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  • ADSL throughput loss from Reed-Solomon encoding

    - by javano
    I'm reading about ADSL starting here and I am confused by how the Reed-Solomon encoding for ECC is limiting the available transfer rate, as much as it does (nearly half). This pdf on the same subject contains the following; A maximum of 255 sub-carriers can be used to modulate data in the downstream direction. Sub-carrier 256, the downstream Nyquist frequency, and sub-carrier 64, the downstream pilot frequency, are not available for user data, thus limiting the total number of available downstream sub-carriers to 254. Each of these 254 sub-carriers can support the modulation of 0 to 15 bits. Since the ADSL DMT data frame rate is 4000 frames per second, the maximum theoretical downstream data rate of an ADSL system is 15.24Mbps. Due to limitations in system architecture, specifically the maximum allowable Reed-Solomon codeword size (255 bytes), the maximum achievable downstream data rate is 8.16Mbps. How is this nearly halving the throughput? Is all that extra bandwidth overhead of the RS encoding? 15240000 bps (15.24Mbps) - 8160000 bps (8.12Mbps) = 7080000 bps (7.08Mbps). Where has that 7Mbps of throughput gone? EDIT: I tried to read the wiki page on Reed-Soloman but it's all crazy maths and algerbra, which I don't understand. I can understand that data is split into 255 byte codewords, because that maybe the max codeword size whilst still maintaining accuracy during transmission; But I don't understand why that means less data is sent?

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  • Reliable router with good VPN and WAN Throughput [closed]

    - by Asdande
    I have 2 cisco rv180 VPN router. These routers are giving me lots of problems. The webpages wont load correctly, slow response to load webpages plus other many issues. I have several cases pending with cisco. I give up on these routers. I would like to know if you guys can recommend me a reliable router for our 3 branches (NY - main, SC and FL). In NY- main office, we have 55 users. In SC branch, 6 users. In Florida we only have 1 (will grow soon). I need a router capable of support: 3 VPNs Site-to-Site connection VPN throughput of at least 40-50 Mbps WAN throughput at least 100 Mpbs and up PPTP Server for at least 5 PPTP users Web filtering - all users need access to internet Good Firewall Port forwarding for FTP Server - able to show the public IPs of FTP users (rv180 cannot do that, just shows me router's LAN interface IP, opened a case with cisco, now escaleted to level 2, still no answer or workaround) Dual WAN ports for balance or backup internet. Gigabit WAN/LAN ports Price between $400-$500 range. I was thinking on the TP-LINK TL-ER6120 or TL-ER6020 according to the review on smallnetbuilder.com http://www.smallnetbuilder.com/lanwan/lanwan-reviews/31983-tp-link-tl-er6020-safestream-gigabit-dual-wan-vpn-router-reviewed but I don't want to make another mistake as I did when I bought the cisco RV180. Thank you in advance,

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  • Monitoring instantaneous network throughput at one second intervals?

    - by Shaddi
    For a testing setup I have, I need to monitor the throughput through a "router"* at regular intervals of around 5 seconds or less (sub-second intervals would be very nice, but not required). Ideally, I would be able to generate a file which contained both the number of bytes and packets seen during each interval. I will eventually be generating a time-series of throughput from this data. On a previous setup using an older version of FreeBSD, there was a tool called "bpfmon" which gave me this information. However, I need to do this under a modern version of Linux (namely, Ubuntu 11.04). I have looked at both iptraf and iftop, but these do not appear to provide the resolution I need, nor do they seem to easily allow scraping the data I need. I understand iptables statistics may be able to give me what I'm after, but the examples I've seen of this seem to rely on repeatedly reading and resetting traffic counters, which seems like it could give inaccurate as read/reset is not an atomic operation. I already capture a tcpdump trace of the traffic I'm interested in on the link I want to monitor, so I am open to approaches which simply parse that. I feel like this must be a common problem though, so I am hoping there will be a standard "best practice" tool for accomplishing this. *I say "router" in quotes because I am really talking about a machine with two bridged NICs through which all the traffic I'm interested in passes.

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  • Socket throughput on localhost?

    - by gct
    I've got an app that's using sockets to push data, and I'm currently testing it on my localhost (so that the sender and receiver are on the same computer). I'm seeing between 36 and 66MB/s of throughput, which seems somewhat slow to me. What are normal throughput ranges for binary data on a local socket connection?

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  • what causes drops in apache throughput?

    - by Robbie Mckennie
    i was poking around in the windows task manager, and i found this cool network throughput graphing thing. so i wanted to see it max out, so i started downloading a 1.8gb image (from the localhost to a remote system). but, much to my surprise, it looked like this: i count 16 dips, so i divided the 1.8gb into 16 and i got 115mb. then i looked up the mtu of ip, and i knew the mtu of ethernet from my reading, both far smaller than 115mb. and since tcp is connection orientated, it doesn't have an mtu.

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  • Finding throuput of CPU and Hardrive on Solaris

    - by Jim
    How do i find the throughput of a CPU and the Hardisk on an open solaris machine. Using MPstat or iostat. I'm having a hard time identifying the throughput if it is given at all in the commands output. Eg. in mpstat there is very little explanation as to what the columns mean http://docs.sun.com/app/docs/doc/816-5166/mpstat-1m?l=en&a=view&q=syscl+mpstat I've been using the syscl column divided by time interval to find the throughput but to be honest i have no idea what a system call truelly is. I'm trying to to analyze a hardrive and CPU while writing a file to the hardisk and when at rest Thanks in advance. Jim

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  • Finding throuput of CPU and Hardrive on Solaris

    - by Jim
    How do I find the throughput of a CPU and the hard disk on an OpenSolaris machine? Using mpstat or iostat? I'm having a hard time identifying the throughput if it is given at all in the commands output. For example, in mpstat there is very little explanation as to what the columns mean. I've been using the syscl column divided by time interval to find the throughput but to be honest I have no idea what a system call truly is. I'm trying to to analyze a hardrive and CPU while writing a file to the hardisk and when at rest.

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  • Intel Wireless 4965AGN not achieving N throughput when connected to an Airport Express N network

    - by BenA
    I have an Intel Wireless WiFi Link 4965AGN adaptor in my laptop (HP Pavillion dv2000 series) which is connecting to a 5Ghz-only 802.11n network provided by an Apple Airport Express. The network is using WPA2 encryption. My desktop is also connected the Airport, via a Linksys WUSB600N USB adaptor. Both are running with the latest drivers, and the Airport is running the latest firmware. The Airport is also configured to use wide channels. The problem I have is that I never get throughput above 4MB/s when transferring files between the two machines. Even a pessimistic calculation shows a 270Mbps network as being capable of transfer rates at well above 10MB/s. I'm pretty sure I've isolated the issue to being the Intel adaptor, as wiring the desktop to the AP, and using the Linksys adaptor on the laptop immediately yielded speeds limited by the 100MB/s ethernet connection. I know that 802.11n is still a draft standard, and so mixing kit from different manufacturers can easily lead to poor results, but I was just wondering if anybody else out there has had success with this Intel adaptor on an N network? Or even better, connecting it to an Airport Express? Can anybody give me any advice on how to troubleshoot this issue? I should also mention that the Airport Express doesn't allow you to manually specify channels when running in N mode, and that I've been able to rule out interference from other Wireless LANs by scanning. There aren't any other 5GHz networks in my area. All ideas welcome! Update: A while later, I've just updated to the most recent drivers for both the Intel chip in the laptop, and the USB adaptor. Unfortunately this hasn't improved things :(. If anybody has any advice it would be be gratefully received.

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  • Load Balance WCF and Share a Remote MSMQ for High Throughput

    - by BarDev
    After a ton of reading in books and on the web, I have noticed hints of information that WCF and MSMQ can be used in achieving high throughput. The information I have seen mentions using multiple WCF services in a farm that reads from a single MSMQ queue. The problem is that I have found paragraphs here and there that mentions that high throughput can be done, but I cannot seem to find a document of how to implement it. The following is an excerpt from a MSDN article. The following paragraph is from Best Practices for Queued Communication http://msdn.microsoft.com/en-us/library/ms731093.aspx To achieve higher throughput and availability, use a farm of WCF services that read from the queue. This requires that all of these services expose the same contract on the same endpoint. The farm approach works best for applications that have high production rates of messages because it enables a number of services to all read from the same queue. This is what I'm trying to solve. I have an intranet application where a client sends a request to a WCF service. But I want the ability to load balance the WCF services on multiple servers in a farm. I also want these WCF services in the farm to do transactional reads from a remote MSMQ when an item is available in the Queue. If this is possible, an issue I have is that I do not understand the activation process of WCF to retrieve messages from a remote queue. If this is possible, does anyone know of any articles or Webcasts that would explain it in detail? BarDev

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  • How to test server throughput

    - by embwbam
    I've always used apache benchmark to try to get a rough idea of how many requests/second my server can handle. I read that it was good, and it seemed to work well. Enter node.js, which is fully event-based, so it never blocks. If I run apache benchmark on a simple hello world server it can handle 2500 requests per second or so. However, if I put a timeout in the hello world function, so that it responds after 2 seconds, apache benchmark reports a dramatically reduced throughput: about 50/s. I'm running 100 concurrent connections with ab. If I increase the concurrency, it goes up. This makes sense, because apache benchmark is basically sending out requests in batches of 100, which come back every 2 seconds. 100 requests / 2 seconds = 50 requests / second If I increase the concurrency to about 400 or 500, it starts to crash. I don't think I've hit node.js's limit, I think I'm hitting a wall in my operating system on the number of open file descriptors or sockets or something. Any way I can get a good guess about how many requests my server can handle? I want to make sure the test computer isn't the one causing the problem.

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  • 10 GigE interfaces limits single connection throughput to 1 Gb on a ProCurve 4208vl

    - by wazoox
    The setup is as follow : 3 Linux servers with Intel CX4 10 GigE controllers and an X-Serve with a Myricom 10 GigE CX4 controller are connected to a ProCurve 4208vl switch, with a myriad of other machines connected through good ol' 1000 base-T. The interfaces are actually set up as 10 Gig, according to both the switch monitoring interface and the servers (ethtool, etc). However a single connection between two 10 GigE equipped machines through the switch is limited to exactly 1Gb. If I connect two of the 10 GigE machines directly with a CX4 cable, netperf reports the link bandwidth as 9000 Mb/s. NFS achieves about 550 MB/s transfers. But when I'm using the switch, the connection tops at 950 Mb/s through netperf and 110 MB/s with NFS. When I open several connections from 3 of the machines to the 4th, I get 350 MB/s of NFS transfer speed. So each individual 10 GigE ports actually can reach much more than 1 Gb, but individual connections are strictly limited to 1 Gb. Conclusion : the 10 GigE connection through the switch behaves exactly like a trunk of 10 1 Gb connections. That doesn't make any sense to me, unless HP planned these ports only for cascading switches or strictly for many-clients-to-single-server connection. Unfortunately this is NOT the envisioned setup, we need big throughput from machine to machine. Is this a not-so-known (or carefully hidden...) limitation of this type of switch? Should I suggest seppuku to the HP representative? Does anyone have any idea on how to enable a proper behaviour ? I upgraded for an hefty price from bonded 1Gb links to 10 GigE and see exactly ZERO gain! That's absolutely unacceptable.

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  • monitoring streaming server and display throughput

    - by I__
    Scenario: laptop (running RHEL 5.3 / 5.4) with Wi-Fi allowing incoming connections (the laptop is the DHCP server and default gateway of any device that connects to it). The laptop has a streaming server installed (my app). I need to program an app that could monitor this link (device / streaming server) and display the throughput. More importantly, I need this app to be able to throttle the throughput. Think WANem but as an app, or netlimiter but (way) simpler and for RHEL. If you need clarifications, let me know. is there a library that could help me? i've done mostly windows business applications programming, and i have no clue about this stuff. please help me to get started!

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  • Low Throughput on Windows Named Pipe Over WAN

    - by MichaelB76
    I'm having problems with low performance using a Windows named pipe. The throughput drops off rapidly as the network latency increases. There is a roughly linear relationship between messages sent per second and round trip time. It seems that the client must ack each message before the server will send the next one. This leads to very poor performance, I can only send 5 (~100 byte) messages per second over a link with an RTT of 200 ms. The pipe is asynchronous, using multiple overlapped write operations (and multiple overlapped reads at the client end), but this is not improving throughput. Is it possible to send messages in parallel over a named pipe? The pipe is created using PIPE_TYPE_MESSAGE, would PIPE_READMODE_BYTE work better? Is there any other way I can improve performance? This is a deployed solution, so I can't simply replace the pipe with a socket connection (I've read that Windows named pipe aren't recommended for use over a WAN, and I'm wondering if this is why). I'd be grateful for any help with this matter.

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  • PCI max throughput

    - by allentown
    Hypothetical here, but I want to understand. Say I have a hand me down machine, 4 PCI slots, 64-bit 33 MHz PCI. How much data can that PCI bus handle? System bus is 133 MHz. I want to use one slot for a SATA II card, and the rest for Gig-E cards, building out as fast a NAS as I can. I think one slot may be AGP2x, so that leaves me 2 for Gig-E and one for SATAT II. Will I saturate, what is the max bandwidth of the PCI bus?

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  • TCP video streaming: TCP throughput(rate) and RTT

    - by misteryes
    we know that a rough estimation of TCP rate is: WINDOW/RTT, where WINDOW is the min(CWIN, RWIN), CWIN is the congestion window size of the sender, while RWIN is the receiving window. nowadays, the encoding rate of videos may be 1000KB/s(8000kbit/s), if RTT is 500ms, it needs the window size to be 2000KB. But we know that usually the receiving window size is below 64KB, there is a big gap. so if RTT is too large, TCP streaming is not possible? Is my understanding right? thanks!

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  • MRTG: Switch Port Throughput

    - by amazinghorse24
    I currently have MRTG running in a Debian box. It currently polls a Netgear Switch for the speeds of 7 or so ports and then makes the graphs of them. It currently only records the bits/sec. I would like to set up MRTG to record and display the total amount of data that has gone through the port, not just the speed of it. I am somewhat new to MIBS and SNMP and so I need some help. The switch is a Netgear GS748AT and am not quite sure where to find the MIBS for it, or which MIBS I need to accomplish my task. Any and all help is appreciated!

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  • Rejecting new HTTP requests when server reaches a certain throughput

    - by Sam
    I have a requirement to run an HTTP server that rejects new HTTP requests (with a 503, or similar) when the global transfer rate of current HTTP responses exceeds a certain level. For example, if the web server is transferring at 98Mbps, and a new HTTP request arrives, we would want to reject this (as we couldn't guarantee a good speed). I've had a look at mod_cband for Apache, limit_req for nginx, and lighttpd's rate limiting features, but none of them seem to handle my (rather contrived, granted) use case. I should add that I'm open to using pretty much any web server, and am open to implementing this in iptables rules if someone can craft such a rule! (Refusing the TCP connection is fine, it doesn't have to respond with an HTTP 503). Any suggestions?

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  • Network throughput issue (ARP-related)

    - by Joel Coel
    The small college where I work is having some very strange network issues. I'm looking for any advice or ideas here. We were fine over the summer, but the trouble began few days after students returned to campus in force for the fall term. Symptoms The main symptom is that internet access will work, but it's very slow... often to the point of timeouts. As an example, a typical result from Speedtest.net will return .4Mbps download, but allow 3 to 8 Mbps upload speed. Lesser symptoms may include severely limited performance transferring data to and from our file server, or even in some cases the inability to log in to the computer (cannot reach the domain controller). The issue crosses multiple vlans, and has effected devices on nearly every vlan we operate. The issue does not impact all machines on the network. An unaffected machine will typically see at least 11Mbps download from speedtest.net, and perhaps much more depending on larger campus traffic patterns at the time. There is one variation on the larger issue. We have one vlan where users were unable to log into nearly all of the machines at all. IT staff would log in using a local administrator account (or in some cases cached credentials), and from there a release/renew or pinging the gateway would allow the machine to work... for a while. Complicating this issue is that this vlan covers our computer labs, which use software called Deep Freeze to completely reset the hard drives after a reboot. It could just the same issue manifesting differently because of stale data on machines that have not permanently altered low-level info for weeks. We were able to solve this, however, by creating a new vlan and moving the labs over to the new vlan wholesale. Instigations Eventually we noticed that the effected machines all had recent dhcp leases. We can predict when a machine will become "slow" by watching when a dhcp lease comes up for renewal. We played with setting the lease time very short for a test vlan, but all that did was remove our ability to predict when the machine would become slow. Machines with static IPs have pretty much always worked normally. Manually releasing/renewing an address will never cause a machine to become slow. In fact, in some cases this process has fixed a machine in that state. Most of the time, though, it doesn't help. We also noticed that mobile machines like laptops are likely to become slow when they cross to new vlans. Wireless on campus is divided up into "zones", where each zone maps to a small set of buildings. Moving to a new building can place you in a zone, thereby causing you to get a new address. A machine resuming from sleep mode is also very likely to be slow. Mitigations Sometimes, but not always, clearing the arp cache on an effected machine will allow it to work normally again. As already mentioned, releasing/renewing a local machine's IP address can fix that machine, but it's not guaranteed. Pinging the default gateway can also sometimes help with a slow machine. What seems to help most to mitigate the issue is clearing the arp cache on our core layer-3 switch. This switch is used for our dhcp system as the default gateway on all vlans, and it handles inter-vlan routing. The model is a 3Com 4900SX. To try to mitigate the issue, we have the cache timeout set on the switch all the way down to the lowest possible time, but it hasn't helped. I also put together a script that runs every few minutes to automatically connect to the switch and reset the cache. Unfortunately, this does not always work, and can even cause some machines to end up in the slow state for a short time (though these seem to correct themselves after a few minutes). We currently have a scheduled job that runs every 10 minutes to force the core switch to clear it's ARP cache, but this is far from perfect or desirable. Reproduction We now have a test machine that we can force into the slow state at will. It is connected to a switch with ports set up for each of our vlans. We make the machine slow by connecting to different vlans, and after a new connection or two it will be slow. It's also worth noting in this section that this has happened before at the start of prior terms, but in the past the problem has gone away on it's own after a few days. It solved itself before we had a chance to do much diagnostic work... hence why we've allowed it to drag so long into the term this time 'round; the expectation was this would be a short-lived situation. Other Factors It's worth mentioning that we have had about half a dozen switches just outright fail over the last year. These are mainly 2003/2004-era 3Coms (mostly 4200's) that were all put in at about the same time. They should still be covered under warranty, buy HP has made getting service somewhat difficult. Mostly in power supplies that have failed, but in a couple cases we have used a power supply from a switch with a failed mainboard to bring a switch with a failed power supply back to life. We do have UPS devices on all but three of four switches now, but that was not the case when I started two and a half years ago. Severe budget constraints (we were on the Dept. of Ed's financially challenged institutions list a couple years back) have forced me to look to the likes of Netgear and TrendNet for replacements, but so far these low-end models seem to be holding their own. It's also worth mentioning that the big change on our network this summer was migrating from a single cross-campus wireless SSID to the zoned approach mentioned earlier. I don't think this is the source of the issue, as like I've said: we've seen this before. However, it's possible this is exacerbating the issue, and may be much of the reason it's been so hard to isolate. Diagnosis At first it seemed clear to us, given the timing and persistent nature of the problem, that the source of the issue was an infected (or malicious) student machine doing ARP cache poisoning. However, repeated attempts to isolate the source have failed. Those attempts include numerous wireshark packet traces, and even taking entire buildings offline for brief periods. We have not been able even to find a smoking gun bad ARP entry. My current best guess is an overloaded or failing core switch, but I'm not sure on how to test for this, and the cost of replacing it blindly is steep. Again, any ideas appreciated.

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  • Wireless range extender throughput extremely slow.

    - by Alan B
    I've got a Belkin 54G router connected to the internet, and a Belkin range extender model F5D7132. I can get the range extender connected to the parent router SSID no problem, in repeater mode as opposed to access point mode. My Windows 7 laptop connects to the extender, which has a different SSID, and it connects with the full 5 bars. The issue is that when going through the extender internet performance is murderously slow, even getting the config pages of the extender or router is bad. When I connect directly to the router, all is well.

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  • What is the fall off of subsecond throughput on Ethernet Network Interfaces

    - by Kyle Brandt
    On a network interface, speeds are given in term of data over time, in particular, they are bits per second. However, in the uber-fast world of computing -- a second is kind of a really long time. So for example, given a linear falloff. A 1 GBit per second interface would do 500MBit per half second, 250Mbit per quarter second etc. I imagine at certain units of time, this is no longer linear. Perhaps this is set by ethernet frequencies, system clock speeds, interrupt timers etc. I am sure this varies depending on the system -- but does anyone have more information or whitepapers on this? One of the main reasons I am curious is to understand output drops on interfaces. Even if the speed per second is much lower than the interface can handle -- perhaps there are spikes that cause drops for only small numbers of milliseconds. Perhaps various coalescing would hide this effect -- or perhaps increase it on the receiving interface? Do queues make a difference here? Example: So given if this is linear down to the MS we would have 1Mbit/MS, and if Wireshark isn't distorting what I see, should I see drops when I have a spike beyond 1Mbit?

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  • nginx reverse proxy slows down my throughput by half

    - by Isaac A Mosquera
    I'm currently using nginx to proxy back to gunicorn with 8 workers. I'm using an amazon extra large instance with 4 virtual cores. When I connect to gunicorn directly I get about 10K requests/sec. When I serve a static file from nginx I get about 25 requests/sec. But when I place gunicorn behind nginx on the same physical server I get about 5K requests/sec. I understand there will be some latency from nginx, but I think there might be a problem since it's a 50% drops. Anybody heard of something similar? any help would be great! Here is the relevant nginx conf: worker_processes 4; worker_rlimit_nofile 30000; events { worker_connections 5120; } http { sendfile on; tcp_nopush on; tcp_nodelay on; keepalive_timeout 65; types_hash_max_size 2048; } sites-enabled/default: upstream backend { server 127.0.0.1:8000; } server { server_name api.domain.com ; location / { proxy_pass http://backend; proxy_buffering off; } }

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  • Rejecting new HTTP requests when server reaches a certain throughput

    - by user56221
    I have a requirement to run an HTTP server that rejects new HTTP requests (with a 503, or similar) when the global transfer rate of current HTTP responses exceeds a certain level. For example, if the web server is transferring at 98Mbps, and a new HTTP request arrives, we would want to reject this (as we couldn't guarantee a good speed). I've had a look at mod_cband for Apache, limit_req for nginx, and lighttpd's rate limiting features, but none of them seem to handle my (rather contrived, granted) use case. I should add that I'm open to using pretty much any web server, and am open to implementing this in iptables rules if someone can craft such a rule! (Refusing the TCP connection is fine, it doesn't have to respond with an HTTP 503). Any suggestions?

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  • How to achieve maximum callback throughput with WCF duplex channels

    - by Schneider
    I have setup a basic WCF client/server which are communicating via Named pipes. It is a duplex contract with a callback. After the client "subscribes", a thread on the server just invokes the callback as quickly as possible. The problem is I am only getting a throughput of 1000 callbacks per second. And the payload is only an integer! I need to get closer to 10,000. Everything is essentially running with default settings. What can I look at to improve things, or should I just drop WCF for some other technology? Thanks

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  • Concise SSE and MMX instruction reference with latencies and throughput

    - by Joe
    I am trying to optimize some arithmetic by using the MMX and SSE instruction sets with inline assembly. However, I have been unable to find good references for the timings and usages of these enhanced instruction sets. Could you please help me find references that contain information about the throughput, latency, operands, and perhaps short descriptions of the instructions? So far, I have found: Intel Instruction References http://www.intel.com/Assets/PDF/manual/253666.pdf http://www.intel.com/Assets/PDF/manual/253667.pdf Intel Optimization Guide http://www.intel.com/Assets/PDF/manual/248966.pdf Timings of Integer Operations http://gmplib.org/~tege/x86-timing.pdf

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