Re: 2.6.0-test5-mm3 as-iosched Oops running dbt2 workload
From: Nick Piggin
Date: Fri Sep 19 2003 - 20:30:48 EST
Sigh. Sorry, I'm an idiot...
If a request is merged with another, it sometimes has to be repositioned
on the rbtree - you just do a delete then an add. This is a quite
uncommon case though.
I changed the way adding works, so collisions must be handled by the
caller instead of being dumbly fixed by the add routine. Unfortunately
the uncommon callers weren't handling it properly. Try this please.
Dave Olien wrote:
Andrew,
Attached is console output containing a stack trace from an Oops, followed
by a Fatal exception, and LOTS of APIC errors. The machine was hung,
printing APIC error messages forever.
This looks like another as-iosched problem. So, I'm copying Nick Piggin
on this email. But the Fatal exception and APIC errors following
that are a mystery to me.
Mary encountered this running the sapdb dbt2 cached database workload on her
project machine. The project machine was running 2.6.0-test5-mm3.
This same test passes on the stp machines. But Mary's project machine
has more processors, and more disks, and a different disk controller type.
At this stage, the database has gotten past the database restore phase.
That's where it was failing prior to last night's mm3 patch. Now, the
database itself has been running for about 30 minutes. In the cached
case, much of that first 30 minutes is spent loading the cache.
This Oops seems to have occurred at about the time the database is
transitioning to using its cache. Most of the I/O after this point
is to the log, doing LOTS of sequential writes, with the occasional
random read/write.
Since this machine has more processors, it's doing transactions
more quickly than the same workload on STP machines. So the log write
traffic is probably a lot heavier.
------------[ cut here ]------------
kernel BUG at drivers/block/as-iosched.c:1230!
invalid operand: 0000 [#1]
SMP
CPU: 3
EIP: 0060:[<c0228146>] Not tainted VLI
EFLAGS: 00010046
EIP is at as_dispatch_request+0x236/0x2f0
eax: 00000000 ebx: f7a451a0 ecx: 00000000 edx: 00000000
esi: 00000000 edi: 00000001 ebp: 00000000 esp: f5f67ef8
ds: 007b es: 007b ss: 0068
Process kernel (pid: 2283, threadinfo=f5f66000 task=f62760a0)
Stack: f7a451a0 f5900820 f7a28000 f7a02600 c0235c23 f7a451a0 00000000 f7836000
f5f67fc4 c0228238 f7a451a0 f7a08420 f7836000 c021fbb6 f7836000 f77e0000
f7a28000 f7a08420 f7a28000 c023a128 f7836000 f5f02de0 f77e0090 0000000a
Call Trace:
[<c0235c23>] DAC960_BA_QueueCommand+0x43/0xb0
[<c0228238>] as_next_request+0x38/0x50
[<c021fbb6>] elv_next_request+0x16/0x110
[<c023a128>] DAC960_ProcessRequest+0x38/0x190
[<c023cd40>] DAC960_BA_InterruptHandler+0x90/0xb0
[<c010e899>] handle_IRQ_event+0x49/0x80
[<c010ec0f>] do_IRQ+0x9f/0x150
[<c030cb0c>] common_interrupt+0x18/0x20
[<c030007b>] rpcauth_free_credcache+0xbb/0x100
Code: 43 50 00 00 00 00 8b 43 54 8b 6b 1c c7 43 5c 00 00 00 00 89 43 58 e9 95 fe ff ff c7 43 48 01 00 00 00 c7 43 4c 00 00 00 00 eb d4 <0f> 0b ce 04 fd da 32 c0 eb c7 8b 43 50 e9 61 ff ff ff 0f 0b b6
<0>Kernel panic: Fatal exception in interrupt
In interrupt handler - not syncing
<6>APIC error on CPU3: 00(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
APIC error on CPU3: 08(08)
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linux-2.6-npiggin/drivers/block/as-iosched.c | 21 +++++++++++++++------
1 files changed, 15 insertions(+), 6 deletions(-)
diff -puN drivers/block/as-iosched.c~as-oops-fix drivers/block/as-iosched.c
--- linux-2.6/drivers/block/as-iosched.c~as-oops-fix 2003-09-20 11:13:26.000000000 +1000
+++ linux-2.6-npiggin/drivers/block/as-iosched.c 2003-09-20 11:22:55.000000000 +1000
@@ -1303,7 +1303,7 @@ static struct request *as_next_request(r
* Add arq to a list behind alias
*/
static inline void
-as_add_aliased_request(struct as_rq *arq, struct as_rq *alias)
+as_add_aliased_request(struct as_data *ad, struct as_rq *arq, struct as_rq *alias)
{
/*
* Another request with the same start sector on the rbtree.
@@ -1312,6 +1312,11 @@ as_add_aliased_request(struct as_rq *arq
*/
list_add_tail(&arq->request->queuelist, &alias->request->queuelist);
+ /*
+ * Don't want to have to handle merges.
+ */
+ as_remove_merge_hints(ad->q, arq);
+
}
/*
@@ -1353,7 +1358,7 @@ static void as_add_request(struct as_dat
as_update_arq(ad, arq); /* keep state machine up to date */
} else {
- as_add_aliased_request(arq, alias);
+ as_add_aliased_request(ad, arq, alias);
/*
* have we been anticipating this request?
* or does it come from the same process as the one we are
@@ -1553,8 +1558,10 @@ static void as_merged_request(request_qu
* currently don't bother. Ditto the next function.
*/
as_del_arq_rb(ad, arq);
- if ((alias = as_add_arq_rb(ad, arq)) )
- as_add_aliased_request(arq, alias);
+ if ((alias = as_add_arq_rb(ad, arq)) ) {
+ list_del_init(&arq->fifo);
+ as_add_aliased_request(ad, arq, alias);
+ }
/*
* Note! At this stage of this and the next function, our next
* request may not be optimal - eg the request may have "grown"
@@ -1586,8 +1593,10 @@ as_merged_requests(request_queue_t *q, s
if (rq_rb_key(req) != arq->rb_key) {
struct as_rq *alias;
as_del_arq_rb(ad, arq);
- if ((alias = as_add_arq_rb(ad, arq)) )
- as_add_aliased_request(arq, alias);
+ if ((alias = as_add_arq_rb(ad, arq)) ) {
+ list_del_init(&arq->fifo);
+ as_add_aliased_request(ad, arq, alias);
+ }
}
/*
_