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lockstat(1)                                                      lockstat(1)




NAME

       lockstat - report kernel lock and profiling statistics


SYNOPSIS

       lockstat [-ACEHI] [-e event_list] [-i rate]
            [-b | -t | -h | -s depth] [-n nrecords]
            [-l lock [, size]] [-d duration]
            [-f function [, size]] [-T] [-ckgwWRpP] [-D count]
            [-o filename] [-x opt [=val]] command [args]



DESCRIPTION

       The  lockstat utility gathers and displays kernel locking and profiling
       statistics. lockstat allows you to specify which events to  watch  (for
       example,  spin on adaptive mutex, block on read access to rwlock due to
       waiting writers, and so forth) how much data to gather for each  event,
       and  how  to  display  the data. By default, lockstat monitors all lock
       contention events,  gathers  frequency  and  timing  data  about  those
       events,  and  displays  the data in decreasing frequency order, so that
       the most common events appear first.


       lockstat gathers data until the specified command completes. For  exam-
       ple,  to  gather  statistics for a fixed-time interval, use sleep(1) as
       the command, as follows:


       example# lockstat sleep 5


       When the -I option is specified, lockstat establishes  a  per-processor
       high-level  periodic  interrupt  source  to gather profiling data.  The
       interrupt handler simply generates a lockstat event whose caller is the
       interrupted  PC (program counter). The profiling event is just like any
       other lockstat event, so all of the normal lockstat options are  appli-
       cable.


       lockstat relies on DTrace to modify the running kernel's text to inter-
       cept events of interest. This imposes a small but  measurable  overhead
       on  all  system activity, so access to lockstat is restricted to super-
       user by default. The system administrator can permit other users to use
       lockstat  by  granting  them additional DTrace privileges. Refer to the
       Solaris Dynamic Tracing Guide for more information about  DTrace  secu-
       rity features.


OPTIONS

       The following options are supported:

   Event Selection
       If no event selection options are specified, the default is -C.

       -A

           Watch all lock events. -A is equivalent to -CH.


       -C

           Watch contention events.


       -E

           Watch error events.


       -e event_list

           Only  watch  the  specified events. event list is a comma-separated
           list of events or ranges of events such as 1,4-7,35.  Run  lockstat
           with no arguments to get a brief description of all events.


       -H

           Watch hold events.


       -I

           Watch profiling interrupt events.


       -i rate

           Interrupt  rate  (per second) for -I. The default is 97 Hz, so that
           profiling doesn't run in lockstep with the clock  interrupt  (which
           runs at 100 Hz).


   Data Gathering
       -x arg[=val]

           Enable  or modify a DTrace runtime option or D compiler option. The
           list of options is found in the . Boolean options  are  enabled  by
           specifying  their  name.  Options with values are set by separating
           the option name and value with an equals sign (=).


   Data Gathering (Mutually Exclusive)
       -b

           Basic statistics: lock, caller, number of events.


       -h

           Histogram: Timing plus time-distribution histograms.


       -s depth

           Stack trace: Histogram plus stack traces up to depth frames deep.


       -t

           Timing: Basic plus timing for all events [default].


   Data Filtering
       -d duration

           Only watch events longer than duration.


       -f func[,size]

           Only watch events generated by func, which can be  specified  as  a
           symbolic  name or hex address. size defaults to the ELF symbol size
           if available, or 1 if not.


       -l lock[,size]

           Only watch lock, which can be specified as a symbolic name  or  hex
           address.  size  defaults  to the ELF symbol size or 1 if the symbol
           size is not available.


       -n nrecords

           Maximum number of data records.


       -T

           Trace (rather than sample) events [off by default].


   Data Reporting
       -c

           Coalesce lock data for lock arrays (for example, pse_mutex[]).


       -D count

           Only display the top count events of each type.


       -g

           Show total events generated by  function.  For  example,  if  foo()
           calls bar() in a loop, the work done by bar() counts as work gener-
           ated by foo() (along with any work done by foo()  itself).  The  -g
           option  works by counting the total number of stack frames in which
           each function appears.  This  implies  two  things:  (1)  the  data
           reported  by  -g can be misleading if the stack traces are not deep
           enough, and (2) functions that are called  recursively  might  show
           greater than 100% activity. In light of issue (1), the default data
           gathering mode when using -g is -s 50.


       -k

           Coalesce PCs within functions.


       -o filename

           Direct output to filename.


       -P

           Sort data by (count * time) product.


       -p

           Parsable output format.


       -R

           Display rates (events per second) rather than counts.


       -W

           Whichever: distinguish events only by caller, not by lock.


       -w

           Wherever: distinguish events only by lock, not by caller.



DISPLAY FORMATS

       The following headers appear over various columns of data.

       Count or ops/s

           Number of times this event occurred, or the rate (times per second)
           if -R was specified.


       indv

           Percentage of all events represented by this individual event.


       genr

           Percentage of all events generated by this function.


       cuml

           Cumulative percentage; a running total of the individuals.


       rcnt

           Average  reference count. This will always be 1 for exclusive locks
           (mutexes, spin locks, rwlocks held as writer) but  can  be  greater
           than 1 for shared locks (rwlocks held as reader).


       nsec

           Average  duration  of the events in nanoseconds, as appropriate for
           the event.  For  the  profiling  event,  duration  means  interrupt
           latency.


       Lock

           Address of the lock; displayed symbolically if possible.


       CPU

           CPU, reported as cpu[id].


       Caller

           Address of the caller; displayed symbolically if possible.



EXAMPLES

       Example 1 Measuring Kernel Lock Contention

         example# lockstat sleep 5
         Adaptive mutex spin: 2210 events in 5.055 seconds (437 events/sec)



         Count indv cuml rcnt     nsec Lock                Caller
         ------------------------------------------------------------------------
           269  12%  12% 1.00     2160 service_queue       background+0xdc
           249  11%  23% 1.00       86 service_queue       qenable_locked+0x64
           228  10%  34% 1.00      131 service_queue       background+0x15c
            68   3%  37% 1.00       79 0x30000024070       untimeout+0x1c
            59   3%  40% 1.00      384 0x300066fa8e0       background+0xb0
            43   2%  41% 1.00       30 rqcred_lock         svc_getreq+0x3c
            42   2%  43% 1.00      341 0x30006834eb8       background+0xb0
            41   2%  45% 1.00      135 0x30000021058       untimeout+0x1c
            40   2%  47% 1.00       39 rqcred_lock         svc_getreq+0x260
            37   2%  49% 1.00     2372 0x300068e83d0       hmestart+0x1c4
            36   2%  50% 1.00       77 0x30000021058       timeout_common+0x4
            36   2%  52% 1.00      354 0x300066fa120       background+0xb0
            32   1%  53% 1.00       97 0x30000024070       timeout_common+0x4
            31   1%  55% 1.00     2923 0x300069883d0       hmestart+0x1c4
            29   1%  56% 1.00      366 0x300066fb290       background+0xb0
            28   1%  57% 1.00      117 0x3000001e040       untimeout+0x1c
            25   1%  59% 1.00       93 0x3000001e040       timeout_common+0x4
            22   1%  60% 1.00       25 0x30005161110       sync_stream_buf+0xdc
            21   1%  60% 1.00      291 0x30006834eb8       putq+0xa4
            19   1%  61% 1.00       43 0x3000515dcb0       mdf_alloc+0xc
            18   1%  62% 1.00      456 0x30006834eb8       qenable+0x8
            18   1%  63% 1.00       61 service_queue       queuerun+0x168
            17   1%  64% 1.00      268 0x30005418ee8       vmem_free+0x3c
         [...]

         R/W reader blocked by writer: 76 events in 5.055 seconds (15 events/sec)

         Count indv cuml rcnt     nsec Lock                Caller
         ------------------------------------------------------------------------
            23  30%  30% 1.00 22590137 0x300098ba358       ufs_dirlook+0xd0
            17  22%  53% 1.00  5820995 0x3000ad815e8       find_bp+0x10
            13  17%  70% 1.00  2639918 0x300098ba360       ufs_iget+0x198
             4   5%  75% 1.00  3193015 0x300098ba360       ufs_getattr+0x54
             3   4%  79% 1.00  7953418 0x3000ad817c0       find_bp+0x10
             3   4%  83% 1.00   935211 0x3000ad815e8       find_read_lof+0x14
             2   3%  86% 1.00 16357310 0x300073a4720       find_bp+0x10
             2   3%  88% 1.00  2072433 0x300073a4720       find_read_lof+0x14
             2   3%  91% 1.00  1606153 0x300073a4370       find_bp+0x10
             1   1%  92% 1.00  2656909 0x300107e7400       ufs_iget+0x198
         [...]



       Example 2 Measuring Hold Times

         example# lockstat -H -D 10 sleep 1
         Adaptive mutex spin: 513 events



         Count indv cuml rcnt     nsec Lock                Caller
         -------------------------------------------------------------------------
           480   5%   5% 1.00     1136 0x300007718e8       putnext+0x40
           286   3%   9% 1.00      666 0x3000077b430       getf+0xd8
           271   3%  12% 1.00      537 0x3000077b430       msgio32+0x2fc
           270   3%  15% 1.00     3670 0x300007718e8       strgetmsg+0x3d4
           270   3%  18% 1.00     1016 0x300007c38b0       getq_noenab+0x200
           264   3%  20% 1.00     1649 0x300007718e8       strgetmsg+0xa70
           216   2%  23% 1.00     6251 tcp_mi_lock         tcp_snmp_get+0xfc
           206   2%  25% 1.00      602 thread_free_lock    clock+0x250
           138   2%  27% 1.00      485 0x300007c3998       putnext+0xb8
           138   2%  28% 1.00     3706 0x300007718e8       strrput+0x5b8
         -------------------------------------------------------------------------
         [...]



       Example  3  Measuring Hold Times for Stack Traces Containing a Specific
       Function

         example# lockstat -H -f tcp_rput_data -s 50 -D 10 sleep 1
         Adaptive mutex spin: 11 events in 1.023 seconds (11
         events/sec)



         -------------------------------------------------------------------------
         Count indv cuml rcnt     nsec Lock                   Caller
             9  82%  82% 1.00     2540 0x30000031380          tcp_rput_data+0x2b90

               nsec ------ Time Distribution ------ count     Stack
                256 |@@@@@@@@@@@@@@@@               5         tcp_rput_data+0x2b90
                512 |@@@@@@                         2         putnext+0x78
               1024 |@@@                            1         ip_rput+0xec4
               2048 |                               0         _c_putnext+0x148
               4096 |                               0         hmeread+0x31c
               8192 |                               0         hmeintr+0x36c
              16384 |@@@                            1
         sbus_intr_wrapper+0x30
         [...]

         Count indv cuml rcnt     nsec Lock                   Caller
             1   9%  91% 1.00     1036 0x30000055380          freemsg+0x44

               nsec ------ Time Distribution ------ count     Stack
               1024 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@@ 1         freemsg+0x44
                                                              tcp_rput_data+0x2fd0
                                                              putnext+0x78
                                                              ip_rput+0xec4
                                                              _c_putnext+0x148
                                                              hmeread+0x31c
                                                              hmeintr+0x36c

         sbus_intr_wrapper+0x30
         -------------------------------------------------------------------------
         [...]



       Example 4 Basic Kernel Profiling


       For basic profiling, we don't care whether the profiling interrupt sam-
       pled  foo()+0x4c  or foo()+0x78; we care only that it sampled somewhere
       in foo(), so we use -k. The CPU and PIL aren't relevant to  basic  pro-
       filing because we are measuring the system as a whole, not a particular
       CPU or interrupt level, so we use -W.


         example# lockstat -kIW -D 20 ./polltest
         Profiling interrupt: 82 events in 0.424 seconds (194
         events/sec)



         Count indv cuml rcnt     nsec Hottest CPU         Caller
         -----------------------------------------------------------------------
             8  10%  10% 1.00      698 cpu[1]              utl0
             6   7%  17% 1.00      299 master_cpu          read
             5   6%  23% 1.00      124 cpu[1]              getf
             4   5%  28% 1.00      327 master_cpu          fifo_read
             4   5%  33% 1.00      112 cpu[1]              poll
             4   5%  38% 1.00      212 cpu[1]              uiomove
             4   5%  43% 1.00      361 cpu[1]              mutex_tryenter
             3   4%  46% 1.00      682 master_cpu          write
             3   4%  50% 1.00       89 master_cpu          pcache_poll
             3   4%  54% 1.00      118 cpu[1]              set_active_fd
             3   4%  57% 1.00      105 master_cpu          syscall_trap32
             3   4%  61% 1.00      640 cpu[1]              (usermode)
             2   2%  63% 1.00      127 cpu[1]              fifo_poll
             2   2%  66% 1.00      300 cpu[1]              fifo_write
             2   2%  68% 1.00      669 master_cpu          releasef
             2   2%  71% 1.00      112 cpu[1]              bt_getlowbit
             2   2%  73% 1.00      247 cpu[1]              splx
             2   2%  76% 1.00      503 master_cpu          mutex_enter
             2   2%  78% 1.00      467 master_cpu          disp_lock_enter
             2   2%  80% 1.00      139 cpu[1]              default_copyin
         -----------------------------------------------------------------------
         [...]



       Example 5 Generated-load Profiling


       In the example above, 5% of the samples were in poll(). This  tells  us
       how  much  time  was  spent  inside poll() itself, but tells us nothing
       about how much work was generated by poll(); that is, how much time  we
       spent  in  functions called by poll(). To determine that, we use the -g
       option. The example below shows that although polltest spends  only  5%
       of  its  time in poll() itself, poll()-induced work accounts for 34% of
       the load.



       Note that the functions that generate the  profiling  interrupt  (lock-
       stat_intr(),  cyclic_fire(), and so forth) appear in every stack trace,
       and therefore are considered to have generated 100% of the load.   This
       illustrates  an  important point: the generated load percentages do not
       add up to 100% because they are not independent. If 72%  of  all  stack
       traces  contain both foo() and bar(), then both foo() and bar() are 72%
       load generators.


         example# lockstat -kgIW -D 20 ./polltest
         Profiling interrupt: 80 events in 0.412 seconds (194 events/sec)



         Count genr cuml rcnt     nsec Hottest CPU         Caller
         -------------------------------------------------------------------------
            80 100% ---- 1.00      310 cpu[1]              lockstat_intr
            80 100% ---- 1.00      310 cpu[1]              cyclic_fire
            80 100% ---- 1.00      310 cpu[1]              cbe_level14
            80 100% ---- 1.00      310 cpu[1]              current_thread
            27  34% ---- 1.00      176 cpu[1]              poll
            20  25% ---- 1.00      221 master_cpu          write
            19  24% ---- 1.00      249 cpu[1]              read
            17  21% ---- 1.00      232 master_cpu          write32
            17  21% ---- 1.00      207 cpu[1]              pcache_poll
            14  18% ---- 1.00      319 master_cpu          fifo_write
            13  16% ---- 1.00      214 cpu[1]              read32
            10  12% ---- 1.00      208 cpu[1]              fifo_read
            10  12% ---- 1.00      787 cpu[1]              utl0
             9  11% ---- 1.00      178 master_cpu          pcacheset_resolve
             9  11% ---- 1.00      262 master_cpu          uiomove
             7   9% ---- 1.00      506 cpu[1]              (usermode)
             5   6% ---- 1.00      195 cpu[1]              fifo_poll
             5   6% ---- 1.00      136 cpu[1]              syscall_trap32
             4   5% ---- 1.00      139 master_cpu          releasef
             3   4% ---- 1.00      277 cpu[1]              polllock
         -------------------------------------------------------------------------
         [...]



       Example 6 Gathering Lock Contention and Profiling Data for  a  Specific
       Module


       In  this example we use the -f option not to specify a single function,
       but rather to specify the entire text space  of  the  sbus  module.  We
       gather both lock contention and profiling statistics so that contention
       can be correlated with overall load on the module.


         example# modinfo | grep sbus
          24 102a8b6f   b8b4  59   1  sbus (SBus (sysio) nexus driver)



         example# lockstat -kICE -f 0x102a8b6f,0xb8b4 sleep 10
         Adaptive mutex spin: 39 events in 10.042 seconds (4 events/sec)



         Count indv cuml rcnt     nsec Lock               Caller
         -------------------------------------------------------------------------
            15  38%  38% 1.00      206 0x30005160528      sync_stream_buf
             7  18%  56% 1.00       14 0x30005160d18      sync_stream_buf
             6  15%  72% 1.00       27 0x300060c3118      sync_stream_buf
             5  13%  85% 1.00       24 0x300060c3510      sync_stream_buf
             2   5%  90% 1.00       29 0x300060c2d20      sync_stream_buf
             2   5%  95% 1.00       24 0x30005161cf8      sync_stream_buf
             1   3%  97% 1.00       21 0x30005161110      sync_stream_buf
             1   3% 100% 1.00       23 0x30005160130      sync_stream_buf
         [...]

         Adaptive mutex block: 9 events in 10.042 seconds (1 events/sec)

         Count indv cuml rcnt     nsec Lock               Caller
         -------------------------------------------------------------------------
             4  44%  44% 1.00   156539 0x30005160528      sync_stream_buf
             2  22%  67% 1.00   763516 0x30005160d18      sync_stream_buf
             1  11%  78% 1.00   462130 0x300060c3510      sync_stream_buf
             1  11%  89% 1.00   288749 0x30005161110      sync_stream_buf
             1  11% 100% 1.00  1015374 0x30005160130      sync_stream_buf
         [...]

         Profiling interrupt: 229 events in 10.042 seconds (23 events/sec)

         Count indv cuml rcnt     nsec Hottest CPU        Caller

         -------------------------------------------------------------------------
            89  39%  39% 1.00      426 master_cpu         sync_stream_buf
            64  28%  67% 1.00      398 master_cpu         sbus_intr_wrapper
            23  10%  77% 1.00      324 master_cpu         iommu_dvma_kaddr_load
            21   9%  86% 1.00      512 master_cpu         iommu_tlb_flush
            14   6%  92% 1.00      342 master_cpu         iommu_dvma_unload
            13   6%  98% 1.00      306 cpu[1]             iommu_dvma_sync
             5   2% 100% 1.00      389 cpu[1]             iommu_dma_bindhdl
         -------------------------------------------------------------------------
         [...]



       Example 8 Determining which Subsystem is Causing the System to be Busy

         example# lockstat -s 10 -I sleep 20

         Profiling interrupt: 4863 events in 47.375 seconds (103 events/sec)

         Count indv cuml rcnt     nsec CPU              Caller

         -----------------------------------------------------------------------
         1929   40%  40% 0.00     3215 master_cpu       usec_delay+0x78
           nsec ------ Time Distribution ------ count   Stack
           4096 |@@@@@@@@@@@@@@@@@@@@@@@@@@@@@  1872    ata_wait+0x90
           8192 |                               27      acersb_get_intr_status+0x34
          16384 |                               29      ata_set_feature+0x124
          32768 |                               1       ata_disk_start+0x15c
                                                        ata_hba_start+0xbc
                                                        ghd_waitq_process_and \
                                                        _mutex_hold+0x70
                                                        ghd_waitq_process_and \
                                                        _mutex_exit+0x4
                                                        ghd_transport+0x12c
                                                        ata_disk_tran_start+0x108
         -----------------------------------------------------------------------
         [...]




SEE ALSO

       dtrace(1M), plockstat(1M)


       Solaris Dynamic Tracing Guide


NOTES

       The profiling support provided by lockstat -I  replaces  the  old  (and
       undocumented) /usr/bin/kgmon and /dev/profile.


       Tail-call elimination can affect call sites. For example, if foo()+0x50
       calls bar() and the last thing bar() does  is  call  mutex_exit(),  the
       compiler  can  arrange for bar() to branch to mutex_exit()with a return
       address of foo()+0x58. Thus, the mutex_exit() in bar() will  appear  as
       though it occurred at foo()+0x58.


       The  PC  in  the  stack frame in which an interrupt occurs can be bogus
       because, between function calls, the compiler is free to use the return
       address register for local storage.


       When using the -I and -s options together, the interrupted PC will usu-
       ally not appear anywhere in the stack since the  interrupt  handler  is
       entered asynchronously, not by a function call from that PC.


       The  lockstat  technology is provided on an as-is basis. The format and
       content of lockstat output reflect the current Darwin kernel  implemen-
       tation and are therefore subject to change in future releases.



                                 Jan 27, 2014                     lockstat(1)

OS X 10.10 - Generated Thu Oct 30 07:41:17 CDT 2014
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