SQMS versus MQMS
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From: Peter Olcott on 14 Apr 2010 20:11 Single Queue Multi Server (SQMS ) versus Multi Queue Multi Server (MQMS) http://users.crhc.illinois.edu/nicol/ece541/slides/queueing.pdf I am not a math guy, I am a computer science guy. I need to know exactly what it is about a SQMS that makes it so much more efficient than a MQMS as shown on slide 31 of the above link. For example is it that the SQ more uniformly distributes the jobs than the MQ, thus reducing idle time? Thanks.
From: Henry on 14 Apr 2010 20:49 On 15/04/2010 01:11, Peter Olcott wrote: > Single Queue Multi Server (SQMS ) versus Multi Queue Multi > Server (MQMS) > http://users.crhc.illinois.edu/nicol/ece541/slides/queueing.pdf > > I am not a math guy, I am a computer science guy. I need to > know exactly what it is about a SQMS that makes it so much > more efficient than a MQMS as shown on slide 31 of the above > link. > > For example is it that the SQ more uniformly distributes the > jobs than the MQ, thus reducing idle time? > > Thanks. > It is because with m M/M/1 queues you will often get some waiting in a number of queues while other servers are idle. That does not happen with one M/M/m queue where idle time only happens when there is no waiting. With real people in queues, this would lead to some of them changing queues, which would then equalise mean response times, though there would still be higher variance of response times with the m queue version.
From: Jasen Betts on 15 Apr 2010 05:16 On 2010-04-15, Peter Olcott <NoSpam(a)OCR4Screen.com> wrote: > Single Queue Multi Server (SQMS ) versus Multi Queue Multi > Server (MQMS) > http://users.crhc.illinois.edu/nicol/ece541/slides/queueing.pdf > > I am not a math guy, I am a computer science guy. I need to > know exactly what it is about a SQMS that makes it so much > more efficient than a MQMS as shown on slide 31 of the above > link. > > For example is it that the SQ more uniformly distributes the > jobs than the MQ, thus reducing idle time? suppose you are in a queue and the job in front of you is a longer than usual one. If there's only one server at the head of the queue you're in for a wait, if there are multiple servers one of the other server will likely be free soon enough For this reason SQMS outperforms MQMS on a least-sqares wait-time test. --- news://freenews.netfront.net/ - complaints: news(a)netfront.net ---
From: Peter Olcott on 15 Apr 2010 09:16 "Jasen Betts" <jasen(a)xnet.co.nz> wrote in message news:hq6lh5$k98$1(a)reversiblemaps.ath.cx... > On 2010-04-15, Peter Olcott <NoSpam(a)OCR4Screen.com> wrote: >> Single Queue Multi Server (SQMS ) versus Multi Queue >> Multi >> Server (MQMS) >> >> http://users.crhc.illinois.edu/nicol/ece541/slides/queueing.pdf >> >> I am not a math guy, I am a computer science guy. I need >> to >> know exactly what it is about a SQMS that makes it so >> much >> more efficient than a MQMS as shown on slide 31 of the >> above >> link. >> >> For example is it that the SQ more uniformly distributes >> the >> jobs than the MQ, thus reducing idle time? > > suppose you are in a queue and the job in front of you is > a longer > than usual one. If there's only one server at the head of > the queue > you're in for a wait, > > if there are multiple servers one of the other server will > likely be > free soon enough This is multiple servers provided on a single CPU, using time slicing. Because of this the more servers there are the slower that each server is. > > For this reason SQMS outperforms MQMS on a least-sqares > wait-time test. > > > > --- news://freenews.netfront.net/ - complaints: > news(a)netfront.net ---
From: Peter Olcott on 15 Apr 2010 09:23
"Henry" <se16(a)btinternet.com> wrote in message news:TZKdna2IBNo9_1vWnZ2dnUVZ8jOdnZ2d(a)bt.com... > On 15/04/2010 01:11, Peter Olcott wrote: >> Single Queue Multi Server (SQMS ) versus Multi Queue >> Multi >> Server (MQMS) >> >> http://users.crhc.illinois.edu/nicol/ece541/slides/queueing.pdf >> >> I am not a math guy, I am a computer science guy. I need >> to >> know exactly what it is about a SQMS that makes it so >> much >> more efficient than a MQMS as shown on slide 31 of the >> above >> link. >> >> For example is it that the SQ more uniformly distributes >> the >> jobs than the MQ, thus reducing idle time? >> >> Thanks. >> > > It is because with m M/M/1 queues you will often get some > waiting in a number of queues while other servers are > idle. That does not happen with one M/M/m queue where > idle time only happens when there is no waiting. Since (in my case) these servers are providing by sharing a single computer CPU using time slicing, this would not impact my performance because an idle server would make the remaining servers run proportionally more quickly. If each server would be provided by an individual core of a quad core machine, then what you said would directly apply. Does this make sense to you? Do you see any errors in what I said? > > With real people in queues, this would lead to some of > them changing queues, which would then equalise mean > response times, though there would still be higher > variance of response times with the m queue version. > |