From 417b8d4ac868cf58d6c68f52d72f7648413e0edc Mon Sep 17 00:00:00 2001 From: Dan Williams Date: Fri, 16 Oct 2009 16:25:22 +1100 Subject: md/raid456: downlevel multicore operations to raid_run_ops The percpu conversion allowed a straightforward handoff of stripe processing to the async subsytem that initially showed some modest gains (+4%). However, this model is too simplistic and leads to stripes bouncing between raid5d and the async thread pool for every invocation of handle_stripe(). As reported by Holger this can fall into a pathological situation severely impacting throughput (6x performance loss). By downleveling the parallelism to raid_run_ops the pathological stripe_head bouncing is eliminated. This version still exhibits an average 11% throughput loss for: mdadm --create /dev/md0 /dev/sd[b-q] -n 16 -l 6 echo 1024 > /sys/block/md0/md/stripe_cache_size dd if=/dev/zero of=/dev/md0 bs=1024k count=2048 ...but the results are at least stable and can be used as a base for further multicore experimentation. Reported-by: Holger Kiehl Signed-off-by: Dan Williams Signed-off-by: NeilBrown --- drivers/md/raid5.h | 12 +++++++++++- 1 file changed, 11 insertions(+), 1 deletion(-) (limited to 'drivers/md/raid5.h') diff --git a/drivers/md/raid5.h b/drivers/md/raid5.h index 2390e0e83da..dcefdc9629e 100644 --- a/drivers/md/raid5.h +++ b/drivers/md/raid5.h @@ -214,12 +214,20 @@ struct stripe_head { int disks; /* disks in stripe */ enum check_states check_state; enum reconstruct_states reconstruct_state; - /* stripe_operations + /** + * struct stripe_operations * @target - STRIPE_OP_COMPUTE_BLK target + * @target2 - 2nd compute target in the raid6 case + * @zero_sum_result - P and Q verification flags + * @request - async service request flags for raid_run_ops */ struct stripe_operations { int target, target2; enum sum_check_flags zero_sum_result; + #ifdef CONFIG_MULTICORE_RAID456 + unsigned long request; + wait_queue_head_t wait_for_ops; + #endif } ops; struct r5dev { struct bio req; @@ -294,6 +302,8 @@ struct r6_state { #define STRIPE_FULL_WRITE 13 /* all blocks are set to be overwritten */ #define STRIPE_BIOFILL_RUN 14 #define STRIPE_COMPUTE_RUN 15 +#define STRIPE_OPS_REQ_PENDING 16 + /* * Operation request flags */ -- cgit v1.2.3-18-g5258