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Topic: Latency

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	Latency - Encyclopedia.WorldSearch (Site not responding. Last check: 2007-10-21)
		Latency measures the amount of time between the start of an action and its completion, whereas throughput is the total number of such actions in a given amount of time.
		Both latency and throughput have a dramatic effect on the design of telecommunications and computing systems, because improvements in one aspect often come at the expense of the other.
		In biology, latency also refers to the period of time between the application of a stimulus to a muscle cell and the actual contraction of the muscle.
	encyclopedia.worldsearch.com /latency.htm (629 words)

	Latency
		Latency is directly related to the spindle speed of the drive and such is influenced solely by the drive's spindle characteristics.
		For reading large continuous blocks of data, latency is a relatively minor factor because it will only happen while waiting to read the first sector of a file.
		The use of cylinder and head skewing on modern drives is intentionally designed to reduce latency considerations when switching between consecutive heads or cylinders on long sequential reads or writes.
	www.storagereview.com /map/lm.cgi/latency (538 words)

	Latency - Wikipedia, the free encyclopedia
		If an article link referred you here, you might want to go back and fix it to point directly to the intended page.
		Latency (engineering), a time delay between the moment something is initiated, and the moment its first effect begins.
		Latency (child sexuality), a psychoanalytic phase, extending from roughly age seven to twelve, during which sexuality is repressed or sublimated (now more commonly called "middle childhood" and "prepubescence").
	en.wikipedia.org /wiki/Latency (119 words)

	Which is better -- the preempt patch, or the low-latency patch? Both! (Site not responding. Last check: 2007-10-21)
		Latency is really a shorthand term for the phrase latent period, which is defined by webster.com to be "the interval between stimulus and response".
		In the context of the Linux kernel, scheduler latency is the time between a wakeup (the stimulus) signaling that an event has occurred and the kernel scheduler getting an opportunity to schedule the thread that is waiting for the wakeup to occur (the response).
		Information from Ingo Molnar is that interrupt latency for recent x86 hardware is on the order of 10µs, while interrupt handler duration is typically tens to at most low-hundreds of microseconds, and scheduling duration is a few microseconds.
	www.linuxdevices.com /articles/AT8906594941.html (5585 words)

	Improving HTTP Latency (Site not responding. Last check: 2007-10-21)
		Latency caused by client or server slowness, however, can in principle be solved simply by buying a faster computer, or faster disks, or more memory.
		For the local case, long-lived connections without pipelining reduces latency by only about 5% to 15%; this implies that the reduction in round trips is more important that the per-connection overheads.
		Note that for the relatively small transfers associated with the median image size, slow-start latencies cannot account for much of the delay; in these tests, the TCP MSS was 1460 bytes, and traces showed that slow-start did not limit the window size.
	archive.ncsa.uiuc.edu /SDG/IT94/Proceedings/DDay/mogul/HTTPLatency.html (4613 words)

	Reducing DRAM Access Latency (Site not responding. Last check: 2007-10-21)
		Latency can be lowered mainly by keeping wire lengths short and by using smaller block sizes.
		In this report, DRAM research from recent years is surveyed, the causes of latency are examined, along with techniques that have been developed to reduce latency.
		As will be demonstrated later, this constancy in latency is the result of the benefits of improved process technology being nullified by the effects of increasing chip area.
	www-cad.eecs.berkeley.edu /~jimy/classes/dram/dram_access.html (2552 words)

	GameSpot:Video Games PC PlayStation 2 GameCube PSP DS GBA PS2 PS3 Xbox 360 PlayStation 3 (Site not responding. Last check: 2007-10-21)
		Many of you reading this probably already know about latency and have taken any steps you could to decrease it, but if you're a little fuzzy on the subject or want to learn how to find out just how good (or bad) your latency is, read on.
		Simply put, latency is the time it takes for your computer to send data to a site (another computer on the Internet, either a server or a user like yourself) and for that computer's response to get back to you.
		Kali also shows you which players are closest to you in terms of latency, and if you're playing a game of Quake you can also find out the latency times between you and each person in the game by typing "ping" at the Quake console.
	www.gamespot.com /features/multiplayer/html/latency.html (806 words)

	Brooktrout White Paper: Understanding Latency in IP Telephony
		Latency is typically measured in milliseconds from the moment that the speaker utters a word until the listener actually hears the word.
		Some of the latency is incurred in the IP Telephony Gateways at either end, and the remainder is incurred by the IP network that connects the two gateways.
		Since latency is cumulative, any latency introduced by a component in an IP Telephony system will directly affect the total latency experienced by the user.
	www.telephonyworld.com /training/brooktrout/iptel_latency_wp.html (3291 words)

	Latency
		Latency is the time that the drive must wait for the correct sector to come around to where the read/write heads are waiting for it.
		Reducing latency figures greatly improves the performance of the system, particularly when dealing with access to random files on the disk.
		The use of cylinder and head skewing on modern drives is intentionally designed to reduce latency considerations when switching between consecutive heads or cylinders.
	www.pcguide.com /ref/hdd/perf/intLatency-c.html (402 words)

	Broadband satellite internet access high speed satellite internet solutions Skycasters satellite internet latency
		Latency is the amount of delay, measured in milliseconds, found in a round-trip data transmission.
		Latency is caused by several factors including the number of times the data is handled along the transmission path (by routers or servers for example).
		More importantly in the satellite world, latency is caused by the distance that the signal must travel.
	skycasters.com /satellite-internet-service-specs/system-latency.html (349 words)

	CAS Latency
		Now, after having digested all of these changes and innovations, and all the hype about "substantial speed increases", the memory manufacturers, distributors and retailers have decided to bombard us with the technical terms as to why their product is better then that of another company.
		Recently, a whole raft of resellers have been publishing comments that the CAS Latency on their Brand X modules are a huge improvement over that of Brand Y modules sold elsewhere.
		The RAS to CAS latency will be 0 (zero) cycles and the output buffers will contain the right data after the CAS latency.
	www.dewassoc.com /performance/memory/cas_latency.htm (1200 words)

	latency - a Whatis.com definition
		In some usages (for example, AT&T), latency is measured by sending a packet that is returned to the sender and the round-trip time is considered the latency.
		The latency assumption seems to be that data should be transmitted instantly between one point and another (that is, with no delay at all).
		Specific contributors to computer latency include mismatches in data speed between the microprocessor and input/output devices and inadequate data buffers.
	searchsmb.techtarget.com /sDefinition/0,,sid44_gci212456,00.html (380 words)

	Ars Technica: Understanding Bandwidth and Latency - Page 3 - (11/2002) (Site not responding. Last check: 2007-10-21)
		The average access latency of a DRAM hasn't decreased very much in the past decade relative to the average CPU speed, so this problem is not going away.
		In other words, because the initial read latency remains fixed, then as you fill more and more consecutive clock beats after the initial word the ratio of used cycles to unused cycles starts to improve.
		So if after an initial latency of 3 cycles you're able to fill the next 100 consecutive clock beats with data, without a single gap or break, then the ratio of empty cycles (three) to full cycles (one hundred) over the course of that block of 103 cycles begins to pretty good.
	arstechnica.com /paedia/b/bandwidth-latency/bandwidth-latency-3.html (999 words)

	Linux: Reducing Kernel Latency (Site not responding. Last check: 2007-10-21)
		All the latencies are still there, but the speed of swapping to disk just got reduced by many orders of magnitude.
		Then the latency is slightly higher, but it's still much lower than from a hd and you actually use less ram.
		You seem to be confusing two kinds of latency: the latency of swapping (how long an application waits before it is swapped back in) and the latency of the kernel (how long the whole system is frozen because it is swapping).
	kerneltrap.org /node/view/3810 (2081 words)

	TidBITS#367/24-Feb-97
		Latency is the same thing as seek time: the minimum time between asking for a piece of data and getting it, just like the seek time of a disk, and it's just as important.
		All that's needed is that the latency should be relatively small compared to the transmission time.
		Improving Latency -- One thing to notice is that the 38.4 Kbps serial connection between the computer and the modem, which many people don't think of as being the bottleneck, turns out to be responsible for 52 ms of the delay.
	www.tidbits.com /tb-issues/TidBITS-367.html (4355 words)

	latency from FOLDOC (Site not responding. Last check: 2007-10-21)
		The period of time that a frame is held by a network device before it is forwarded.
		Two of the most important parameters of a communications channel are its latency, which should be low, and its bandwidth, which should be high.
		Latency is particularly important for a synchronous protocol where each packet must be acknowledged before the next can be transmitted.
	wombat.doc.ic.ac.uk /foldoc/foldoc.cgi?latency (94 words)

	Navas Cable Modem/DSL Tuning Guide
		In basic terms, latency is the time needed for a round trip over the Internet between two points (e.g., your computer and remote host).
		Latency is usually not a problem with a proper TCP Receive Window (see "Why TCP Receive Window matters"), but high latency can adversely affect interactive applications such as on-line real-time gaming.
		latency (the time it takes a packet to cross the network path from one end to the other) and packet loss (where transmitted data is literally lost because of insufficient network capacity).
	cable-dsl.home.att.net (7090 words)

	Latency Tips
		Latency, in this case, is the time that a package of information takes to reach the other end of the slow link.
		For a large file, latency doesn't play much of a part; however, in the case of small packages like a DNS query, ping, or a transaction, latency can kill your performance.
		If this is compounded by name resolution and authentication latency over the slow link, the network might very well be unusable, despite the fact that the bandwidth is sufficient.
	www.netadmintools.com /art4.html (1290 words)

	It's the Latency, Stupid
		What most end-users don't know is that in the process of transferring those big files their computers have to send back and forth hundreds of little control messages, so the performance of small data packets directly affects the performance of everything else they do on the network.
		All that's needed is that the latency should not be so huge that it completely overshadows the transmission time.
		"Network latency in and of itself is not material to game playing; at least 70 to 90 percent of latency problems we see are due to the end points: the modems," he says.
	rescomp.stanford.edu /~cheshire/rants/Latency.html (5116 words)

	ClickerSolutions Training Articles -- Latency
		Saying that, let me suggest that the animal (or human, for that matter) should be given some reasonable time to receive, interpret and then respond to the command.
		If someone is trying to get Latencies less than one second, be sure that there is someone watching or a camcorder running to assure that the dog is not ANTICIPATING the cue.
		The trainer should strive for short latency between the animals response and his or her reinforcement (or other response, such as turning around or averting eyes).
	www.clickersolutions.com /articles/2002/latency.htm (487 words)

	SysOpt.com - RAM Technology Primer: CAS Latency
		Simply put, CAS Latency is a number that refers to the ratio - rounded to the next higher whole number - between column access time and the clock cycle time.
		It is derived from dividing the column access time by the clock frequency, and raising the result to the next whole number.
		Because the SDRAM specification calls for a maximum CAS Latency of 3, the worst-case scenario for overclocking to 83 Mhz.
	www.sysopt.com /tutorials/article.php/616091 (813 words)

	broadband » News » Interleaving - And Latency
		For gamers and others that are interested in minimal latency (VOIP users?), perhaps it is time to mention the following resources: BBR Qwest FAQ entry on Interleaving and this descriptive post on Interleaving.
		The source of contention with Qwest DSL is that they implement interleave on all of their ADSL lines with no option to modify it.
		The problem is that interleave adds latency to the connection, which generally is bad for games and (maybe) VOIP.
	www.broadbandreports.com /shownews/61712 (1586 words)

	Ars Technica: RAM Guide: Part II: Asynchronous and Synchronous DRAM - Page 2 - (7/2000) (Site not responding. Last check: 2007-10-21)
		There are two important types of latency ratings for DRAMs: access time and cycle time, where access time is related to the second type of delays we talked about (those internal to the read cycle) and cycle time is related to the first (those in between read cycles).
		So a DIMM with a 60ns latency takes at least 60ns to get your data to you after you've placed the row address (which is of course followed by the column address) on the pins.
		One important thing to notice in the FPM DRAM diagram is that you can't latch the column address for the next read until the data from the previous read is gone.
	arstechnica.com /paedia/r/ram_guide/ram_guide.part2-2.html (1048 words)

	Trip Wire Marketing: Tracking Behavioral Change
		I'm going to back up a second and explain in a more general sense how metrics like Latency are used, and in particular, address some of the misconceptions people have regarding customer value-based and relationship marketing techniques.
		In the cell phone case above, the measurement of Latency (number of days until customer service call) serves as the "trip wire," a raising of the hand by the customer, to say to the marketer "I'm different.
		Latency, and all the other metrics described on the Drilling Down site, are simply tools for recognizing the opportunity to take an Action in Reaction to the customer raising their hand.
	www.jimnovo.com /Behavioral-Marketing.htm (1850 words)

	CAS Latency Bulletin (Site not responding. Last check: 2007-10-21)
		As you might have guessed, there is also a RAS signal, which is shorthand for "Row Address Strobe".
		Latency refers to the time that you are waiting to get what you need.
		Then, the column address is put on the address pins, and the CAS signal is activated, to access the correct COLUMN of the memory matrix.
	www.corsairmemory.com /main/trg-cas.html (513 words)

	Web Performance Tuning, 2nd Edition: Chapter 4: Performance Monitoring
		Latency is the time between making a request and beginning to see a result.
		Some define latency as the time between making a request and the completion of the response, but this definition does not clearly distinguish the psychologically significant time spent waiting, not knowing whether a request has been accepted or understood.
		However, while latency due to traffic congestion can be reduced, increasing bandwidth will not help in cases in which the latency is imposed by routers or sheer physical distance.
	www.oreilly.com /catalog/webpt2/chapter/ch04.html (8892 words)

	Cricket config trees: latency (Site not responding. Last check: 2007-10-21)
		Now a targets file has to be created to tell cricket what you want to measure the latency of, now using your handy dandy, create a Targets file.
		Where 'foo' is the hostname of the host you want to measure latency for.
		You must be able to ping the host in order for the latency.sh script to work, as it uses ping and formats the output for cricket.
	www.dezwart.net.au /~pete/pooter/cricket/latency (289 words)

	Linux high performance low latency audio / scheduling latency tests / realtime audio. Realtime multimedia under linux ...
		low latencies are required in the multimedia field, because desktop users expect smooth aduio/video performance on their powerful boxes.
		Consider the fact that the total latency stays 99.86% of time in the +/-1ms range, which is quite good.
		Again the CPU loop latency differs maximal 0.5ms, and therefore I conclude that these long scheduling delays are a spinlocking related problem.
	www.gardena.net /benno/linux/audio (2953 words)

	Linux scheduling latency
		The timepeg framework is a base tool which is used to measure time intervals between particular points in the kernel.
		Measures scheduling latency and generates a histogram of this.
		Scheduling latency is defined here as the interval between the entry to the RTC interrupt service routine and the reading of /dev/rtc.
	www.zip.com.au /~akpm/linux/schedlat.html (946 words)

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