LINUX block I/O --systemtap

http://hushi55.github.io/2015/10/16/Block-Input-Output/

http://myaut.github.io/dtrace-stap-book/kernel/bio.html

http://blog.itpub.net/15480802/viewspace-762765/

http://blog.163.com/digoal@126/blog/static/1638770402013101993142404/

http://www.searchtb.com/2013/02/iowait_why_and_optimization.html

http://blog.yufeng.info/ppt

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systemtap 提供的io tracepoint

ioblock.end
ioblock.request
ioblock_trace.bounce
ioblock_trace.end
ioblock_trace.request

ioscheduler.elv_add_request
ioscheduler.elv_add_request.kp
ioscheduler.elv_add_request.tp
ioscheduler.elv_completed_request
ioscheduler.elv_next_request
ioscheduler.elv_next_request.return

ioscheduler_trace.elv_abort_request
ioscheduler_trace.elv_completed_request
ioscheduler_trace.elv_issue_request
ioscheduler_trace.elv_requeue_request
ioscheduler_trace.plug
ioscheduler_trace.unplug_io
ioscheduler_trace.unplug_timer

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[root@localhost ~]# mount   -t  debugfs none  /sys/kernel/debug/
[root@localhost ~]# blktrace  /dev/sda                         
^CDevice: /dev/sda
  CPU  0:                    0 events,      524 KiB data
  CPU  1:                    0 events,      830 KiB data
  Total:                     0 events (dropped 0),     1353 KiB data

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[root@localhost ~]# stap -l 'ioblock.*'
ioblock.end
ioblock.request

[root@localhost ~]# stap -L 'ioblock.*'                    
ioblock.end

name:string devname:string ino:long bytes_done:long error:long sector:long flags:long rw:long vcnt:long

idx:long phys_segments:long hw_segments:long size:long $bio:struct bio* $error:int

ioblock.request

name:string devname:string ino:long sector:long flags:long rw:long vcnt:long idx:long phys_segments:long

hw_segments:long size:long bdev:long bdev_contains:long p_start_sect:long $bio:struct bio*

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[root@localhost ~]# stap -l 'ioscheduler.*'
ioscheduler.elv_add_request
ioscheduler.elv_completed_request
ioscheduler.elv_next_request

[root@localhost ~]# stap -L 'ioscheduler.*'

ioscheduler.elv_add_request

__tracepoint_arg_q:long __tracepoint_arg_rq:long name:string q:long elevator_name:string rq:long disk_major:long disk_minor:long rq_flags:long $q:struct request_queue* $rq:struct request*

ioscheduler.elv_completed_request

name:string elevator_name:string disk_major:long disk_minor:long rq:long rq_flags:long $q:struct request_queue* $rq:struct request*
ioscheduler.elv_next_request

name:string elevator_name:string $q:struct request_queue* $__func__:char[] const

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[root@localhost linux-2.6.32]# stap -l 'kernel.trace("block_*")'
kernel.trace("block:block_bio_backmerge")
kernel.trace("block:block_bio_bounce")
kernel.trace("block:block_bio_complete")
kernel.trace("block:block_bio_frontmerge")
kernel.trace("block:block_bio_queue")
kernel.trace("block:block_getrq")
kernel.trace("block:block_plug")
kernel.trace("block:block_remap")
kernel.trace("block:block_rq_abort")
kernel.trace("block:block_rq_complete")
kernel.trace("block:block_rq_insert")
kernel.trace("block:block_rq_issue")
kernel.trace("block:block_rq_remap")
kernel.trace("block:block_rq_requeue")
kernel.trace("block:block_sleeprq")
kernel.trace("block:block_split")
kernel.trace("block:block_unplug_io")
kernel.trace("block:block_unplug_timer")

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[root@localhost linux-2.6.32]# stap -L 'kernel.trace("block_*")'
kernel.trace("block:block_bio_backmerge") $q:struct request_queue* $bio:struct bio*
kernel.trace("block:block_bio_bounce") $q:struct request_queue* $bio:struct bio*
kernel.trace("block:block_bio_complete") $q:struct request_queue* $bio:struct bio*
kernel.trace("block:block_bio_frontmerge") $q:struct request_queue* $bio:struct bio*
kernel.trace("block:block_bio_queue") $q:struct request_queue* $bio:struct bio*
kernel.trace("block:block_getrq") $q:struct request_queue* $bio:struct bio* $rw:int
kernel.trace("block:block_plug") $q:struct request_queue*
kernel.trace("block:block_remap") $q:struct request_queue* $bio:struct bio* $dev:dev_t $from:sector_t
kernel.trace("block:block_rq_abort") $q:struct request_queue* $rq:struct request*
kernel.trace("block:block_rq_complete") $q:struct request_queue* $rq:struct request*
kernel.trace("block:block_rq_insert") $q:struct request_queue* $rq:struct request*
kernel.trace("block:block_rq_issue") $q:struct request_queue* $rq:struct request*
kernel.trace("block:block_rq_remap") $q:struct request_queue* $rq:struct request* $dev:dev_t $from:sector_t
kernel.trace("block:block_rq_requeue") $q:struct request_queue* $rq:struct request*
kernel.trace("block:block_sleeprq") $q:struct request_queue* $bio:struct bio* $rw:int
kernel.trace("block:block_split") $q:struct request_queue* $bio:struct bio* $new_sector:unsigned int
kernel.trace("block:block_unplug_io") $q:struct request_queue*
kernel.trace("block:block_unplug_timer") $q:struct request_queue*

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[root@localhost linux-2.6.32]# stap -l 'kernel.function("congestion_wait")'
kernel.function("congestion_wait@mm/backing-dev.c:752")

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[root@localhost /]# cd /usr/share/systemtap/tapset

root@localhost tapset]# grep -e 'ioblock.request' -R *   // 在当前目录下文件中搜索 ioblock.request 字符串
ioblock.stp: *  probe ioblock.request - Fires whenever making a generic block I/O request.
ioblock.stp:probe ioblock.request = kernel.function ("generic_make_request")
ioblock.stp:    name = "ioblock.request"

[root@localhost tapset]# stap -l 'kernel.function ("generic_make_request")'
kernel.function("generic_make_request@block/blk-core.c:1502")

[root@localhost tapset]# grep -e 'ioblock.end' -R *
ioblock.stp: * probe ioblock.end - Fires whenever a block I/O transfer is complete.
ioblock.stp:probe ioblock.end = kernel.function("bio_endio")
ioblock.stp:    name = "ioblock.end"

[root@localhost tapset]# stap -l 'kernel.function("bio_endio")'
kernel.function("bio_endio@fs/bio.c:1411")

ioblock.request：是内核函数 generic_make_request 的别名

ioblock.end：是内核函数 bio_endio 的别名

我这是使用的源码安装的 systemtap，

使用 yum 安装的 systemtap 的两个重要位置在

/usr/share/doc/systemtap-client-2.6/examples：systemtap 自带示例脚本的目录

/usr/share/systemtap/：systemtap 运行时的一些脚本，包括一些别名的定义

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用tgpt

(gdb) trace generic_make_request

(gdb) list  1502    //直接显示第 1502行函数generic_make_request 源代码

也可进行实时调试