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Visualizing System Latency

timothy posted more than 4 years ago | from the picture-says-1000-64-bit-words dept.

Graphics 68

ChelleChelle writes "Latency has a direct impact on performance — thus, in order to identify performance issues it is absolutely essential to understand latency. With the introduction of DTrace it is now possible to measure latency at arbitrary points; the problem, however, is how to visually present this data in an effective manner. Toward this end, heat maps can be a powerful tool. When I/O latency is presented as a visual heat map, some intriguing and beautiful patterns can emerge. These patterns provide insight into how a system is actually performing and what kinds of latency end-user applications experience."

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Here's the secret... (-1, Troll)

Anonymous Coward | more than 4 years ago | (#32436940)

Sperm taste is affected by what you eat, as are all secretions from the body. It is a fact that your sperms taste can be improved and making your semen taste better, can be done with a few simple diet changes. Diet has A major influence on sperm taste as it's a secretion from the body like any other. Just as your sweat can smell strongly after eating a heavily spiced meal your sperm will also reflect the spices in its taste. The make up of sperm Semen is made up of ninety percent (90%) seminal fluids including fructose (sugar) protein, and various trace minerals and nutrients. The PH of semen is 7 and scientifically neutral, yet it tastes slightly acidic. Let's take a look at the actual ingredients of semen. A man's ejaculate is actually only 1% sperm. The rest is composed of various proteins, vitamins, sugars, salts, cholesterol, and water. All the extras are what protect, feeds, fuels the sperm in its journey. As you can see in terms of semen's composition, it's fairly obvious that what you eat will make it taste better or worse! Getting a sweeter taste With sperm taste, the aim is to make it taste sweeter. All men have a semen taste that is exclusive to them, but the major complaint on sperm taste is normally always the same: It tastes bitter or salty; let's look at how to make semen taste sweeter 10 Tips for better semen taste Here then are 10 simple do's and don'ts to improve the taste of your sperm and make your semen taste better and sweeter: 1. Cut out alcohol, caffeine, recreational drugs and nicotine- they're all pollutants. 2. Drink lots of water 1 - 2 liters a day to flush out body toxins. 3. Fruit get plenty each day and sweeten your sperm taste Pineapple, papaya cranberry, melons, mangos, apples grapes are all good choices. These fruits are high in natural sugars and offset the bitter taste. 4. Eat plenty of vegetables which are generally good for improving sperm taste. 5. While it is true vegetarians generally have better tasting sperm there are vegetables to avoid: Any vegetables from the cabbage family big offenders also include Cauliflower, broccoli, or asparagus: 5. Cut red meat consumption this is one pf the main offenders when it comes to making sperm taste salty. Dairy produce such as milk and cheese also make sperm taste salty. Make sure when you eat protein you get good quality lean protein such as chicken and turkey. Fish is claimed by some to be an offender in terms of taste, but this seems to vary between individuals. Try it and see the affects before cutting it out, fish is a major part of a healthy diet, so don't cut it out! 6. Avoid heavy spices such as Garlic and onions, they're big offenders when it comes to sperm taste, as they have a high sulfur content. 7. Do not buy products that claim to make your semen taste better there is no evidence that they work. Your semen can be made to taste better by overall changes in diet and lifestyle, it's a complex formula and a good healthy diet has the biggest affect. 8. Parsley, wheatgrass, and celery are particularly recommended for sweeter semen taste, because of their high chlorophyll content. 9. Cinnamon, cardamom, peppermint and lemon are particularly recommended for making semen taste sweeter. 10. Avoid junk food, they're loaded with chemicals and preservatives that pollute your body and your semen's taste. Try and eat food "from the earth" i.e. as naturally as possible. Also consider taking a zinc and selenium supplement, both are needed for healthy sperm and can make the taste better. Finally, strong smelling semen may indicate an infection, so if your semen taste doesn't change when you change your diet, you should consider a visit to the doctor. Your aim with your diet is to eat one that helps your overall health and the above recommendations will not only make your semen taste better you will also feel fitter and healthier as well. Keep in mind that you can eat some of the foods we don't recommend for sperm taste. You can enjoy red meat and the occasional spiced curry just keep in mind the following when considering sperm taste: What you put into your body takes between 12 and 24 hours to secrete out and you should simply keep this in mind before eating and deciding whether you want a better sperm taste on that particular day or not! For more sensible advice on sperm taste and making your semen taste better, as well as male fertility, general health and sex advice including: Articles ezines, magazines and downloads visit: http://www.net-planet.org/sexhealth.html [net-planet.org]

Re:Here's the secret... (-1, Troll)

Anonymous Coward | more than 4 years ago | (#32437180)

Gay! Gay! You are a fucking gay!

Re:Here's the secret... (1)

X0563511 (793323) | more than 4 years ago | (#32438144)

Or female. What's your point?

Re:Here's the secret... (0)

Anonymous Coward | more than 4 years ago | (#32437374)

Do you have any advice on how i can improve the taste of the santorum i felch from my boyfriend's ass after i jizz in it?

another solution to an already solved problem... (2, Insightful)

Michael Kristopeit (1751814) | more than 4 years ago | (#32436986)

mapping latency in a system using colored maps representing throughput has been a tool of db and network sysadmins for many many MANY years.

Re:another solution to an already solved problem.. (1, Informative)

Anonymous Coward | more than 4 years ago | (#32437186)

How bout you RTFA before you make you're smartass comments, since yours is almost a direct fucking quote from it. However, this isn't about measuring network latency, it's about disk latency, something that until recently was extraordinarily hard to measure.

Re:another solution to an already solved problem.. (1)

Jorl17 (1716772) | more than 4 years ago | (#32437262)

You're = your in this case. Other than that, nice comment.

Re:another solution to an already solved problem.. (1)

Michael Kristopeit (1751814) | more than 4 years ago | (#32437300)

how bout i did read the fucking article? how about i never said it was about network latency? how about measuring disk latency is no different than measuring ANY latency? how about db latency using optimized table handlers ends up becoming exactly a problem of disk latency?

Chill man. (0)

Anonymous Coward | more than 4 years ago | (#32438112)

Woah, Michael. It's OK. It's just slashdot.

Just kick back with a couple of these Ancient-New-World-Beers [slashdot.org] and chill out man...

Know why you got that 0 next to your name? I could mod you down to oblivion but I think my beer comment is funnier. What's better is since I'm AC I still can.

Re:Chill man. (1)

Michael Kristopeit (1751814) | more than 4 years ago | (#32438442)

woah, yourself. you are NOTHING.

Re:Chill man. (0)

Anonymous Coward | more than 4 years ago | (#32438486)

Anger issues anyone?

Re:Chill man. (1)

Michael Kristopeit (1751814) | more than 4 years ago | (#32438542)

ignorancy issues, anyone?

first you replace "your" with "you're".... it takes a special kind of moron to do that.... then you claim measuring disk latency is something that is in some way more difficult or different than measuring any other kind of latency.

you are doing a service to yourself posting as AC to hide your identity... until that changes, you are NOTHING.

Re:Chill man. (0)

Anonymous Coward | more than 4 years ago | (#32439716)

I'm not pretending to be anybody else. I'm not the original AC that disagreed with you, and honestly I know nothing about latency, but nice attitude. I'm sure it serves you well in the real world...

Re:Chill man. (0)

Anonymous Coward | more than 4 years ago | (#32440214)

ur mums face serves me well in the real world.

disagreeing with someone that claims i'm wrong with statements undeniably false absolutely serves me well... EVERYWHERE.

Re:Chill man. (0)

Anonymous Coward | more than 4 years ago | (#32440026)

ignorancy issues, anyone?

HAHA ignorancy. I missed that first read.

Re:Chill man. (0)

Anonymous Coward | more than 4 years ago | (#32440422)

did you miss it because you're lazy or because you're ignorant?

Re:another solution to an already solved problem.. (1)

Xeleema (453073) | more than 4 years ago | (#32441428)

Crimey! Slashdot needs a "Hide all comments from UIDs >1M"

Re:another solution to an already solved problem.. (1)

Michael Kristopeit (1751814) | more than 4 years ago | (#32441624)

i agree that your children will probably be idiots not worth listening to...

Re:another solution to an already solved problem.. (0)

Anonymous Coward | more than 4 years ago | (#32445454)

You're an interesting man, Michael. How's Rachel ? And the dogs ? I do hope they don't suffer from your anger issues. You might want to consider not putting quite as much about yourself on the internet, if you're gonna be doing the rabies thing at people; although I'd suggest a better alternative would be to get rabies shots.

Re:another solution to an already solved problem.. (1)

Michael Kristopeit (1751814) | more than 4 years ago | (#32446930)

i made a statement of fact. you claimed i didn't read the article. you called me a smartass. you made claims about measuring disk latency that could not be more wrong. but most of all you said i was wrong.

then i call you out on it USING THE SAME PHRASING YOU USED, and then you attack that... YOU WERE WRONG. you are probably wrong more than you are right, which has helped you develop this accusatory defense mechanism. i do have a wife. i do have dogs. you might want to consider putting a little more about yourself on the internet... perhaps then someone could find you and educate you, monkey.

you are NOTHING.

Re:another solution to an already solved problem.. (0)

Anonymous Coward | more than 4 years ago | (#32448400)

Hmm. It appears you have a hard time grasping the concept of "Anonymous Coward".

"Anonymous Coward", dear smartest pencil, isn't an actual person. It's just another name for an anonymous poster. I'm not the Anonymous Coward you first exploded at, nor are either of us the one you exploded at second, and so on.

I happen to be the one you just replied to, but that's just because you amuse me and I'm actually bothering to track that post for a few days.

A lot of us may be NOTHING, but I guess that makes us mostly the same as what you've got behind the eyes, monkey. Have an education that doesn't involve wether single quotes are more efficient than double quotes in PHP.

Re:another solution to an already solved problem.. (0)

Anonymous Coward | more than 4 years ago | (#32448626)

so your point is, anonymous posters should be ignored... and yet you yourself still post anonymously.

you can't buy that kind of stupid.

Re:another solution to an already solved problem.. (0)

Anonymous Coward | more than 4 years ago | (#32459510)

Neh. My point was that Mr Kristopeit apparently didn't grasp that there was a difference between us Anonymous Cowards, and I suspect that an overdose of AC comments at him might be the cause of his outbursts.

He's stopped replying, too, so I guess he got it. Well, either that or he had a heart attack from all the excitement.

Re:another solution to an already solved problem.. (1)

Michael Kristopeit (1751814) | more than 4 years ago | (#32461248)

how about you read my comment IN THIS THREAD, POSTED BEFORE YOURS [slashdot.org] that includes me clearly explaining the concept of Anonymous Cowards, and proving my understanding.

then you sweep in like a donkey with claims that that didn't just happen...

you are the worst kind of stupid.

if i respond to an AC, and an AC responds back, i will assume it was the original AC until told otherwise. the burden of proof is not on my shoulders... i've already proven i'm the same person. you can't prove you aren't the same AC.

you are NOTHING.

Re:another solution to an already solved problem.. (0)

Anonymous Coward | more than 4 years ago | (#32474524)

And here I was, about to delete my bookmark to this. You truly are an endless source of amusement.

There's thousands, potentially millions of ACs, and you assume that the same guy that launches a one-off comment will keep coming back to every comment he makes to see if you've answered? Dude, the only reason I've bookmarked this is that your incredibly arrogant attitude provides me a measure of amusement. I really couldn't be bothered to bookmark and check every anonymous comment I make.

You appear to severely overestimate your own importance. Carry on entertaining me, minion.

Re:another solution to an already solved problem.. (1)

Michael Kristopeit (1751814) | more than 4 years ago | (#32485778)

i have never once said i was important.

you are NOTHING.

Re:another solution to an already solved problem.. (1)

vegiVamp (518171) | more than 4 years ago | (#32494276)

One small sentence and your key signature ? How disappointing. I guess your batteries are running down, by now - too much screaming will make you hoarse.

Shame, I'll have to find another source of amusement now.

Re:another solution to an already solved problem.. (0)

Anonymous Coward | more than 4 years ago | (#32498350)

ur mums face works for me

Re:another solution to an already solved problem.. (1)

azrider (918631) | more than 4 years ago | (#32444228)

How about "Hide all comments where $UID > $MINE " ?

Re:another solution to an already solved problem.. (1)

Macka (9388) | more than 4 years ago | (#32451290)

That wouldn't leave me with very many people to talk to ;)

Re:another solution to an already solved problem.. (0)

Anonymous Coward | more than 4 years ago | (#32437432)

However, this isn't about measuring network latency, it's about disk latency, something that until recently was extraordinarily hard to measure.

Not on my planet. Those who forget history are doomed to repeat it. I've been making my living doing mostly performance work for fifteen years, including the production of countless graphs, animations, 3d visualizations, and other visual (and sonic) aids of metrics such as disk latency. And I'm not talking mrtg, and other crude views. Measuring the past is one thing, but predicting the future is much more interesting.

Disk latency is just a tiny part of a much larger picture. The author of TFA is doing good work, and I fully support his writing about it, developing tools, etc. But it is nothing new and should not be represented as such. Except the bit about yelling at disk drives. That's very cool. That dude needs to be recognized for his uncanny ability to yell, and intimidate hardware. I would support funding further research into whether extreme profanity is of any additional benefit. That's an open source project I would get involved in!

Re:another solution to an already solved problem.. (1)

Colin Smith (2679) | more than 4 years ago | (#32438308)

something that until recently was extraordinarily hard to measure.

Really?

Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await svctm %util
hda 0.00 0.00 114.85 0.00 0.45 0.00 8.00 0.73 6.28 6.34 72.87

Where await and svctm are average wait (milliseconds) for the disk & queue and service time for the disk.

Or do you mean something else?

 

Re:another solution to an already solved problem.. (2, Insightful)

forkazoo (138186) | more than 4 years ago | (#32439424)

Really?

Device: rrqm/s wrqm/s r/s w/s rMB/s wMB/s avgrq-sz avgqu-sz await svctm %util
hda 0.00 0.00 114.85 0.00 0.45 0.00 8.00 0.73 6.28 6.34 72.87

Where await and svctm are average wait (milliseconds) for the disk & queue and service time for the disk.

Or do you mean something else?

The data presented in the article are actually quite a bit more subtle and interesting than the summary data you've got there. It's probably be impossible to notice the effects of the "icy lake" phenomenon they describe with average summary data like that, or to appreciate the effect of shouting. (Most IO's happen relatively quickly during the shouting, so the average doesn't skew up very high. What's remarkable about the shouting is the sudden burst of outliers indicating a few accesses with terrible performance.)

Re:another solution to an already solved problem.. (1)

Xeleema (453073) | more than 4 years ago | (#32441444)

the summary data you've got there

Funny. I recall the command syntax for that one lets you setup intervals per second. That would be the "black foot" that gets you out of the "icy lake" phenomenon you describe.

wow, standards have fallen? (0)

Anonymous Coward | more than 4 years ago | (#32437012)

I hope beutiful isn't commonplace...
New management?

Re:wow, standards have fallen? (0)

Anonymous Coward | more than 4 years ago | (#32437250)

New management?

What? No. You must be new here.

Pyke (-1, Troll)

headkase (533448) | more than 4 years ago | (#32437044)

Shameless plug for writing optimized programs: Pyke [sourceforge.net] . I'm tentatively learning this framework: myself [networkedblogs.com] .

Relevance to Latency (0, Offtopic)

headkase (533448) | more than 4 years ago | (#32437286)

Sorry, should have mentioned why this comment should be in this story. The flip side of measurement of your systems latency to improve performance is to optimize your program as well as the system. Pyke is a meta-programming framework and in effect caches your programs structure and variables dramatically improving performance. Which is latency.

So shouting is bad (1)

0racle (667029) | more than 4 years ago | (#32437242)

I guess shouting at systems to make them start working has the opposite effect. Who knew a server was so emotional.

Re:So shouting is bad (1)

gazuga (128955) | more than 4 years ago | (#32437734)

Correct - see here [youtube.com]

The sky is falling... (4, Funny)

PPalmgren (1009823) | more than 4 years ago | (#32437332)

Informative article, all on one page, not chock full of ads. Now excuse me while I stock my bunker.

Re:The sky is falling... (2, Informative)

aicrules (819392) | more than 4 years ago | (#32437356)

All truly informative articles follow this paradigm. You only need the multi-page, multi-ad to pay for content that very few people will read because it's not that informative or interesting.

Re:The sky is falling... (0)

Anonymous Coward | more than 4 years ago | (#32437652)

That's because it's a direct link to a professional organization that is hosting the primary research ... not a journalistic website. Professonal orgs make most of their money from member dues and donations, and as such have no need for ads.

The fact that it also happens to be an incredibly good article helps as well, obviously.

At Queue, the sky is always falling... (1)

davecb (6526) | more than 4 years ago | (#32438778)

I really like ACM Queue, which regularly prints articles for practitioners about things which both we and our more academic colleagues care.

I recommend it, and on rare occasions, contribute [slashdot.org] .

--dave

pretty graphs (-1, Troll)

gumbi west (610122) | more than 4 years ago | (#32437362)

Did anyone else notice that the article has no actual information in it? Also, the graphs are impenetrable until you have read tons of text (bad sign!).

Also, "Some of the heat maps, such as the rainbow pterodactyl, are also interesting examples of how deep and beautiful a simple visualization can be." translation: "I like pretty graphs and have found they can substitute for actual information."

Re:pretty graphs (5, Insightful)

ushering05401 (1086795) | more than 4 years ago | (#32437968)

These visualizations are used to condense the information gathered on one second intervals from running systems. Any graph of substantially advanced material is going to require explanation until you understand what is being measured, how it is being graphed, and how this information translates in real world performance.

Of course a casual reader from the net needs to read text to understand what is going on. These aren't sales figure pie-charts and shouldn't necessarily be accessible for uninformed parties.

On another note.. Do you think casual readers would have any more success interpreting the raw data files? Anyhow, I am interested in the technique as it is not one I am currently using. With a little practice this may be a good at a glance technique.

Re:pretty graphs (1)

gumbi west (610122) | more than 4 years ago | (#32439840)

Do you actually think the concept of a heat map is new?

A great graph has, (1) a title, (2) labeled x- and y-axes, (3) a 3D figure should also have labels for intensity and the z-axis. All text should be readable or removed. Generally, difficult to interpret figures should have a paragraph below them explaining (a) what they show and--ideally--(b) what the researcher concludes form the graph when this is not obvious.

Re:pretty graphs (1)

jgrahn (181062) | more than 4 years ago | (#32449150)

On another note.. Do you think casual readers would have any more success interpreting the raw data files? Anyhow, I am interested in the technique as it is not one I am currently using. With a little practice this may be a good at a glance technique.

Yes -- I do things like these all the time, and I frequently have reason to go: "Oh, our systems behave like *this* in reality?" I wrote an article on the subject (with gnuplot as the visualization tool): http://snipabacken.se/~grahn/gnuplot_kicks_ass/ [snipabacken.se]

Re:pretty graphs (1, Insightful)

Anonymous Coward | more than 4 years ago | (#32437978)

The article presented plenty of information related to it's topic. The topic was that using a heat map to describe latency is more useful than simple averages and maximums displayed as line graphs. The article then analyzed certain interesting cases were a heat map had information that would not have existed in a line graph. What you are griping about is that the topic itself is simple and that the article is full of individual analyses that provide support for the topic.

Re:pretty graphs (1)

gumbi west (610122) | more than 4 years ago | (#32439846)

But almost all there concluding remarks on a figure are, "we don't understand this graph"

Re:pretty graphs (2, Insightful)

azmodean+1 (1328653) | more than 4 years ago | (#32445216)

That's the point, a good engineer's (or scientist's) response to new data that they can't fully explain is generally unmitigated glee, it means they've found something new. My takeaway from the article is, "try this new technique/tool, you'll see new data".

On another note, I've done some very basic analysis of disk performance at work, and this approach would have allowed me to be much more confident in my results. As it was, basically all I could do when comparing disks and filesystems was use iozone to characterize the "knee points" the article keeps mentioning, and try to map changes in aggregate numbers to saturation of various interfaces and/or devices. This method for actually getting sampling data for latency, and potentially from real workloads even, would have been extremely helpful.

Re:pretty graphs (1)

gumbi west (610122) | more than 4 years ago | (#32445638)

uh, "a good engineer's (or scientist's) response to new data that they can't fully explain is generally unmitigated glee, it means they've found something new." perhaps, but generally you don't ask others to read about it until you understand something about the phenomenon OR it has withstood several attempts to understand it.

You also wrote, "new technique" but what is new? Do you think they invented the heat map, or exploratory data analysis?

Re:pretty graphs (1)

Gothmolly (148874) | more than 4 years ago | (#32438064)

ACM is a scholarly, research-oriented group. If you're looking for spoon-fed, PCMagazine types of charts and graphs, look elsewhere. Lots of text generally means that someone with brains has to interpret the data, because the interpretation is non-trivial.

old school visualization (5, Interesting)

bzdang (819783) | more than 4 years ago | (#32437684)

Back in the day, working at an instrumentation company as a mechanical guy, I stopped to watch the senior electronic design engineer who was doing something that looked interesting. He had an old persistence-type storage oscilloscope hooked up to the rack-mount computer for a new instrument system and was watching the scope display, which was producing some fascinating patterns. Knowing f'all about this stuff but intrigued, I asked him to explain what was happening. He explained (and I'll butcher the explanation with layman's terms) that he was using d/a converters on the high and low bytes of the program address? to drive the x and y axes of the scope, and watching to see where, in the software, that the processor was spending much of it's time. He pointed to a hot spot on the scope display and said that this was where he would concentrate on optimizing his code. Fwiw, I thought that was pretty cool.

Re:old school visualization (1)

harrkev (623093) | more than 4 years ago | (#32437736)

This must have been a long time ago, back when you had easy access to the address lines.

Now, that same job would be VERY difficult! Most data accesses occur to data in the cache, which is not brought out to pins outside of the processor. And when memory accesses do happen, they happen over dedicated DDR address lines, which are very high speed (hard to probe), and the address lines are used to access both rows and columns, so some external circuitry is needed in order to determine what the real address is.

Cool idea though, but pretty hard to pull off these days without a serious engineering effort.

Sure, but it'd work quite well (0)

Anonymous Coward | more than 4 years ago | (#32438358)

in a simple microcontroller setup

Re:Sure, but it'd work quite well (0)

Anonymous Coward | more than 4 years ago | (#32438498)

You have not tried to snoop the address bus of the program memory on a simple microcontroller in the recent 20 years have you? Most microcontrollers today are basically "computers on a chip", internal flash to run program from, internal sram for data, internal eeprom for storing settings, internal peripherals for output.

Re:Sure, but it'd work quite well (1)

jnork (1307843) | more than 4 years ago | (#32441724)

As a compromise, consider capturing the return address in a timer interrupt and stuffing into a DAC or two. Of course that requires that you have an unused DAC (or two) on board, a timer, and processing time available in the interrupt, and the result probably won't be as smooth as the DAC directly on the bus. Still, if you can do it it's better than nothing.

If you can't, perhaps you can use a different peripheral and some external logic. SPI to a shift register, perhaps? Or I can see having a second processor and sending it serially, then the second processor outputs the DAC.

Anyway, I can see using variations of this technique on some of my projects. Pretty cool idea, really.

Re:old school visualization (0, Troll)

pipatron (966506) | more than 4 years ago | (#32438534)

OMG! Thanks for telling us this, I bet no one that knows what a computer program is knew this!

Re:old school visualization (1)

tuomoks (246421) | more than 4 years ago | (#32454110)

Yep, probably very long time ago, not that it was easy even in mainframes but very useful, no overhead to measure, as you maybe know - a mainframe is happy when 101% busy - the measurement overhead is very often a bad thing! It was fun, really, but reading the results wasn't always easy - is anything? Later on 80's / 90's simulating, estimating, measuring, etc file / disk / network systems the heat maps created with our hardware people on channels, controllers, disks, caches, DMA, etc timings / sizes / rates were indispensable - accurate within microsecond (memory nanoseconds) / no overhead / all the measure points you can dream. Common in all large software / system development - I wonder how it is done today, how many could use these devices / read the results correctly? Sometimes just wondering - have we lost some skills over years? Actually same heat maps can be used in networks very well - very useful! In wireless (and wireline but wireless usually has much more variations) networks you can see the latency, other problems and the performance easily with one look on a nice "heat map", maybe displayed on a 42" screen today.

Re:old school visualization (1)

snowboardin159 (1744212) | more than 4 years ago | (#32437796)

sounds like a good strategy, and much like what TFA is doing. Id be interested to see something like this IRL, or streaming, or in graphs that were readable.

Re:old school visualization (0)

Anonymous Coward | more than 4 years ago | (#32441768)

Old, old, old school.
But very cool.

I once put the stack pointer to an area of memory mapped to the video buffer.

Game Theory and other modeling (1)

masterwit (1800118) | more than 4 years ago | (#32438000)

After reading the article, this idea of a "heat map" or frequency distribution mapping (of sorts) can (sort of) be summed in:

A particular advantage of heat-map visualization is the ability to see outliers.

I find this particularly interesting as this graphically now allows a way to "filter" the real outlier out from a sea of data. Also,

Instead of a random distribution, latency is grouped together at various levels that rise and fall over time, producing lines in a pattern that became known as the icy lake. This was unexpected, especially considering the simplicity of the workload.

And concluding the section on what they dub as the "icy lake"...

To summarize what we know about the icy lake: lines come from single disks, and disk pairs cause increasing and decreasing latency. The actual reason for the latency difference over time that seeds this pattern has not been pinpointed; what causes the rate of increase/decrease to change (change in slope seen in figure 5) is also unknown; and, the higher latency line seen in the single-disk pool (figure 4) is also not yet understood. Visualizing latency in this way clearly poses more questions than it provides answers.

Without actually seeing the data or knowing the specifics of latency, from a pure mathematical standpoint I wonder what would result if one treated the set of numbers (from each disk) as a random sequence, identifying outliers (as they did using this heat model)...then graphically mapping those using a "chaos game theory algorithm". By using a graph to statistically analyze/visualize the "outliers", perhaps more could be revealed on the "randomness" of how one disk or a pair of disks reacts relating to the whole system.

I do not claim to know much in this area at all and this is merely speculation on how the set of numbers "randomness" may be approached...

Sun (0)

Anonymous Coward | more than 4 years ago | (#32438012)

Of course nobody credits Sun for Dtrace in the article...ugh

DTrace is amazing, but... (1)

lostsoulz (1631651) | more than 4 years ago | (#32438180)

...it's a shame that instrumentation of things such as EMC's PowerPath are a little painful. I guess there will always be gaps where vendor meets vendor and closed source meets open source, but it remains rather complex to analyse what's happening in Solaris with PowerPath and some Storage Foundation stirred in for good measure. Impossible? No...but maybe we'd all benefit from a little more interoperabilty?

It's a great article though - Brendan's a DTrace authority is impressive.

Effective? (0)

Anonymous Coward | more than 4 years ago | (#32439050)

Summary of the article: The graphs are pretty cool, but we do not understand what they tell us.

Thats not quite what I would call effective...

easy. (2, Funny)

jd2112 (1535857) | more than 4 years ago | (#32439634)

Take, for example, AT&T Network performance:
Current: Snail
Expected, after customers leave in droves over data plan changes: Snail on meth (see yesterday /. article)
Expected, once AT&T upgrades equipment: Sloth on vallium

Heat? (2, Funny)

scottwilkins (1224922) | more than 4 years ago | (#32439810)

Heat kinda makes me slow too...
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