This is one of the reasons I prefer to use Linux over systems such as Windows or OSX. I love the public discussion over the direction of technical details; the to-and-fro on the benefits of esoteric technologies.
The whole openness of the culture.
The whole openness of the culture.
The net result of that is a generally acknowledged fact that Windows is slower than Linux when running complex workloads that push network/disk/cpu scheduling to its limit: https://news.ycombinator.com/item?id=3368771 A really concrete and technical example is the network throughput in Windows Vista which is degraded when playing audio! http://blogs.technet.com/b/markrussinovich/archive/2007/08/2...
Note: my post may sound I am freely bashing Windows, but I am not. This is the cold hard truth. Countless of multi-platform developers will attest to this, me included. I can't even remember the number of times I have written a multi-platform program in C or Java that always runs slower on Windows than on Linux, across dozens of different versions of Windows and Linux. The last time I troubleshooted a Windows performance issue, I found out it was the MFT of an NTFS filesystem was being fragmented; this to say I am generally regarded as the one guy in the company who can troubleshoot any issue, yet I acknowledge I can almost never get Windows to perform as good as, or better than Linux, when there is a performance discrepancy in the first place.
One could argue a better decision would've been to pick Core 2 and/or 3, but there's nothing to guide the scheduler to make this decision.
But it's not that "DPCs" are a design flaw. It's the way that Windows drivers have been encouraged by Microsoft to be written. You'll see most Windows drivers have an ISR and DPC. If you look at IOKit (Mac's driver framework), almost all drivers run at the equivalent of Passive Level (IRQL 0) outside of the ISR/DPC path -- the OS makes sure of that.
Because Windows driver devs are encouraged to write ISR/DPC code, and because this code runs at high IRQL, it means that bugs and inefficiencies in drivers show a much larger performance degradation. And when you buy a shit 0.01$ OEM NIC, and you have to do MAC filtering, L2 layering, checksum validation and packet reconstruction in your DPC, plus there's no MSI and/or interrupt coalescing, you're kind of f*cked as a Windows driver.
Also w.r.t to your other point, Threaded DPCs do exist (since vista) which run at PASSIVE_LEVEL.
As for Threaded DPCs, not only does nobody use them in real life, but they MAY run at PASSIVE. The system still reserves the right to run them at DPC level.
Really the only way out of the mess is Passive Level Interrupts in Win8... Which likely nobody outside of ARM ecosystem partners will use.
Though, as a user of badly written drivers, I'm totally fucked. Its too bad the OS design does not allow for the user control any aspect of this (well apart from MaximumDpcQueueDepth).
- Typical driver dev: Knows nothing about DPC Importance Levels, and sticks with medium (default): IPIs are not sent to idle cores, so device experiences huge latencies as the DPC targeted to core 7 never, ever, gets delivered.
- Typical driver dev 2: Hears about this problem and learns that High/MediumHigh Importance DPCs cause an IPI to be delivered even to idle cores: wakes up every core in your system round-robin as part of his attempt to spread/reduce latencies, killing your battery life and causing IPI pollution.
Now I hear you saying: "But Alex, why not always target the DPC only to non-idle cores?". Yeah, if only the scheduler have you that kind of information in any sort of reliable way.
Really this is clearly the job of the OS. As it stands now, targeting DPCs on your own is a "fcked if you do, fcked if you don't" proposition.
You do get a few more variables you can play with as a user, but changing them will usually lead to worst problems than it would solve. Many drivers take dependencies on the default settings :/
Honestly.. I've spent countless hours hunting down bad drivers to fix audio stutter and other crap on my gaming PC. I've finally got DPC latency under 10microSec and I'm not touching a thing :)
It was just a simple example of something that could change for the better in terms of performance, but that probably won't because it's a significant amount of code churn with little $$$ benefit.
I was honestly surprised that a core-balancing algorithm was added in Windows 7, but that was done at the last second (RC2) and by a very senior (while young) dev that had a lot of balls and respect. Sadly he was thanked by being promoted into management, as is usual with Microsoft.
http://technet.microsoft.com/en-us/video/windows-7-and-windo...
http://download.microsoft.com/download/8/C/2/8C21BAFE-3432-4...
Changes in Windows 8 were smaller, but it did for example improve the efficiency of memory allocation:
http://blogs.msdn.com/b/b8/archive/2011/10/07/reducing-runti...
Windows 7 and 8 both have lower system requirements than Vista while offering more features. That fact was widely advertised and acknowledged. Sure, not everything was improved, but it's not true that MS never fixes things for better performance. They simply have different business priorities, such as supporting tablets in Windows 8 rather than supporting 1000 Mbps.
Take a look at these benchmarks that were posted here recently: https://news.ycombinator.com/item?id=5644880
There isn't a single comment in that whole thread about how outrageously bad EC2 performance is. Meanwhile I'd bet that most HN startups run on EC2, heroku or other virtualized cloud platforms. And how many are using dog slow interpreted languages like python or ruby? It looks to me like people around here are quite willing to take very large performance hits for the sake of convenience.
I find Windows to be a small performance hit for the sake of convenience.
I used to use Windows exclusively until about 4 years ago. Up to the time i switched, I occasionally was testing a few Linux distros, and repeatedly came to the conclusion that drivers were still an issue, and that Linux wasn't ready for the average user's desktop.
Not so anymore, since about 2009. From that time on, the only thing without a Linux driver I encountered (there are many more, just not that widespread that it should matter) was an HP printer. Which is why I stopped using Windows altogether.
My experience since then? Windows is a royal PITA to use and maintain. Linux, with KDE as the desktop manager, isn't just faster, it's way friendlier for users. One example, which to me is huge: on Windows, you need to run the updater of every f..ing software provider from which you have purchased an app. On Linux, there's just one updater for everything. another one: on Windows, even with all the discount programs for students and others, you have to spend thousands of dollars before you get equivalents of all apps installed that you get for free when you select developer workstation for a Linux installer.
Agreed, games are the only thing that Linux doesn't yet cover as well as Windows - both development and play. However, wanna bet that Linux will tip the balance in this area too, in at most five years?
The links that you posted in support of your claim are irrelevant IMO.
Compiling has nothing whatsoever to do with windows internals. You're comparing Visual Studio a full fledged IDE with dozens of extra threads running source indexing, source code completion/help indexing and dozens of other things that gcc does not do. To make a fair comparison you will have to just compare cl.exe with gcc with a bunch of makefiles (yes you can have makefiles on windows too).
Then your "real concrete and technical" example is actually a bug in windows vista which was fixed around 6 years ago.
And your claim about MFT fragmentation kind of sounds bizzare to be honest. Since Vista the OS internally runs a scheduled task to run a partial-defrag that takes care of it. I'm not sure what went wrong in your case.
I'm not saying you imagined the slowness, I believe you experienced what you said. So lets test your theory. Since you can write code runs slower only on Windows - give us some C code that runs horribly on Windows.
What you did is try to move the goal posts.
I guess the only solution is to tag my comments "Hey this is a casual conversational comment" or else people read too much into the wording.