Hi Joerg, Thanks a lot for the info. regards anandkl
On 7/23/08, Joerg Bruehe <[EMAIL PROTECTED]> wrote: > > Hi ! > > > Ananda Kumar wrote: > >> Hi All, >> I have setup slave db. The machine configuration details of this slave is >> same as master. >> >> OS=redhat >> 8 cpu >> 16GB RAM >> >> key_buffer_size=3000M >> innodb_buffer_pool_size=10000M. >> >> But when i do top, in the master db >> >> >> Cpu(s): 0.5%us, 0.3%sy, 0.0%ni, 87.2%id, 11.9%wa, 0.0%hi, 0.1%si, >> 0.0%st >> Mem: 16436956k total, 16350252k used, 86704k free, 9188k buffers >> Swap: 16386292k total, 37232k used, 16349060k free, 2358944k cached >> >> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND >> 28706 mysql 15 0 14.3g 13g 4688 S 6 84.1 540:21.55 mysqld >> >> On slave db >> >> Cpu(s): 0.7%us, 0.2%sy, 0.0%ni, 87.3%id, 11.8%wa, 0.0%hi, 0.0%si, >> 0.0%st >> Mem: 16436956k total, 16351536k used, 85420k free, 16400k buffers >> Swap: 16386292k total, 164k used, 16386128k free, 4289520k cached >> >> PID USER PR NI VIRT RES SHR S %CPU %MEM TIME+ COMMAND >> 14042 mysql 18 0 14.0g 11g 4652 S 7 72.5 265:08.62 mysqld >> 435 root 10 -5 0 0 0 S 0 0.0 3:29.07 kswapd0 >> >> >> >> As you can see the RES in master is 13g, but on slave its 11G any specific >> reason for this. This is causing some of the sql's on the slave to be >> slower than master for the same select statement on both master and slave. >> > > "RES" is the amount of RAM used by the process, as controlled by the memory > allocation (Linux kernel). > It depends not only on the address space requested by the process, but also > on those by other processes and on the paging / swapping policy (which AFAIK > depends on the which process accesses memory how frequent). > > The MySQL process on the slave has a smaller RES if and only if there is > reason for the Linux kernel to allocate less RAM, this typically means there > are other processes requiring it more urgently. > > *If* the database load on the master is higher, or accesses more data, or > there is less competition about the RAM, it is only natural that RES for the > slave is less. > > > Database performance strongly depends on caching: > If the cache on the master already contains the needed pages, and on the > slave it doesn't, it is normal that the first statement needing them has to > wait for disk I/O and so is slower. > > > Jörg > > -- > Joerg Bruehe, MySQL Build Team, [EMAIL PROTECTED] > Sun Microsystems GmbH, Sonnenallee 1, D-85551 Kirchheim-Heimstetten > Geschaeftsfuehrer: Thomas Schroeder, Wolfgang Engels, Dr. Roland Boemer > Vorsitzender des Aufsichtsrates: Martin Haering Muenchen: HRB161028 > >
