Higher priority for slave thread possible?

[Julien Walther]

Hello everyone,

our setup is a replication scenario with one master and three slaves under MySQL 4.1.11. The slaves are being read in a random way by our application for load balancing purposes.

Due to heavy demand at the moment, the load on the whole cluster increases quickly and continuously, which leads to our slaves lagging from 10 up to 1600(!) seconds behind the master during peak times ('SHOW SLAVE STATUS' => seconds_behind_master).

My question:
Is it possible to give the "slave SQL thread" a higher priority on OS level (e.g. with "renice"), or does MySQL already provide something similar?

Because if we managed to give this thread a higher priority, the execution of "normal" queries would in fact be delayed, but it would lead to a much "better" user experience, as the slaves would not be in de-snyc, leading to strange and uncomprehensible effects for the user.

I'd appreciate any advice in this direction.

Thanks a lot in advance,
Julien