Re: [RFC][PATCH] O(1) Entitlement Based Scheduler

From: Shailabh Nagar
Date: Thu Feb 26 2004 - 15:43:53 EST


Mike Fedyk wrote:

Shailabh Nagar wrote:

Mike Fedyk wrote:

Better would be to have the kernel tell the daemon whenever a process in exec-ed, and you have simplicity in the kernel, and policy in user space.




As it turns out, one can still use a fairly simple in-kernel module which provides a *mechanism* for effectively changing a process' entitlement while retaining the policy component in userland.


How much code could be removed if CKRM triggered a userspace process to perform the operations required?


In CKRM, the code to perform classification is an optional kernel module. So size isn't really an issue in terms of impact to core kernel code.

Our prototype version of the classification engine, RBCE, is about 2700 lines without any effort being put into reducing its size etc. If that were to be completely pared down to only provide events to userspace, it would come down by quite a bit (can't say exactly how much but atleast 50% is a safe bet).

I think the more important question is performance impact - what do you give up in terms of efficiency and granularity of control by going to userspace vs what you gain in reduced kernel pathlength. Empirically, we found RBCE was quite efficient but no quantitative analysis was done.

-- Shailabh







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