Hi,
I was looking at the 45% regression reported by Yanmin, when while running the
test, I ran into
1:mon> t
[c0000000e7677da0] c000000000067de0 .sys_sched_yield+0x6c/0xbc
[c0000000e7677e30] c000000000008748 syscall_exit+0x0/0x40
--- Exception: c01 (System Call) at 00000400001d09e4
SP (4000664cb10) is in userspace
1:mon> r
R00 = 0000000000000001 R16 = 0000000000000000
R01 = c0000000e7677d20 R17 = 0000000000000000
R02 = c000000000949490 R18 = 00000000100c5290
R03 = 0000000000000008 R19 = 0000000000000000
R04 = 0000000010036370 R20 = 0000000010040bc0
R05 = 0000000000000000 R21 = 0000000000000000
R06 = 0000000000000001 R22 = 0000000000000002
R07 = 000000000000002d R23 = 0000000000000008
R08 = 0000000000000000 R24 = 00000000100387c0
R09 = 0000000000000000 R25 = 0000000010038c20
R10 = c0000000e5c12520 R26 = 00000000100363e8
R11 = c0000000e5c12558 R27 = 0000000010038c50
R12 = 800000000000f032 R28 = 0000000000360000
R13 = c00000000083c300 R29 = c000000000b43b80
R14 = 0000040000ee6e0d R30 = c0000000008ba608
R15 = 0000000000000000 R31 = c000000000b42680
pc = c000000000068e50 .yield_task_fair+0x94/0xc4
lr = c000000000067de0 .sys_sched_yield+0x6c/0xbc
msr = 8000000000009032 cr = 24204482
ctr = c000000000068dbc xer = 0000000020000010 trap = 300
dar = 0000000000000050 dsisr = 40000000
1:mon> e
cpu 0x1: Vector: 300 (Data Access) at [c0000000e7677aa0]
pc: c000000000068e50: .yield_task_fair+0x94/0xc4
lr: c000000000067de0: .sys_sched_yield+0x6c/0xbc
sp: c0000000e7677d20
msr: 8000000000009032
dar: 50
dsisr: 40000000
current = 0xc0000000e5c12520
paca = 0xc00000000083c300
pid = 569, comm = java
1:mon> di %pc
c000000000068e50 e9280050 ld r9,80(r8)
c000000000068e54 e80b0050 ld r0,80(r11)
c000000000068e58 7fa90040 cmpld cr7,r9,r0
c000000000068e5c 419c000c blt cr7,c000000000068e68 #
.yield_task_fair+0xac/0xc4
c000000000068e60 38090001 addi r0,r9,1
c000000000068e64 f80b0050 std r0,80(r11)
c000000000068e68 38210080 addi r1,r1,128
c000000000068e6c e8010010 ld r0,16(r1)
c000000000068e70 ebc1fff0 ld r30,-16(r1)
c000000000068e74 ebe1fff8 ld r31,-8(r1)
c000000000068e78 7c0803a6 mtlr r0
c000000000068e7c 4e800020 blr
c000000000068e80 7c0802a6 mflr r0
c000000000068e84 fba1ffe8 std r29,-24(r1)
c000000000068e88 fbe1fff8 std r31,-8(r1)
c000000000068e8c f8010010 std r0,16(r1)
Matching assembly and symbols, the code turned out to be around
/*
* Find the rightmost entry in the rbtree:
*/
rightmost = __pick_last_entity(&rq->cfs);
/*
* Already in the rightmost position?
*/
if (unlikely(rightmost->vruntime < se->vruntime))
return;
It looked like rightmost was set to NULL. I am going to try and find some time
in tomorrow and see if I can debug it further.
--
Warm Regards,
Balbir Singh
Linux Technology Center
IBM, ISTL
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