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authorMartin Schwidefsky <schwidefsky@de.ibm.com>2008-12-31 15:11:42 +0100
committerMartin Schwidefsky <schwidefsky@de.ibm.com>2008-12-31 15:11:49 +0100
commitc742b31c03f37c5c499178f09f57381aa6c70131 (patch)
treedb0e95b8299d997fcb1264126bc8efe10d0ddd51 /arch/s390/kernel/vdso64
parent9cfb9b3c3a7361c793c031e9c3583b177ac5debd (diff)
[PATCH] fast vdso implementation for CLOCK_THREAD_CPUTIME_ID
The extract cpu time instruction (ectg) instruction allows the user process to get the current thread cputime without calling into the kernel. The code that uses the instruction needs to switch to the access registers mode to get access to the per-cpu info page that contains the two base values that are needed to calculate the current cputime from the CPU timer with the ectg instruction. Signed-off-by: Martin Schwidefsky <schwidefsky@de.ibm.com>
Diffstat (limited to 'arch/s390/kernel/vdso64')
-rw-r--r--arch/s390/kernel/vdso64/clock_getres.S5
-rw-r--r--arch/s390/kernel/vdso64/clock_gettime.S39
2 files changed, 39 insertions, 5 deletions
diff --git a/arch/s390/kernel/vdso64/clock_getres.S b/arch/s390/kernel/vdso64/clock_getres.S
index 488e31a3c0e..9ce8caafdb4 100644
--- a/arch/s390/kernel/vdso64/clock_getres.S
+++ b/arch/s390/kernel/vdso64/clock_getres.S
@@ -22,7 +22,12 @@ __kernel_clock_getres:
cghi %r2,CLOCK_REALTIME
je 0f
cghi %r2,CLOCK_MONOTONIC
+ je 0f
+ cghi %r2,-2 /* CLOCK_THREAD_CPUTIME_ID for this thread */
jne 2f
+ larl %r5,_vdso_data
+ icm %r0,15,__LC_ECTG_OK(%r5)
+ jz 2f
0: ltgr %r3,%r3
jz 1f /* res == NULL */
larl %r1,3f
diff --git a/arch/s390/kernel/vdso64/clock_gettime.S b/arch/s390/kernel/vdso64/clock_gettime.S
index 738a410b7eb..79dbfee831e 100644
--- a/arch/s390/kernel/vdso64/clock_gettime.S
+++ b/arch/s390/kernel/vdso64/clock_gettime.S
@@ -22,8 +22,10 @@ __kernel_clock_gettime:
larl %r5,_vdso_data
cghi %r2,CLOCK_REALTIME
je 4f
+ cghi %r2,-2 /* CLOCK_THREAD_CPUTIME_ID for this thread */
+ je 9f
cghi %r2,CLOCK_MONOTONIC
- jne 9f
+ jne 12f
/* CLOCK_MONOTONIC */
ltgr %r3,%r3
@@ -42,7 +44,7 @@ __kernel_clock_gettime:
alg %r0,__VDSO_WTOM_SEC(%r5)
clg %r4,__VDSO_UPD_COUNT(%r5) /* check update counter */
jne 0b
- larl %r5,10f
+ larl %r5,13f
1: clg %r1,0(%r5)
jl 2f
slg %r1,0(%r5)
@@ -68,7 +70,7 @@ __kernel_clock_gettime:
lg %r0,__VDSO_XTIME_SEC(%r5)
clg %r4,__VDSO_UPD_COUNT(%r5) /* check update counter */
jne 5b
- larl %r5,10f
+ larl %r5,13f
6: clg %r1,0(%r5)
jl 7f
slg %r1,0(%r5)
@@ -79,11 +81,38 @@ __kernel_clock_gettime:
8: lghi %r2,0
br %r14
+ /* CLOCK_THREAD_CPUTIME_ID for this thread */
+9: icm %r0,15,__VDSO_ECTG_OK(%r5)
+ jz 12f
+ ear %r2,%a4
+ llilh %r4,0x0100
+ sar %a4,%r4
+ lghi %r4,0
+ sacf 512 /* Magic ectg instruction */
+ .insn ssf,0xc80100000000,__VDSO_ECTG_BASE(4),__VDSO_ECTG_USER(4),4
+ sacf 0
+ sar %a4,%r2
+ algr %r1,%r0 /* r1 = cputime as TOD value */
+ mghi %r1,1000 /* convert to nanoseconds */
+ srlg %r1,%r1,12 /* r1 = cputime in nanosec */
+ lgr %r4,%r1
+ larl %r5,13f
+ srlg %r1,%r1,9 /* divide by 1000000000 */
+ mlg %r0,8(%r5)
+ srlg %r0,%r0,11 /* r0 = tv_sec */
+ stg %r0,0(%r3)
+ msg %r0,0(%r5) /* calculate tv_nsec */
+ slgr %r4,%r0 /* r4 = tv_nsec */
+ stg %r4,8(%r3)
+ lghi %r2,0
+ br %r14
+
/* Fallback to system call */
-9: lghi %r1,__NR_clock_gettime
+12: lghi %r1,__NR_clock_gettime
svc 0
br %r14
-10: .quad 1000000000
+13: .quad 1000000000
+14: .quad 19342813113834067
.cfi_endproc
.size __kernel_clock_gettime,.-__kernel_clock_gettime