Messages in this thread | | | Date | Tue, 23 Aug 2005 13:10:04 -0700 (PDT) | From | Danial Thom <> | Subject | Re: 2.6.12 Performance problems |
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--- Sven-Thorsten Dietrich <sven@mvista.com> wrote:
> On Tue, 2005-08-23 at 10:10 -0700, Danial Thom > wrote: > > > > > > >Ok, well you'll have to explain this one: > > > > > > > >"Low latency comes at the cost of > decreased > > > >throughput - can't have both" > > > > > > > > > > > Configuring "preempt" gives lower latency, > > > because then > > > almost anything can be interrupted > (preempted). > > > You can then > > > get very quick responses to some things, > i.e. > > > interrupts and such. > > > > I think part of the problem is the continued > > misuse of the word "latency". Latency, in > > language terms, means "unexplained delay". > > latency > > n > 1: (computer science) the time it takes for a > specific block of data on > a data track to rotate around to the read/write > head [syn: rotational > latency] > 2: the time that elapses between a stimulus and > the response to it [syn: > reaction time, response time, latent period] > 3: the state of being not yet evident or active > > No apparent references to "unexplained" in > association with the word > latency.
Teaching English is not my thing, but latent means "dormant", which means doing nothing. So the time it takes to perform a task is not latency. Its the time it really takes compared to the time it ought to take if there was no overhead. If you have a perfect implementation then you have no latency. Your definition implies that there is no way to have zero latency, which is just wrong.
I've seen computer dictionaries that define latency as the time it takes to get a response. That would mean a network switch's latency is different with different sized packets, which is just plain stupid.
None of this is helpful, but since no one has been able to tell me how to tune it to provide absolute priority to the network stack I'll assume it can't be done.
DT
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