On 2014-11-14 15:59, Meelis Roos wrote:
The second oops is in blk_mq_map_queue() which is a trivial
two level cpu lookup. I wonder if there's something odd about
cpu numbers on these big old sparc systems?
CPU numbers are sparse - they are determined by hardware slot number and
some models only fill every other mainboard slot, and first slots can be
free. I have first board offline and currently have CPUs numbered
10,11,14,15 online.
Here is debug with Jens's patch:
[ 133.971050] CPU 11: synchronized TICK with master CPU (last diff -1 cycles, maxerr 516 cycles)
[ 133.975491] CPU 14: synchronized TICK with master CPU (last diff -3 cycles, maxerr 531 cycles)
[ 133.979943] CPU 15: synchronized TICK with master CPU (last diff -3 cycles, maxerr 531 cycles)
[ 133.980146] Brought up 4 CPUs
So this looks like this might be the issue. On a scsi-mq disabled boot,
you have 4 CPUs, but how are they numbered?
The numbers are always the same.
I would hope so, my question was really on what CPU numbers you see. But
I guess that 10, 11, 14, and 15?
But everything seems to be mapped to queue 0?
As it should, scsi-mq only supports a single hw queue for now.
We might need Christophs debug patch on top this to fully know...
Applied it too, dmesg is below. Yes it does spam the log a lot, and over
9600bps console its' somewhat slow :)
There is another detail to note -this server contains a faulty disk as
sdc that times out spinup. I left it in the server because it helped to
pinpoint and fix a previous error in esp scsi driver. This can be a
factor here too - the error handling details.
It could be. So we have tons of mappings from CPU10 to queue 0, but then
we see this:
[ 256.236742] cpu: 10
[ 256.236749] queue: 809119744
and it turns to crap. This is pretty weird. Try with this debug patch -
get rid of the other ones first. It should reduce your noise level too.
--
Jens Axboe
diff --git a/block/blk-mq-cpumap.c b/block/blk-mq-cpumap.c
index 1065d7c65fa1..9200e2aee746 100644
--- a/block/blk-mq-cpumap.c
+++ b/block/blk-mq-cpumap.c
@@ -81,6 +81,9 @@ int blk_mq_update_queue_map(unsigned int *map, unsigned int nr_queues)
map[i] = map[first_sibling];
}
+ for (i = 0; i < queue; i++)
+ printk(KERN_ERR "cpumap %d -> %d\n", i, map[i]);
+
free_cpumask_var(cpus);
return 0;
}
diff --git a/block/blk-mq.c b/block/blk-mq.c
index 68929bad9a6a..1678da3505ea 100644
--- a/block/blk-mq.c
+++ b/block/blk-mq.c
@@ -1265,12 +1265,25 @@ run_queue:
blk_mq_put_ctx(data.ctx);
}
+static int did_warn;
+
/*
* Default mapping to a software queue, since we use one per CPU.
*/
struct blk_mq_hw_ctx *blk_mq_map_queue(struct request_queue *q, const int cpu)
{
- return q->queue_hw_ctx[q->mq_map[cpu]];
+ int i;
+
+ i = q->mq_map[cpu];
+ if (!i || did_warn)
+ return q->queue_hw_ctx[0];
+
+ printk(KERN_ERR "blk-mq: cpu %u got queue %u\n", cpu, i);
+ for_each_online_cpu(i)
+ printk(KERN_ERR " cpu%d -> queue index %u\n", i, q->mq_map[i]);
+
+ did_warn = 1;
+ return q->queue_hw_ctx[0];
}
EXPORT_SYMBOL(blk_mq_map_queue);
