Messages in this thread | | | Date | Thu, 8 Nov 2001 10:03:52 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: [patch] scheduler cache affinity improvement for 2.4 kernels |
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On Thu, 8 Nov 2001, Ingo Molnar wrote:
> > Davide, > > On Thu, 8 Nov 2001, Davide Libenzi wrote: > > > Maybe you missed this : > > > > http://www.xmailserver.org/linux-patches/mss.html > > > > where the patch that does this is here : > > > > http://www.xmailserver.org/linux-patches/lnxsched.html#CPUHist > > i'm not sure what the patch is trying to achieve, but this part of > mcsched-2.4.13-0.4.diff looks incorrect: > > + prev->cpu_jtime += (jiffies - prev->sched_jtime) + jiffies; > > (this is "2*jiffies - prev->sched_jtime" which doesnt appear to make much > sense - does it?)
The optimization is not good ( i left it in that way to make it more clear what that operation is meant ) but the mean of the code is ok. It sets the time ( in jiffies ) at which the process won't have any more scheduling advantage.
> and your patch adds a scheduling advantage to processes with more cache > footprint, which is the completely opposite of what we want.
It is exactly what we want indeed : <quote> it's a fix for a UP and SMP scheduler problem Alan described to me recently, the 'CPU intensive process scheduling' problem. The essence of the problem: if there are multiple, CPU-intensive processes running, intermixed with other scheduling activities such as interactive work or network-intensive applications, then the Linux scheduler does a poor job of affinizing processes to processor caches. Such scheduler workload is common for a large percentage of important application workloads: database server workloads, webserver workloads and math-intensive clustered jobs, and other applications. </quote>
and if you take a look at the LatSched sampling it is achived very well.
> but in any case, changing the goodness() function was not a goal of my > patch, i change the granularity of how processes lose their 'effective > priority'.
I'll test the patch asap with the LatSched sampler and i'll let you know.
- Davide
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