先了解什么是off-cpu
- On-CPU: where threads are spending time running on-CPU.
- Off-CPU: where time is spent waiting while blocked on I/O, locks, timers, paging/swapping, etc.
從上面的意思基本上了解offcputime的意思是什么了:用於測量某一進程被阻塞的時間。
老樣子，還是從help開始說起：
usage: offcputime [-h] [-p PID | -t TID | -u | -k] [-U | -K] [-d] [-f] [--stack-storage-size STACK_STORAGE_SIZE] [-m MIN_BLOCK_TIME] [-M MAX_BLOCK_TIME] [--state STATE] [duration] Summarize off-CPU time by stack trace positional arguments: duration duration of trace, in seconds optional arguments: -h, --help show this help message and exit -p PID, --pid PID trace this PID only #僅僅跟蹤某一進程阻塞時間 -t TID, --tid TID trace this TID only #僅僅跟蹤某一線程阻塞時間 -u, --user-threads-only user threads only (no kernel threads) #僅僅跟蹤用戶態而非內核態線程阻塞時間 -k, --kernel-threads-only kernel threads only (no user threads) #僅僅跟蹤內核態線程阻塞時間 -U, --user-stacks-only show stacks from user space only (no kernel space #僅僅顯示用戶態調用棧關系 stacks) -K, --kernel-stacks-only #僅僅顯示內核態調用棧關系 show stacks from kernel space only (no user space stacks) -d, --delimited insert delimiter between kernel/user stacks #將內核態和用戶態調用棧分割開來 -f, --folded output folded format # 采用折疊模式輸出d --stack-storage-size STACK_STORAGE_SIZE # 設置棧跟蹤過程存儲空間大小 the number of unique stack traces that can be stored and displayed (default 1024) -m MIN_BLOCK_TIME, --min-block-time MIN_BLOCK_TIME #只打印阻塞時間不小於xxx us的進程情況 the amount of time in microseconds over which we store traces (default 1) -M MAX_BLOCK_TIME, --max-block-time MAX_BLOCK_TIME #只打印阻塞時間不大於xxx us的進程情況 the amount of time in microseconds under which we store traces (default U64_MAX) --state STATE filter on this thread state bitmask (eg, 2 == #追蹤進程為某種狀態的阻塞情況，例如不可中斷 TASK_UNINTERRUPTIBLE) see include/linux/sched.h
./offcputime -K
顯示所有進程內核態棧調用情況
schedule schedule_timeout io_schedule_timeout bit_wait_io __wait_on_bit wait_on_page_bit_killable __lock_page_or_retry filemap_fault __do_fault handle_mm_fault __do_page_fault do_page_fault page_fault chmod 13 表示阻塞時間為13us schedule rcu_nocb_kthread kthread ret_from_fork ddebug_tables rcuos/0 22 表示阻塞時間為22us
./offcputime -K -f 5
采用折疊方式顯示棧調用流程
bash;entry_SYSCALL_64_fastpath;sys_read;vfs_read;__vfs_read;tty_read;n_tty_read;call_rwsem_down_read_failed;rwsem_down_read_failed;schedule 8 yes;entry_SYSCALL_64_fastpath;sys_write;vfs_write;__vfs_write;tty_write;n_tty_write;call_rwsem_down_read_failed;rwsem_down_read_failed;schedule 14 run;page_fault;do_page_fault;__do_page_fault;handle_mm_fault;__do_fault;filemap_fault;__lock_page_or_retry;wait_on_page_bit_killable;__wait_on_bit;bit_wait_io;io_schedule_timeout;schedule_timeout;schedule 33 rcuos/4;ret_from_fork;kthread;rcu_nocb_kthread;schedule 45 bash;entry_SYSCALL_64_fastpath;sys_read;vfs_read;__vfs_read;pipe_read;pipe_wait;schedule 88 run;page_fault;do_page_fault;__do_page_fault;handle_mm_fault;__do_fault;filemap_fault;__lock_page_or_retry;wait_on_page_bit_killable;__wait_on_bit;bit_wait_io;io_schedule_timeout;schedule_timeout;schedule 108 jbd2/xvda1-8;mb_cache_list;ret_from_fork;kthread;kjournald2;jbd2_journal_commit_transaction;__wait_on_buffer;out_of_line_wait_on_bit;__wait_on_bit;bit_wait_io;io_schedule_timeout;schedule_timeout;schedule 828 jbd2/xvda1-8;mb_cache_list;ret_from_fork;kthread;kjournald2;jbd2_journal_commit_transaction;__wait_on_buffer;out_of_line_wait_on_bit;__wait_on_bit;bit_wait_io;io_schedule_timeout;schedule_timeout;schedule 6201 supervise;entry_SYSCALL_64_fastpath;sys_rename;dput;__dentry_kill;iput;evict;ext4_evict_inode;truncate_inode_pages_final;truncate_inode_pages_range;wait_on_page_bit;__wait_on_bit;bit_wait_io;io_schedule_timeout;schedule_timeout;schedule 41049 run;entry_SYSCALL_64_fastpath;sys_wait4;do_wait;schedule 120709 bash;entry_SYSCALL_64_fastpath;sys_wait4;do_wait;schedule 699320 us
更多例子
examples: ./offcputime # trace off-CPU stack time until Ctrl-C ./offcputime 5 # trace for 5 seconds only ./offcputime -f 5 # 5 seconds, and output in folded format ./offcputime -m 1000 # trace only events that last more than 1000 usec ./offcputime -M 10000 # trace only events that last less than 10000 usec ./offcputime -p 185 # only trace threads for PID 185 ./offcputime -t 188 # only trace thread 188 ./offcputime -u # only trace user threads (no kernel) ./offcputime -k # only trace kernel threads (no user) ./offcputime -U # only show user space stacks (no kernel) ./offcputime -K # only show kernel space stacks (no user)