On 22/12/20(Tue) 23:43, Mark Kettenis wrote:
> > Date: Mon, 21 Dec 2020 16:46:32 -0300
> > From: Martin Pieuchot <m...@openbsd.org>
> >
> > During a page fault multiples counters are updated. They fall into two
> > categories "fault counters" and "global statistics" both of which are
> > currently represented by int-sized fields inside a global: `uvmexp'.
> >
> > Diff below makes use of the per-CPU counters_inc(9) API to make sure no
> > update is lost with an unlocked fault handler. I only converted the
> > fields touched by uvm_fault() to have a working solution and start a
> > discussion.
> >
> > - Should we keep a single enum for all fields inside `uvmexp' or do we
> > want to separate "statistics counters" which are mostly used sys/arch
> > from "fault counters" which are only used in uvm/uvm_fault.c?
> >
> > - The counter_add(9) API deals with uint64_t and currently uvmexp uses
> > int. Should we truncate or change the size of uvmexp fields or do
> > something else?
> >
> > Comments?
>
> I think this breaks "show uvmexp" in ddb.
Updated diff below fixes that. Any comment on the issues raised above?
> You fear that using atomic operations for these counters would lead to
> too much bus contention on systems with a large number of CPUs?
I don't know. I don't see the point of using atomic operations for
"real" counters that are not used to make any decision. Atomic
operations have a high cost, bus contention might be one of them.
Index: kern/init_main.c
===================================================================
RCS file: /cvs/src/sys/kern/init_main.c,v
retrieving revision 1.302
diff -u -p -r1.302 init_main.c
--- kern/init_main.c 7 Dec 2020 16:55:28 -0000 1.302
+++ kern/init_main.c 21 Dec 2020 19:37:13 -0000
@@ -432,6 +432,7 @@ main(void *framep)
#endif
mbcpuinit(); /* enable per cpu mbuf data */
+ uvm_init_percpu();
/* init exec and emul */
init_exec();
Index: uvm/uvm_extern.h
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_extern.h,v
retrieving revision 1.155
diff -u -p -r1.155 uvm_extern.h
--- uvm/uvm_extern.h 1 Dec 2020 13:56:22 -0000 1.155
+++ uvm/uvm_extern.h 21 Dec 2020 19:37:13 -0000
@@ -289,6 +289,7 @@ void uvm_vsunlock_device(struct proc
*
void *);
void uvm_pause(void);
void uvm_init(void);
+void uvm_init_percpu(void);
int uvm_io(vm_map_t, struct uio *, int);
#define UVM_IO_FIXPROT 0x01
Index: uvm/uvm_fault.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_fault.c,v
retrieving revision 1.109
diff -u -p -r1.109 uvm_fault.c
--- uvm/uvm_fault.c 8 Dec 2020 12:26:31 -0000 1.109
+++ uvm/uvm_fault.c 21 Dec 2020 19:37:13 -0000
@@ -35,6 +35,7 @@
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
+#include <sys/percpu.h>
#include <sys/proc.h>
#include <sys/malloc.h>
#include <sys/mman.h>
@@ -271,7 +272,7 @@ uvmfault_anonget(struct uvm_faultinfo *u
int result;
result = 0; /* XXX shut up gcc */
- uvmexp.fltanget++;
+ counters_inc(uvmexp_counters, flt_anget);
/* bump rusage counters */
if (anon->an_page)
curproc->p_ru.ru_minflt++;
@@ -295,7 +296,7 @@ uvmfault_anonget(struct uvm_faultinfo *u
if ((pg->pg_flags & (PG_BUSY|PG_RELEASED)) == 0)
return (VM_PAGER_OK);
atomic_setbits_int(&pg->pg_flags, PG_WANTED);
- uvmexp.fltpgwait++;
+ counters_inc(uvmexp_counters, flt_pgwait);
/*
* the last unlock must be an atomic unlock+wait on
@@ -310,7 +311,7 @@ uvmfault_anonget(struct uvm_faultinfo *u
if (pg == NULL) { /* out of RAM. */
uvmfault_unlockall(ufi, amap, NULL);
- uvmexp.fltnoram++;
+ counters_inc(uvmexp_counters, flt_noram);
uvm_wait("flt_noram1");
/* ready to relock and try again */
} else {
@@ -325,7 +326,7 @@ uvmfault_anonget(struct uvm_faultinfo *u
* it is ok to read an_swslot here because
* we hold PG_BUSY on the page.
*/
- uvmexp.pageins++;
+ counters_inc(uvmexp_counters, pageins);
result = uvm_swap_get(pg, anon->an_swslot,
PGO_SYNCIO);
@@ -369,7 +370,7 @@ uvmfault_anonget(struct uvm_faultinfo *u
uvm_anfree(anon); /* frees page for us */
if (locked)
uvmfault_unlockall(ufi, amap, NULL);
- uvmexp.fltpgrele++;
+ counters_inc(uvmexp_counters, flt_pgrele);
return (VM_PAGER_REFAULT); /* refault! */
}
@@ -426,7 +427,7 @@ uvmfault_anonget(struct uvm_faultinfo *u
}
/* try it again! */
- uvmexp.fltanretry++;
+ counters_inc(uvmexp_counters, flt_anretry);
continue;
} /* while (1) */
@@ -547,7 +548,7 @@ uvm_fault_check(struct uvm_faultinfo *uf
/* need to clear */
uvmfault_unlockmaps(ufi, FALSE);
uvmfault_amapcopy(ufi);
- uvmexp.fltamcopy++;
+ counters_inc(uvmexp_counters, flt_amcopy);
return (ERESTART);
} else {
/*
@@ -699,7 +700,7 @@ uvm_fault_upper(struct uvm_faultinfo *uf
*/
if ((access_type & PROT_WRITE) != 0 && anon->an_ref > 1) {
- uvmexp.flt_acow++;
+ counters_inc(uvmexp_counters, flt_acow);
oanon = anon; /* oanon = old */
anon = uvm_analloc();
if (anon) {
@@ -710,10 +711,10 @@ uvm_fault_upper(struct uvm_faultinfo *uf
if (anon == NULL || pg == NULL) {
uvmfault_unlockall(ufi, amap, NULL);
if (anon == NULL)
- uvmexp.fltnoanon++;
+ counters_inc(uvmexp_counters, flt_noanon);
else {
uvm_anfree(anon);
- uvmexp.fltnoram++;
+ counters_inc(uvmexp_counters, flt_noram);
}
if (uvm_swapisfull())
@@ -745,7 +746,7 @@ uvm_fault_upper(struct uvm_faultinfo *uf
* thus, no one can get at it until we are done with it.
*/
} else {
- uvmexp.flt_anon++;
+ counters_inc(uvmexp_counters, flt_anon);
oanon = anon;
pg = anon->an_page;
if (anon->an_ref > 1) /* disallow writes to ref > 1 anons */
@@ -861,7 +862,7 @@ uvm_fault_upper_lookup(struct uvm_faulti
uvm_lock_pageq();
uvm_pageactivate(anon->an_page); /* reactivate */
uvm_unlock_pageq();
- uvmexp.fltnamap++;
+ counters_inc(uvmexp_counters, flt_namap);
/*
* Since this isn't the page that's actually faulting,
@@ -909,7 +910,7 @@ uvm_fault(vm_map_t orig_map, vaddr_t vad
struct vm_page *pages[UVM_MAXRANGE];
int error = ERESTART;
- uvmexp.faults++; /* XXX: locking? */
+ counters_inc(uvmexp_counters, faults);
TRACEPOINT(uvm, fault, vaddr, fault_type, access_type, NULL);
/* init the IN parameters in the ufi */
@@ -994,7 +995,7 @@ uvm_fault_lower(struct uvm_faultinfo *uf
* ("get" has the option of doing a pmap_enter for us)
*/
if (uobj != NULL) {
- uvmexp.fltlget++;
+ counters_inc(uvmexp_counters, flt_lget);
gotpages = flt->npages;
(void) uobj->pgops->pgo_get(uobj, ufi->entry->offset +
(flt->startva - ufi->entry->start),
@@ -1038,7 +1039,7 @@ uvm_fault_lower(struct uvm_faultinfo *uf
uvm_lock_pageq();
uvm_pageactivate(pages[lcv]); /* reactivate */
uvm_unlock_pageq();
- uvmexp.fltnomap++;
+ counters_inc(uvmexp_counters, flt_nomap);
/*
* Since this page isn't the page that's
@@ -1109,7 +1110,7 @@ uvm_fault_lower(struct uvm_faultinfo *uf
uvmfault_unlockall(ufi, amap, NULL);
- uvmexp.fltget++;
+ counters_inc(uvmexp_counters, flt_get);
gotpages = 1;
uoff = (ufi->orig_rvaddr - ufi->entry->start) +
ufi->entry->offset;
result = uobj->pgops->pgo_get(uobj, uoff, &uobjpage, &gotpages,
@@ -1183,7 +1184,7 @@ uvm_fault_lower(struct uvm_faultinfo *uf
*
* set "pg" to the page we want to map in (uobjpage, usually)
*/
- uvmexp.flt_obj++;
+ counters_inc(uvmexp_counters, flt_obj);
if (UVM_ET_ISCOPYONWRITE(ufi->entry))
flt->enter_prot &= ~PROT_WRITE;
pg = uobjpage; /* map in the actual object */
@@ -1235,10 +1236,10 @@ uvm_fault_lower(struct uvm_faultinfo *uf
/* unlock and fail ... */
uvmfault_unlockall(ufi, amap, uobj);
if (anon == NULL)
- uvmexp.fltnoanon++;
+ counters_inc(uvmexp_counters, flt_noanon);
else {
uvm_anfree(anon);
- uvmexp.fltnoram++;
+ counters_inc(uvmexp_counters, flt_noram);
}
if (uvm_swapisfull())
@@ -1254,7 +1255,7 @@ uvm_fault_lower(struct uvm_faultinfo *uf
/* fill in the data */
if (uobjpage != PGO_DONTCARE) {
- uvmexp.flt_prcopy++;
+ counters_inc(uvmexp_counters, flt_prcopy);
/* copy page [pg now dirty] */
uvm_pagecopy(uobjpage, pg);
@@ -1277,7 +1278,7 @@ uvm_fault_lower(struct uvm_faultinfo *uf
uvm_unlock_pageq();
uobj = NULL;
} else {
- uvmexp.flt_przero++;
+ counters_inc(uvmexp_counters, flt_przero);
/*
* Page is zero'd and marked dirty by uvm_pagealloc()
* above.
@@ -1288,7 +1289,7 @@ uvm_fault_lower(struct uvm_faultinfo *uf
ufi->orig_rvaddr - ufi->entry->start, anon, 0)) {
uvmfault_unlockall(ufi, amap, NULL);
uvm_anfree(anon);
- uvmexp.fltnoamap++;
+ counters_inc(uvmexp_counters, flt_noamap);
if (uvm_swapisfull())
return (ENOMEM);
@@ -1580,7 +1581,7 @@ uvmfault_relock(struct uvm_faultinfo *uf
return TRUE;
}
- uvmexp.fltrelck++;
+ counters_inc(uvmexp_counters, flt_relck);
/*
* relock map. fail if version mismatch (in which case nothing
@@ -1592,6 +1593,6 @@ uvmfault_relock(struct uvm_faultinfo *uf
return(FALSE);
}
- uvmexp.fltrelckok++;
+ counters_inc(uvmexp_counters, flt_relckok);
return(TRUE); /* got it! */
}
Index: uvm/uvm_init.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_init.c,v
retrieving revision 1.40
diff -u -p -r1.40 uvm_init.c
--- uvm/uvm_init.c 11 May 2017 00:42:05 -0000 1.40
+++ uvm/uvm_init.c 21 Dec 2020 19:37:13 -0000
@@ -35,6 +35,7 @@
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/filedesc.h>
+#include <sys/percpu.h>
#include <sys/resourcevar.h>
#include <sys/mman.h>
#include <sys/malloc.h>
@@ -52,6 +53,9 @@
struct uvm uvm; /* decl */
struct uvmexp uvmexp; /* decl */
+COUNTERS_BOOT_MEMORY(uvmexp_countersboot, exp_ncounters);
+struct cpumem *uvmexp_counters =
COUNTERS_BOOT_INITIALIZER(uvmexp_countersboot);
+
#if defined(VM_MIN_KERNEL_ADDRESS)
vaddr_t vm_min_kernel_address = VM_MIN_KERNEL_ADDRESS;
#else
@@ -184,4 +188,10 @@ uvm_init(void)
uaddr_bestfit_create(vm_map_min(kmem_map),
vm_map_max(kmem_map)));
#endif /* !SMALL_KERNEL */
+}
+
+void
+uvm_init_percpu(void)
+{
+ uvmexp_counters = counters_alloc_ncpus(uvmexp_counters, exp_ncounters);
}
Index: uvm/uvm_meter.c
===================================================================
RCS file: /cvs/src/sys/uvm/uvm_meter.c,v
retrieving revision 1.41
diff -u -p -r1.41 uvm_meter.c
--- uvm/uvm_meter.c 24 Jun 2020 22:03:45 -0000 1.41
+++ uvm/uvm_meter.c 23 Dec 2020 13:26:40 -0000
@@ -39,6 +39,7 @@
#include <sys/param.h>
#include <sys/systm.h>
#include <sys/kernel.h>
+#include <sys/percpu.h>
#include <sys/proc.h>
#include <sys/sysctl.h>
#include <sys/vmmeter.h>
@@ -78,6 +79,7 @@ static fixpt_t cexp[3] = {
static void uvm_loadav(struct loadavg *);
void uvm_total(struct vmtotal *);
+void uvmexp_read(struct uvmexp *);
/*
* uvm_meter: calculate load average and wake up the swapper (if needed)
@@ -151,6 +153,7 @@ uvm_sysctl(int *name, u_int namelen, voi
{
struct process *pr = p->p_p;
struct vmtotal vmtotals;
+ struct uvmexp uexp;
int rv, t;
switch (name[0]) {
@@ -179,8 +182,9 @@ uvm_sysctl(int *name, u_int namelen, voi
sizeof(vmtotals)));
case VM_UVMEXP:
- return (sysctl_rdstruct(oldp, oldlenp, newp, &uvmexp,
- sizeof(uvmexp)));
+ uvmexp_read(&uexp);
+ return (sysctl_rdstruct(oldp, oldlenp, newp, &uexp,
+ sizeof(uexp)));
case VM_NKMEMPAGES:
return (sysctl_rdint(oldp, oldlenp, newp, nkmempages));
@@ -315,6 +319,41 @@ uvm_total(struct vmtotal *totalp)
totalp->t_armshr = 0; /* XXX */
}
+void
+uvmexp_read(struct uvmexp *uexp)
+{
+ uint64_t counters[exp_ncounters];
+
+ memcpy(uexp, &uvmexp, sizeof(*uexp));
+
+ counters_read(uvmexp_counters, counters, exp_ncounters);
+
+ /* stat counters */
+ uexp->faults = (int)counters[faults];
+ uexp->pageins = (int)counters[pageins];
+
+ /* fault subcounters */
+ uexp->fltnoram = (int)counters[flt_noram];
+ uexp->fltnoanon = (int)counters[flt_noanon];
+ uexp->fltnoamap = (int)counters[flt_noamap];
+ uexp->fltpgwait = (int)counters[flt_pgwait];
+ uexp->fltpgrele = (int)counters[flt_pgrele];
+ uexp->fltrelck = (int)counters[flt_relck];
+ uexp->fltrelckok = (int)counters[flt_relckok];
+ uexp->fltanget = (int)counters[flt_anget];
+ uexp->fltanretry = (int)counters[flt_anretry];
+ uexp->fltamcopy = (int)counters[flt_amcopy];
+ uexp->fltnamap = (int)counters[flt_namap];
+ uexp->fltnomap = (int)counters[flt_nomap];
+ uexp->fltlget = (int)counters[flt_lget];
+ uexp->fltget = (int)counters[flt_get];
+ uexp->flt_anon = (int)counters[flt_anon];
+ uexp->flt_acow = (int)counters[flt_acow];
+ uexp->flt_obj = (int)counters[flt_obj];
+ uexp->flt_prcopy = (int)counters[flt_prcopy];
+ uexp->flt_przero = (int)counters[flt_przero];
+}
+
#ifdef DDB
/*
@@ -323,51 +362,54 @@ uvm_total(struct vmtotal *totalp)
void
uvmexp_print(int (*pr)(const char *, ...))
{
+ struct uvmexp uexp;
+
+ uvmexp_read(&uexp);
(*pr)("Current UVM status:\n");
(*pr)(" pagesize=%d (0x%x), pagemask=0x%x, pageshift=%d\n",
- uvmexp.pagesize, uvmexp.pagesize, uvmexp.pagemask,
- uvmexp.pageshift);
+ uexp.pagesize, uexp.pagesize, uexp.pagemask,
+ uexp.pageshift);
(*pr)(" %d VM pages: %d active, %d inactive, %d wired, %d free (%d
zero)\n",
- uvmexp.npages, uvmexp.active, uvmexp.inactive, uvmexp.wired,
- uvmexp.free, uvmexp.zeropages);
+ uexp.npages, uexp.active, uexp.inactive, uexp.wired,
+ uexp.free, uexp.zeropages);
(*pr)(" min %d%% (%d) anon, %d%% (%d) vnode, %d%% (%d) vtext\n",
- uvmexp.anonminpct, uvmexp.anonmin, uvmexp.vnodeminpct,
- uvmexp.vnodemin, uvmexp.vtextminpct, uvmexp.vtextmin);
+ uexp.anonminpct, uexp.anonmin, uexp.vnodeminpct,
+ uexp.vnodemin, uexp.vtextminpct, uexp.vtextmin);
(*pr)(" freemin=%d, free-target=%d, inactive-target=%d, "
- "wired-max=%d\n", uvmexp.freemin, uvmexp.freetarg, uvmexp.inactarg,
- uvmexp.wiredmax);
+ "wired-max=%d\n", uexp.freemin, uexp.freetarg, uexp.inactarg,
+ uexp.wiredmax);
(*pr)(" faults=%d, traps=%d, intrs=%d, ctxswitch=%d fpuswitch=%d\n",
- uvmexp.faults, uvmexp.traps, uvmexp.intrs, uvmexp.swtch,
- uvmexp.fpswtch);
+ uexp.faults, uexp.traps, uexp.intrs, uexp.swtch,
+ uexp.fpswtch);
(*pr)(" softint=%d, syscalls=%d, kmapent=%d\n",
- uvmexp.softs, uvmexp.syscalls, uvmexp.kmapent);
+ uexp.softs, uexp.syscalls, uexp.kmapent);
(*pr)(" fault counts:\n");
(*pr)(" noram=%d, noanon=%d, noamap=%d, pgwait=%d, pgrele=%d\n",
- uvmexp.fltnoram, uvmexp.fltnoanon, uvmexp.fltnoamap,
- uvmexp.fltpgwait, uvmexp.fltpgrele);
+ uexp.fltnoram, uexp.fltnoanon, uexp.fltnoamap,
+ uexp.fltpgwait, uexp.fltpgrele);
(*pr)(" ok relocks(total)=%d(%d), anget(retries)=%d(%d), "
- "amapcopy=%d\n", uvmexp.fltrelckok, uvmexp.fltrelck,
- uvmexp.fltanget, uvmexp.fltanretry, uvmexp.fltamcopy);
+ "amapcopy=%d\n", uexp.fltrelckok, uexp.fltrelck,
+ uexp.fltanget, uexp.fltanretry, uexp.fltamcopy);
(*pr)(" neighbor anon/obj pg=%d/%d, gets(lock/unlock)=%d/%d\n",
- uvmexp.fltnamap, uvmexp.fltnomap, uvmexp.fltlget, uvmexp.fltget);
+ uexp.fltnamap, uexp.fltnomap, uexp.fltlget, uexp.fltget);
(*pr)(" cases: anon=%d, anoncow=%d, obj=%d, prcopy=%d, przero=%d\n",
- uvmexp.flt_anon, uvmexp.flt_acow, uvmexp.flt_obj, uvmexp.flt_prcopy,
- uvmexp.flt_przero);
+ uexp.flt_anon, uexp.flt_acow, uexp.flt_obj, uexp.flt_prcopy,
+ uexp.flt_przero);
(*pr)(" daemon and swap counts:\n");
(*pr)(" woke=%d, revs=%d, scans=%d, obscans=%d, anscans=%d\n",
- uvmexp.pdwoke, uvmexp.pdrevs, uvmexp.pdscans, uvmexp.pdobscan,
- uvmexp.pdanscan);
+ uexp.pdwoke, uexp.pdrevs, uexp.pdscans, uexp.pdobscan,
+ uexp.pdanscan);
(*pr)(" busy=%d, freed=%d, reactivate=%d, deactivate=%d\n",
- uvmexp.pdbusy, uvmexp.pdfreed, uvmexp.pdreact, uvmexp.pddeact);
- (*pr)(" pageouts=%d, pending=%d, nswget=%d\n", uvmexp.pdpageouts,
- uvmexp.pdpending, uvmexp.nswget);
+ uexp.pdbusy, uexp.pdfreed, uexp.pdreact, uexp.pddeact);
+ (*pr)(" pageouts=%d, pending=%d, nswget=%d\n", uexp.pdpageouts,
+ uexp.pdpending, uexp.nswget);
(*pr)(" nswapdev=%d\n",
- uvmexp.nswapdev);
+ uexp.nswapdev);
(*pr)(" swpages=%d, swpginuse=%d, swpgonly=%d paging=%d\n",
- uvmexp.swpages, uvmexp.swpginuse, uvmexp.swpgonly, uvmexp.paging);
+ uexp.swpages, uexp.swpginuse, uexp.swpgonly, uexp.paging);
(*pr)(" kernel pointers:\n");
(*pr)(" objs(kern)=%p\n", uvm.kernel_object);
Index: uvm/uvmexp.h
===================================================================
RCS file: /cvs/src/sys/uvm/uvmexp.h,v
retrieving revision 1.7
diff -u -p -r1.7 uvmexp.h
--- uvm/uvmexp.h 14 Dec 2020 13:29:18 -0000 1.7
+++ uvm/uvmexp.h 21 Dec 2020 19:37:13 -0000
@@ -156,4 +156,41 @@ struct _ps_strings {
void *val;
};
+#ifdef _KERNEL
+
+/*
+ * Per-cpu UVM counters.
+ */
+extern struct cpumem *uvmexp_counters;
+
+enum uvm_exp_counters {
+ /* stat counters */
+ faults, /* page fault count */
+ pageins, /* pagein operation count */
+
+ /* fault subcounters */
+ flt_noram, /* number of times fault was out of ram */
+ flt_noanon, /* number of times fault was out of anons */
+ flt_noamap, /* number of times fault was out of amap chunks */
+ flt_pgwait, /* number of times fault had to wait on a page */
+ flt_pgrele, /* number of times fault found a released page */
+ flt_relck, /* number of times fault relock called */
+ flt_relckok, /* number of times fault relock is a success */
+ flt_anget, /* number of times fault gets anon page */
+ flt_anretry, /* number of times fault retrys an anon get */
+ flt_amcopy, /* number of times fault clears "needs copy" */
+ flt_namap, /* number of times fault maps a neighbor anon page */
+ flt_nomap, /* number of times fault maps a neighbor obj page */
+ flt_lget, /* number of times fault does a locked pgo_get */
+ flt_get, /* number of times fault does an unlocked get */
+ flt_anon, /* number of times fault anon (case 1a) */
+ flt_acow, /* number of times fault anon cow (case 1b) */
+ flt_obj, /* number of times fault is on object page (2a) */
+ flt_prcopy, /* number of times fault promotes with copy (2b) */
+ flt_przero, /* number of times fault promotes with zerofill (2b) */
+
+ exp_ncounters
+};
+
+#endif /* _KERNEL */
#endif /*_UVM_UVMEXP_ */
