mysqladmin在SuSE linux系统中--sleep參数使用不准确问题

Posted 2020-06-11

我们都知道，在mysql中。能够使用mysqladmin命令的extended-status选项来查看MySQL的执行状态，比方获取我们经常关注的几个值：

# mysqladmin -uroot -proot ext |grep "Questions\|Queries\|Innodb_rows\|Com_select \|Com_insert \|Com_update \|Com_delete "
| Com_delete                               | 26750       |
| Com_insert                               | 347420      |
| Com_select                               | 1341126     |
| Com_update                               | 454425      |
| Innodb_rows_deleted                      | 26590       |
| Innodb_rows_inserted                     | 347416      |
| Innodb_rows_read                         | 2964050     |
| Innodb_rows_updated                      | 695605      |
| Queries                                  | 2304578     |
| Questions                                | 2259777     |

但这样得到的数值都累计的。假设想了解当前的状态。则须要进行一次差值计算。而庆幸的是，这个client工具提供了两个參数，这样就能实时的得到当前数据库的相关參数值：

-i, --sleep=#       Execute commands again and again with a sleep between，单位是秒

-r, --relative        Show difference between current and previous values when
                                      used with -i. Currently works only with extended-status.

# mysqladmin -uroot -proot ext -i 1 -r |grep "Questions\|Queries\|Innodb_rows\|Com_select \|Com_insert \|Com_update \|Com_delete "
| Com_delete                               | 26750       |
| Com_insert                               | 347420      |
| Com_select                               | 1341129     |
| Com_update                               | 454425      |
| Innodb_rows_deleted                      | 26590       |
| Innodb_rows_inserted                     | 347416      |
| Innodb_rows_read                         | 2964050     |
| Innodb_rows_updated                      | 695605      |
| Queries                                  | 2304592     |
| Questions                                | 2259791     |

这样就得到了MySQL当前数据库每秒中相应值。非常直观，这个命令在RHEL 6.4 x86_64系统上能够正常使用。但在SuSE linux 11sp1 x86_64系统中，却是不准确的。即使用-i（或--sleep=）指定刷新的秒数，但事实并不是如此。

在測试中。常常是指定了--sleep=1，但显示结果却是大概1分多钟刷新一次，很奇怪。但在使用strace跟踪发现了原因：

# strace mysqladmin -uroot -proot ext -i 1 -r |grep "Questions\|Queries\|Innodb_rows\|Com_select \|Com_insert \|Com_update \|Com_delete "
execve("/usr/bin/mysqladmin", ["mysqladmin", "-uroot", "-proot", "ext", "-i", "1", "-r"], [/* 59 vars */]) = 0
brk(0)                                  = 0x62a000
mmap(NULL, 4096, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_ANONYMOUS, -1, 0) = 0x7f0c036fe000
access("/etc/ld.so.preload", R_OK)      = -1 ENOENT (No such file or directory)
open("/usr/lib64/mysql/tls/x86_64/libmysqlclient.so.15", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/usr/lib64/mysql/tls/x86_64", 0x7fffbb00c0f0) = -1 ENOENT (No such file or directory)
open("/usr/lib64/mysql/tls/libmysqlclient.so.15", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/usr/lib64/mysql/tls", 0x7fffbb00c0f0) = -1 ENOENT (No such file or directory)
open("/usr/lib64/mysql/x86_64/libmysqlclient.so.15", O_RDONLY) = -1 ENOENT (No such file or directory)
stat("/usr/lib64/mysql/x86_64", 0x7fffbb00c0f0) = -1 ENOENT (No such file or directory)
open("/usr/lib64/mysql/libmysqlclient.so.15", O_RDONLY) = 3
read(3, "\177ELF\2\1\1\0\0\0\0\0\0\0\0\0\3\0>\0\1\0\0\0\300\262\1\0\0\0\0\0"..., 832) = 832
fstat(3, {st_mode=S_IFREG|0755, st_size=1420448, ...}) = 0
mmap(NULL, 3521032, PROT_READ|PROT_EXEC, MAP_PRIVATE|MAP_DENYWRITE, 3, 0) = 0x7f0c03185000
fadvise64(3, 0, 3521032, POSIX_FADV_WILLNEED) = 0
mprotect(0x7f0c032ac000, 2093056, PROT_NONE) = 0
mmap(0x7f0c034ab000, 217088, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_DENYWRITE, 3, 0x126000) = 0x7f0c034ab000
mmap(0x7f0c034e0000, 2568, PROT_READ|PROT_WRITE, MAP_PRIVATE|MAP_FIXED|MAP_ANONYMOUS, -1, 0) = 0x7f0c034e0000
close(3)                                = 0
……  <==== 省略若干 ====>
write(1, "+-------------------------------"..., 4096) = 4096
write(1, "                  | 0           "..., 4096) = 4096
write(1, "       |\n| Com_truncate         "..., 4096) = 4096
write(1, "ze                         | 163"..., 4096) = 4096
rt_sigprocmask(SIG_BLOCK, [CHLD], [], 8) = 0
rt_sigaction(SIGCHLD, NULL, {SIG_DFL, [], 0}, 8) = 0
rt_sigprocmask(SIG_SETMASK, [], NULL, 8) = 0
<span style="color:#ff0000;">nanosleep({83, 0}</span>,| Com_delete                               | 26750       |
| Com_insert                               | 347420      |
| Com_select                               | 1341136     |
| Com_update                               | 454425      |
| Innodb_rows_deleted                      | 26590       |
| Innodb_rows_inserted                     | 347416      |
| Innodb_rows_read                         | 2964050     |
| Innodb_rows_updated                      | 695605      |
| Queries                                  | 2304622     |
| Questions                                | 2259821     |

问题就在即使指定的是1秒刷新，但系统调用时却是83s刷新一次：

nanosleep({83, 0}

非常可惜。这个功能不在这个系统中使用。更不幸的时。生产环境中的全都SuSE linux 11sp1系统，郁闷......

准备找个机会，向SUSE原厂问一下，究竟什么情况的。