High Spin Rounds

Dear all:
we are runing mysql 5.1.37 on linux.
The conditions of our db server is below:
CPU: 16 cpu
processor : 1

processor : 15
vendor_id : GenuineIntel
cpu family : 6
model : 26
model name : Intel® Xeon® CPU E5520 @ 2.27GHz
stepping : 5
cpu MHz : 2266.831
cache size : 8192 KB
physical id : 1
siblings : 8
core id : 3
cpu cores : 4
apicid : 23
fpu : yes
fpu_exception : yes
cpuid level : 11
wp : yes
flags : fpu vme de pse tsc msr pae mce cx8 apic sep mtrr pge mca cmov pat pse36 clflush dts acpi mmx fxsr sse sse2 ss ht tm syscall nx rdtscp lm constant_tsc ida pni monitor ds_cpl vmx est tm2 cx16 xtpr popcnt lahf_lm
bogomips : 4533.43
clflush size : 64
cache_alignment : 64
address sizes : 40 bits physical, 48 bits virtual
power management:

total used free shared buffers cached
Mem: 49433700 47088364 2345336 0 273296 14019244
-/+ buffers/cache: 32795824 16637876
Swap: 8385920 0 8385920

Filesystem Size Used Avail Use% Mounted on
/dev/sda1 5.9G 793M 4.8G 15% /
/dev/sda6 237G 71G 154G 32% /opt
/dev/sda3 7.8G 722M 6.7G 10% /var
/dev/sda5 12G 3.0G 8.1G 28% /usr
/dev/sdb1 1.4T 201G 1.1T 16% /DATA
tmpfs 24G 2.0M 24G 1% /dev/shm

our system have high concurrency and is I/O -bound.

From show innodb status,i get following info:


OS WAIT ARRAY INFO: reservation count 220811806, signal count 189985852
Mutex spin waits 0, rounds 117773990214, OS waits 121410990
RW-shared spins 173303537, OS waits 27495328; RW-excl spins 261758434, OS waits 31789867

My question is below:
1)I know innodb using multiphase wait poliy,but i cannt’ understand what does the spin wait/spit rounds/os wait mean?
and why the rounds value is so high but spin wait is zero

  1. can somebody tell me the difference of innodb_sync_spin_loops
    and innodb_thread_sleep_dealy

  2. Just as i have introduced,what 's the best value for innodb_thread_concurrency,does 0 is a good choice!


Take a look at Peter’s explanations here:
http://www.mysqlperformanceblog.com/2006/07/17/show-innodb-s tatus-walk-through/

Thanks for your reply ,fristly!I have read the article you mentioned and the related content in <>,but all of them doesn’t metion what [spin rounds] mean!And the questions i issued still confuse me!

I thind spin wait and spin rounds tell the same thing,but why the value of spin wait is 0 but spin rounds is so huge!