cvs commit: src/sys/amd64/amd64 pmap.c src/sys/arm/arm pmap.c src/sys/i386/i386 pmap.c src/sys/ia64/ia64 pmap.c src/sys/powerpc/powerpc mmu_oea.c src/sys/sparc64/sparc64 pmap.c src/sys/sun4v/sun4v pmap.c src/sys/vm vm_fault.c vm_kern.c

[Kip Macy]

Thanks Alan, this is a definite improvement.

For the benefit of other readers: below I have the ten locks with longest
max_wait (total time in microseconds spent waiting for the lock) during the
compile phase of a "make -j32 buildkernel" on a T2000 (8 cores w/ 4 threads
per core). The reduction in turnstile contention is a direct result of
reducing contention on the page queue mutex.

before:
  max        total   wait_total       count   avg wait_avg     cnt_hold
cnt_lock name
     5      7266196    206805560     7522452     0    27
48266619            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/kern/subr_turnstile.c:487
(turnstile chain)
   457       528521    180592127      550284     0   328
1469872            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/vm/vm_fault.c:844 (vm page queue
mutex)
15057461   1679582934    117520488       87978 19090  1335
0            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/ufs/ffs/ffs_vnops.c:366 (ufs)
   214      1076256    112489341      559032     1   201
1520471            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/vm/vm_fault.c:902 (vm page queue
mutex)
   424      8250360    105249196      559031    14   188
1767340            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/sun4v/sun4v/pmap.c:956 (vm page
queue mutex)
72563452121 218316084315     94216669      452713 482239   208
0            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/kern/vfs_default.c:263 (nfs)
    23      1349030     14049785      280685     4    50
923679            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/kern/kern_idle.c:121 (sched lock)
    73       214117     11078161       63944     3   173
2505            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/nfsclient/nfs_socket.c:1235
(Giant)
    42        92768     10431233       40012     2   260
122966            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/vm/vm_fault.c:342 (vm page queue
mutex)
  6429      2155581      6645086       18297   117   363
105550            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/vm/vm_object.c:651 (vm page queue
mutex)


after:
15311133   1125368615    119287635       94194 11947  1266
0            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/ufs/ffs/ffs_vnops.c:366
(lockmgr:ufs)
   546      4708767     93794515      326286    14   287       533239
713529 /usr/flatstor/shared/freebsd/kmacy/src/sys/sun4v/sun4v/pmap.c:955
(sleep mutex:vm page queue mutex)
36217304    520567907     53857789      243928  2134   220
0            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/kern/vfs_default.c:263
(lockmgr:nfs)
   210       590989     38380260      326286     1   117       335955
160913 /usr/flatstor/shared/freebsd/kmacy/src/sys/vm/vm_fault.c:899 (sleep
mutex:vm page queue mutex)
    16      1702987     25490112     2068283     0    12
7329498            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/kern/subr_turnstile.c:487 (spin
mutex:turnstile chain)
    22       962236      7498290      194839     4    38
665502            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/kern/kern_idle.c:121 (spin
mutex:sched lock)
     9        28157      4130053        7242     3   570
9959         3040
/usr/flatstor/shared/freebsd/kmacy/src/sys/sun4v/sun4v/pmap.c:1162 (sleep
mutex:vm page queue mutex)
    39        44908      2629172       21967     2   119        21879
11174 /usr/flatstor/shared/freebsd/kmacy/src/sys/vm/vm_fault.c:342 (sleep
mutex:vm page queue mutex)
     4        20673      2265592       21708     0   104
88367            0
/usr/flatstor/shared/freebsd/kmacy/src/sys/kern/subr_trap.c:191 (spin
mutex:sched lock)
    31        11117      2231209        7243     1   308
7419         3023
/usr/flatstor/shared/freebsd/kmacy/src/sys/kern/sys_pipe.c:827 (sleep
mutex:vm page queue mutex)


On 11/12/06, Alan Cox <alc at freebsd.org> wrote:
>
> alc         2006-11-12 21:48:34 UTC
>
>   FreeBSD src repository
>
>   Modified files:
>     sys/amd64/amd64      pmap.c
>     sys/arm/arm          pmap.c
>     sys/i386/i386        pmap.c
>     sys/ia64/ia64         pmap.c
>     sys/powerpc/powerpc  mmu_oea.c
>     sys/sparc64/sparc64  pmap.c
>     sys/sun4v/sun4v      pmap.c
>     sys/vm               vm_fault.c vm_kern.c
>   Log:
>   Make pmap_enter() responsible for setting PG_WRITEABLE instead
>   of its caller.  (As a beneficial side-effect, a high-contention
>   acquisition of the page queues lock in vm_fault() is eliminated.)
>
>   Revision  Changes    Path
>   1.573     +3 -1      src/sys/amd64/amd64/pmap.c
>   1.73      +4 -1      src/sys/arm/arm/pmap.c
>   1.577     +3 -1      src/sys/i386/i386/pmap.c
>   1.180     +2 -0      src/sys/ia64/ia64/pmap.c
>   1.112     +3 -2      src/sys/powerpc/powerpc/mmu_oea.c
>   1.160      +4 -1      src/sys/sparc64/sparc64/pmap.c
>   1.6       +3 -1      src/sys/sun4v/sun4v/pmap.c
>   1.223     +2 -7      src/sys/vm/vm_fault.c
>   1.124     +1 -1      src/sys/vm/vm_kern.c
>