>
date:      Mon Apr 08 21:18:22 2019 +0000

description:
- free empty page tables pages if reach a certain usage.
- need to lock at removing an old pg (_pmap_remove_pv) in _pmap_enter()

diffstat:

 sys/arch/aarch64/aarch64/pmap.c |  137 +++++++++++++++++++++++++++++++++------
 sys/arch/aarch64/include/asan.h |    4 +-
 sys/arch/aarch64/include/pmap.h |    5 +-
 3 files changed, 119 insertions(+), 27 deletions(-)

diffs (truncated from 321 to 300 lines):

diff -r 6102c95630ed -r 1189fb30744a sys/arch/aarch64/aarch64/pmap.c
--- a/sys/arch/aarch64/aarch64/pmap.c   Mon Apr 08 20:18:14 2019 +0000
+++ b/sys/arch/aarch64/aarch64/pmap.c   Mon Apr 08 21:18:22 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: pmap.c,v 1.39 2019/04/06 18:30:20 ryo Exp $    */
+/*     $NetBSD: pmap.c,v 1.40 2019/04/08 21:18:22 ryo Exp $    */
 
 /*
  * Copyright (c) 2017 Ryo Shimizu <ryo%nerv.org@localhost>
@@ -27,7 +27,7 @@
  */
 
 #include <sys/cdefs.h>
-__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.39 2019/04/06 18:30:20 ryo Exp $");
+__KERNEL_RCSID(0, "$NetBSD: pmap.c,v 1.40 2019/04/08 21:18:22 ryo Exp $");
 
 #include "opt_arm_debug.h"
 #include "opt_ddb.h"
@@ -194,6 +194,7 @@
 #define pv_next        pv_link.tqe_next
 
 #define L3INDEXMASK    (L3_SIZE * Ln_ENTRIES - 1)
+#define PDPSWEEP_TRIGGER       512
 
 void atomic_add_16(volatile uint16_t *, int16_t);
 uint16_t atomic_add_16_nv(volatile uint16_t *, int16_t);
@@ -439,6 +440,7 @@
        kpm = pmap_kernel();
        kpm->pm_asid = 0;
        kpm->pm_refcnt = 1;
+       kpm->pm_idlepdp = 0;
        kpm->pm_l0table = l0;
        kpm->pm_l0table_pa = l0pa;
        kpm->pm_activated = true;
@@ -564,7 +566,7 @@
 }
 
 paddr_t
-pmap_alloc_pdp(struct pmap *pm, struct vm_page **pgp, bool waitok)
+pmap_alloc_pdp(struct pmap *pm, struct vm_page **pgp, int flags, bool waitok)
 {
        paddr_t pa;
        struct vm_page *pg;
@@ -573,9 +575,10 @@
        UVMHIST_CALLED(pmaphist);
 
        if (uvm.page_init_done) {
+               int aflags = ((flags & PMAP_CANFAIL) ? 0 : UVM_PGA_USERESERVE) |
+                   UVM_PGA_ZERO;
  retry:
-               pg = uvm_pagealloc(NULL, 0, NULL,
-                   UVM_PGA_USERESERVE | UVM_PGA_ZERO);
+               pg = uvm_pagealloc(NULL, 0, NULL, aflags);
                if (pg == NULL) {
                        if (waitok) {
                                uvm_wait("pmap_alloc_pdp");
@@ -620,6 +623,61 @@
        PMAP_COUNT(pdp_free);
 }
 
+/* free empty page table pages */
+static int
+_pmap_sweep_pdp(struct pmap *pm)
+{
+       struct vm_page *pg, *tmp;
+       pd_entry_t *ptep_in_parent, opte;
+       paddr_t pa, pdppa;
+       int nsweep;
+       uint16_t wirecount;
+
+       nsweep = 0;
+       TAILQ_FOREACH_SAFE(pg, &pm->pm_vmlist, mdpage.mdpg_vmlist, tmp) {
+               if (pg->wire_count != 1)
+                       continue;
+
+               pa = VM_PAGE_TO_PHYS(pg);
+               if (pa == pm->pm_l0table_pa)
+                       continue;
+
+               ptep_in_parent = VM_PAGE_TO_MD(pg)->mdpg_ptep_parent;
+               if (ptep_in_parent == NULL) {
+                       /* no parent */
+                       pmap_free_pdp(pm, pg);
+                       nsweep++;
+                       continue;
+               }
+
+               /* unlink from parent */
+               opte = atomic_swap_64(ptep_in_parent, 0);
+               KASSERT(lxpde_valid(opte));
+               wirecount = atomic_add_16_nv(&pg->wire_count, -1); /* 1 -> 0 */
+               KASSERT(wirecount == 0);
+               pmap_free_pdp(pm, pg);
+               nsweep++;
+
+               /* L3->L2->L1. no need for L0 */
+               pdppa = AARCH64_KVA_TO_PA(trunc_page((vaddr_t)ptep_in_parent));
+               if (pdppa == pm->pm_l0table_pa)
+                       continue;
+
+               pg = PHYS_TO_VM_PAGE(pdppa);
+               KASSERT(pg != NULL);
+               KASSERTMSG(pg->wire_count >= 1,
+                   "wire_count=%d", pg->wire_count);
+               /* decrement wire_count of parent */
+               wirecount = atomic_add_16_nv(&pg->wire_count, -1);
+               KASSERTMSG(pg->wire_count <= (Ln_ENTRIES + 1),
+                   "pm=%p[%d], pg=%p, wire_count=%d",
+                   pm, pm->pm_asid, pg, pg->wire_count);
+       }
+       atomic_swap_uint(&pm->pm_idlepdp, 0);
+
+       return nsweep;
+}
+
 static void
 _pmap_free_pdp_all(struct pmap *pm)
 {
@@ -1270,11 +1328,12 @@
        pm = pool_cache_get(&_pmap_cache, PR_WAITOK);
        memset(pm, 0, sizeof(*pm));
        pm->pm_refcnt = 1;
+       pm->pm_idlepdp = 0;
        pm->pm_asid = -1;
        TAILQ_INIT(&pm->pm_vmlist);
        mutex_init(&pm->pm_lock, MUTEX_DEFAULT, IPL_VM);
 
-       pm->pm_l0table_pa = pmap_alloc_pdp(pm, NULL, true);
+       pm->pm_l0table_pa = pmap_alloc_pdp(pm, NULL, 0, true);
        KASSERT(pm->pm_l0table_pa != POOL_PADDR_INVALID);
        pm->pm_l0table = (pd_entry_t *)AARCH64_PA_TO_KVA(pm->pm_l0table_pa);
        KASSERT(((vaddr_t)pm->pm_l0table & (PAGE_SIZE - 1)) == 0);
@@ -1379,14 +1438,21 @@
 
        wirecount = atomic_add_16_nv(&pg->wire_count, -1);
 
-       if (!do_free_pdp)
+       if (!do_free_pdp) {
+               /*
+                * pm_idlepdp is counted by only pmap_page_protect() with
+                * VM_PROT_NONE. it is not correct because without considering
+                * pmap_enter(), but useful hint to just sweep.
+                */
+               if (wirecount == 1)
+                       atomic_inc_uint(&pm->pm_idlepdp);
                return false;
+       }
 
        /* if no reference, free pdp */
        removed = false;
        while (wirecount == 1) {
                pd_entry_t *ptep_in_parent, opte;;
-
                ptep_in_parent = VM_PAGE_TO_MD(pg)->mdpg_ptep_parent;
                if (ptep_in_parent == NULL) {
                        /* no parent */
@@ -1426,7 +1492,7 @@
 _pmap_enter(struct pmap *pm, vaddr_t va, paddr_t pa, vm_prot_t prot,
     u_int flags, bool kenter)
 {
-       struct vm_page *pg, *pdppg, *pdppg0;
+       struct vm_page *pg, *pgs[2], *pdppg, *pdppg0;
        struct pv_entry *spv, *opv = NULL;
        pd_entry_t pde;
        pt_entry_t attr, pte, opte, *ptep;
@@ -1493,6 +1559,13 @@
 
        pm_lock(pm);
 
+       if (pm->pm_idlepdp >= PDPSWEEP_TRIGGER) {
+               if (_pmap_sweep_pdp(pm) != 0) {
+                       /* several L1-L3 page table pages have been freed */
+                       aarch64_tlbi_by_asid(pm->pm_asid);
+               }
+       }
+
        /*
         * traverse L0 -> L1 -> L2 -> L3 table with growing pdp if needed.
         */
@@ -1502,7 +1575,7 @@
        pde = l0[idx];
        if (!l0pde_valid(pde)) {
                /* no need to increment L0 occupancy. L0 page never freed */
-               pdppa = pmap_alloc_pdp(pm, &pdppg, flags);      /* L1 pdp */
+               pdppa = pmap_alloc_pdp(pm, &pdppg, flags, false);  /* L1 pdp */
                if (pdppa == POOL_PADDR_INVALID) {
                        if (flags & PMAP_CANFAIL) {
                                error = ENOMEM;
@@ -1525,7 +1598,7 @@
        if (!l1pde_valid(pde)) {
                pdppa0 = pdppa;
                pdppg0 = pdppg;
-               pdppa = pmap_alloc_pdp(pm, &pdppg, flags);      /* L2 pdp */
+               pdppa = pmap_alloc_pdp(pm, &pdppg, flags, false);  /* L2 pdp */
                if (pdppa == POOL_PADDR_INVALID) {
                        if (flags & PMAP_CANFAIL) {
                                error = ENOMEM;
@@ -1549,7 +1622,7 @@
        if (!l2pde_valid(pde)) {
                pdppa0 = pdppa;
                pdppg0 = pdppg;
-               pdppa = pmap_alloc_pdp(pm, &pdppg, flags);      /* L3 pdp */
+               pdppa = pmap_alloc_pdp(pm, &pdppg, flags, false);  /* L3 pdp */
                if (pdppa == POOL_PADDR_INVALID) {
                        if (flags & PMAP_CANFAIL) {
                                error = ENOMEM;
@@ -1580,8 +1653,9 @@
        }
 #endif
 
-       if (pg != NULL)
-               pmap_pv_lock(VM_PAGE_TO_MD(pg));
+       /* for lock ordering for pg and opg */
+       pgs[0] = pg;
+       pgs[1] = NULL;
 
        /* remap? */
        if (l3pte_valid(opte)) {
@@ -1615,14 +1689,32 @@
                } else {
                        need_remove_pv = true;
                }
-               if (need_remove_pv) {
-                       opg = PHYS_TO_VM_PAGE(l3pte_pa(opte));
-                       if (opg != NULL) {
-                               opv = _pmap_remove_pv(opg, pm, va, opte);
+
+               if (need_remove_pv &&
+                   ((opg = PHYS_TO_VM_PAGE(l3pte_pa(opte))) != NULL)) {
+                       /* need to lock both pg and opg against deadlock */
+                       if (pg < opg) {
+                               pgs[0] = pg;
+                               pgs[1] = opg;
+                       } else {
+                               pgs[0] = opg;
+                               pgs[1] = pg;
                        }
+                       pmap_pv_lock(VM_PAGE_TO_MD(pgs[0]));
+                       pmap_pv_lock(VM_PAGE_TO_MD(pgs[1]));
+                       opv = _pmap_remove_pv(opg, pm, va, opte);
+               } else {
+                       if (pg != NULL)
+                               pmap_pv_lock(VM_PAGE_TO_MD(pg));
                }
+       } else {
+               if (pg != NULL)
+                       pmap_pv_lock(VM_PAGE_TO_MD(pg));
        }
 
+       if (!l3pte_valid(opte))
+               _pmap_pdp_addref(pm, pdppa, pdppg);     /* L3 occupancy++ */
+
        /*
         * read permission is treated as an access permission internally.
         * require to add PROT_READ even if only PROT_WRITE or PROT_EXEC
@@ -1700,17 +1792,16 @@
                AARCH64_TLBI_BY_ASID_VA(pm->pm_asid, va, l3only);
        }
 
-       if (!l3pte_valid(opte))
-               _pmap_pdp_addref(pm, pdppa, pdppg);     /* L3 occupancy++ */
-
        if (pte & LX_BLKPAG_OS_WIRED) {
                PMSTAT_INC_WIRED_COUNT(pm);
        }
        PMSTAT_INC_RESIDENT_COUNT(pm);
 
  fail1:
-       if (pg != NULL)
-               pmap_pv_unlock(VM_PAGE_TO_MD(pg));
+       if (pgs[1] != NULL)
+               pmap_pv_unlock(VM_PAGE_TO_MD(pgs[1]));
+       if (pgs[0] != NULL)
+               pmap_pv_unlock(VM_PAGE_TO_MD(pgs[0]));
  fail0:
        pm_unlock(pm);
 
diff -r 6102c95630ed -r 1189fb30744a sys/arch/aarch64/include/asan.h
--- a/sys/arch/aarch64/include/asan.h   Mon Apr 08 20:18:14 2019 +0000
+++ b/sys/arch/aarch64/include/asan.h   Mon Apr 08 21:18:22 2019 +0000
@@ -1,4 +1,4 @@
-/*     $NetBSD: asan.h,v 1.5 2019/03/19 16:05:49 ryo Exp $     */
+/*     $NetBSD: asan.h,v 1.6 2019/04/08 21:18:22 ryo Exp $     */
 
 /*
  * Copyright (c) 2018 The NetBSD Foundation, Inc.
@@ -70,7 +70,7 @@
        if (__predict_false(__md_early))
                pa = (paddr_t)bootpage_alloc();
        else
-               pa = pmap_alloc_pdp(pmap_kernel(), NULL, false);
+               pa = pmap_alloc_pdp(pmap_kernel(), NULL, 0, false);
 
        return pa;
 }
diff -r 6102c95630ed -r 1189fb30744a sys/arch/aarch64/include/pmap.h
--- a/sys/arch/aarch64/include/pmap.h   Mon Apr 08 20:18:14 2019 +0000
+++ b/sys/arch/aarch64/include/pmap.h   Mon Apr 08 21:18:22 2019 +0000
@@ -1,4 +1,4 @@
-/* $NetBSD: pmap.h,v 1.23 2019/03/19 16:45:28 ryo Exp $ */



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