Date: Fri, 8 Oct 1999 19:57:26 -0500 From: Alan Cox <alc@cs.rice.edu> To: Alfred Perlstein <bright@wintelcom.net> Cc: smp@freebsd.org Subject: Re: optimizing the idle-loop and more mp stuff Message-ID: <19991008195726.C36160@nonpc.cs.rice.edu> In-Reply-To: <Pine.BSF.4.05.9910081715240.8080-100000@fw.wintelcom.net>; from Alfred Perlstein on Fri, Oct 08, 1999 at 05:53:07PM -0700 References: <Pine.BSF.4.05.9910081715240.8080-100000@fw.wintelcom.net>
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--3MwIy2ne0vdjdPXF
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On Fri, Oct 08, 1999 at 05:53:07PM -0700, Alfred Perlstein wrote:
>
> I've been looking at the mplock stuff for a while now and I was
> wondering if someone could clarify some observations and assumptions
> I have.
>
> 1) the idle loop that zero's pages has the mplock up so that it
> can't even run on an idle CPU.
>
> It seems to me that this could be fixed by ripping some code from
> pmap_zero_page() specifically to map the page in and _then_ releasing
> the mplock, zero'ing the page and aquiring the mplock again.
>
> perhaps even grabbing several pages, mapping them in and the zero'ing
> them all in one sweep to lower the overhead of mplock manipulation.
>
Try updating/using the attached patch.
Alan
--3MwIy2ne0vdjdPXF
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Content-Disposition: attachment; filename="idle-lock.patch"
Index: i386/i386/vm_machdep.c
===================================================================
RCS file: /home/ncvs/src/sys/i386/i386/vm_machdep.c,v
retrieving revision 1.125
diff -c -r1.125 vm_machdep.c
*** vm_machdep.c 1999/07/31 18:30:49 1.125
--- vm_machdep.c 1999/08/19 17:05:56
***************
*** 546,570 ****
return(0);
#ifdef SMP
! if (try_mplock()) {
#endif
- s = splvm();
- __asm __volatile("sti" : : : "memory");
zero_state = 0;
m = vm_page_list_find(PQ_FREE, free_rover, FALSE);
if (m != NULL && (m->flags & PG_ZERO) == 0) {
vm_page_queues[m->queue].lcnt--;
TAILQ_REMOVE(vm_page_queues[m->queue].pl, m, pageq);
m->queue = PQ_NONE;
! splx(s);
! #if 0
! rel_mplock();
! #endif
pmap_zero_page(VM_PAGE_TO_PHYS(m));
! #if 0
! get_mplock();
! #endif
! (void)splvm();
vm_page_flag_set(m, PG_ZERO);
m->queue = PQ_FREE + m->pc;
vm_page_queues[m->queue].lcnt++;
--- 546,570 ----
return(0);
#ifdef SMP
! if (simple_lock_try(&vm_page_queue_free_mutex)) {
#endif
zero_state = 0;
m = vm_page_list_find(PQ_FREE, free_rover, FALSE);
if (m != NULL && (m->flags & PG_ZERO) == 0) {
vm_page_queues[m->queue].lcnt--;
TAILQ_REMOVE(vm_page_queues[m->queue].pl, m, pageq);
m->queue = PQ_NONE;
!
! simple_unlock(&vm_page_queue_free_mutex);
!
! __asm __volatile("sti" : : : "memory");
!
pmap_zero_page(VM_PAGE_TO_PHYS(m));
!
! __asm __volatile("cli" : : : "memory");
!
! simple_lock(&vm_page_queue_free_mutex);
!
vm_page_flag_set(m, PG_ZERO);
m->queue = PQ_FREE + m->pc;
vm_page_queues[m->queue].lcnt++;
***************
*** 576,585 ****
zero_state = 1;
}
free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK;
- splx(s);
- __asm __volatile("cli" : : : "memory");
#ifdef SMP
! rel_mplock();
#endif
return (1);
#ifdef SMP
--- 576,583 ----
zero_state = 1;
}
free_rover = (free_rover + PQ_PRIME2) & PQ_L2_MASK;
#ifdef SMP
! simple_unlock(&vm_page_queue_free_mutex);
#endif
return (1);
#ifdef SMP
Index: i386/include/smptests.h
===================================================================
RCS file: /home/ncvs/src/sys/i386/include/smptests.h,v
retrieving revision 1.32
diff -c -r1.32 smptests.h
*** smptests.h 1998/04/06 11:38:18 1.32
--- smptests.h 1999/08/19 08:14:57
***************
*** 129,135 ****
* panic()s, as simple locks are binary, and this would cause a deadlock.
*
*/
! #define SL_DEBUG
/*
--- 129,135 ----
* panic()s, as simple locks are binary, and this would cause a deadlock.
*
*/
! #define sL_DEBUG
/*
Index: vm/vm_page.c
===================================================================
RCS file: /home/ncvs/src/sys/vm/vm_page.c,v
retrieving revision 1.140
diff -c -r1.140 vm_page.c
*** vm_page.c 1999/08/17 18:09:01 1.140
--- vm_page.c 1999/08/19 07:26:49
***************
*** 88,93 ****
--- 88,94 ----
static void vm_page_queue_init __P((void));
static vm_page_t vm_page_select_cache __P((vm_object_t, vm_pindex_t));
+ static void _vm_page_free_toq(vm_page_t m);
/*
* Associated with page of user-allocatable memory is a
***************
*** 106,111 ****
--- 107,114 ----
struct vpgqueues vm_page_queues[PQ_COUNT] = {{0}};
+ struct simplelock vm_page_queue_free_mutex;
+
static void
vm_page_queue_init(void) {
int i;
***************
*** 130,135 ****
--- 133,139 ----
panic("vm_page_queue_init: queue %d is null", i);
}
}
+ simple_lock_init(&vm_page_queue_free_mutex);
}
vm_page_t vm_page_array = 0;
***************
*** 764,772 ****
if ((curproc == pageproc) && (page_req != VM_ALLOC_INTERRUPT)) {
page_req = VM_ALLOC_SYSTEM;
};
-
- s = splvm();
loop:
if (cnt.v_free_count > cnt.v_free_reserved) {
/*
--- 768,775 ----
if ((curproc == pageproc) && (page_req != VM_ALLOC_INTERRUPT)) {
page_req = VM_ALLOC_SYSTEM;
};
+ s = vm_page_queue_free_lock();
loop:
if (cnt.v_free_count > cnt.v_free_reserved) {
/*
***************
*** 795,801 ****
*/
m = vm_page_select_cache(object, pindex);
if (m == NULL) {
! splx(s);
#if defined(DIAGNOSTIC)
if (cnt.v_cache_count > 0)
printf("vm_page_alloc(NORMAL): missing pages on cache queue: %d\n", cnt.v_cache_count);
--- 798,804 ----
*/
m = vm_page_select_cache(object, pindex);
if (m == NULL) {
! vm_page_queue_free_unlock(s);
#if defined(DIAGNOSTIC)
if (cnt.v_cache_count > 0)
printf("vm_page_alloc(NORMAL): missing pages on cache queue: %d\n", cnt.v_cache_count);
***************
*** 807,819 ****
KASSERT(m->dirty == 0, ("Found dirty cache page %p", m));
vm_page_busy(m);
vm_page_protect(m, VM_PROT_NONE);
! vm_page_free(m);
goto loop;
} else {
/*
* Not allocateable from cache from interrupt, give up.
*/
! splx(s);
vm_pageout_deficit++;
pagedaemon_wakeup();
return (NULL);
--- 810,823 ----
KASSERT(m->dirty == 0, ("Found dirty cache page %p", m));
vm_page_busy(m);
vm_page_protect(m, VM_PROT_NONE);
! vm_page_flag_clear(m, PG_ZERO);
! _vm_page_free_toq(m);
goto loop;
} else {
/*
* Not allocateable from cache from interrupt, give up.
*/
! vm_page_queue_free_unlock(s);
vm_pageout_deficit++;
pagedaemon_wakeup();
return (NULL);
***************
*** 876,882 ****
(cnt.v_free_count < cnt.v_pageout_free_min))
pagedaemon_wakeup();
! splx(s);
return (m);
}
--- 880,886 ----
(cnt.v_free_count < cnt.v_pageout_free_min))
pagedaemon_wakeup();
! vm_page_queue_free_unlock(s);
return (m);
}
***************
*** 1066,1081 ****
* Object and page must be locked prior to entry.
* This routine may not block.
*/
-
void
vm_page_free_toq(vm_page_t m)
{
int s;
struct vpgqueues *pq;
vm_object_t object = m->object;
- s = splvm();
-
cnt.v_tfree++;
#if !defined(MAX_PERF)
--- 1070,1091 ----
* Object and page must be locked prior to entry.
* This routine may not block.
*/
void
vm_page_free_toq(vm_page_t m)
{
int s;
+
+ s = vm_page_queue_free_lock();
+ _vm_page_free_toq(m);
+ vm_page_queue_free_unlock(s);
+ }
+
+ static void
+ _vm_page_free_toq(vm_page_t m)
+ {
struct vpgqueues *pq;
vm_object_t object = m->object;
cnt.v_tfree++;
#if !defined(MAX_PERF)
***************
*** 1108,1114 ****
*/
if ((m->flags & PG_FICTITIOUS) != 0) {
- splx(s);
return;
}
--- 1118,1123 ----
***************
*** 1168,1175 ****
}
vm_page_free_wakeup();
-
- splx(s);
}
/*
--- 1177,1182 ----
Index: vm/vm_page.h
===================================================================
RCS file: /home/ncvs/src/sys/vm/vm_page.h,v
retrieving revision 1.70
diff -c -r1.70 vm_page.h
*** vm_page.h 1999/08/17 22:48:10 1.70
--- vm_page.h 1999/08/19 16:59:44
***************
*** 280,285 ****
--- 280,310 ----
#endif
+ #ifdef SMP
+ extern struct simplelock vm_page_queue_free_mutex;
+ #endif
+
+ static __inline int
+ vm_page_queue_free_lock(void)
+ {
+ int s;
+
+ s = splvm();
+ #ifdef SMP
+ simple_lock(&vm_page_queue_free_mutex);
+ #endif
+ return s;
+ }
+
+ static __inline void
+ vm_page_queue_free_unlock(int s)
+ {
+ #ifdef SMP
+ simple_unlock(&vm_page_queue_free_mutex);
+ #endif
+ splx(s);
+ }
+
extern int vm_page_zero_count;
extern vm_page_t vm_page_array; /* First resident page in table */
--3MwIy2ne0vdjdPXF--
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