i5 Extracting and WinRar

ProtoType · Dec 29, 2012

Hello, I guess I'm sort of a newbie when it comes to the whole quad core processor thing that i5's and i7's have.

When extracting files with WinRar, one file will go quickly, but when I extract two at the same time, it slows down.

I thought the whole thing with i5 was to be able to run two things at the same time at same speeds?

Why does the extracting slow down on both?

Am I not understanding how the quad processors work?

Thanks in Advance!

fireberd · Dec 30, 2012

Some of the multi-processor (personally) is myth. However doing two things at the same time with the same program (e.g. unzipping files) can potentially be a problem.

Multi-tasking (doing more than one thing at a time) is standard basic PC operation, whether its a single core processor or multi-core. Most processor threads (cores) are controlled by the OS, however an application can also take advantage of multi-cores if it is designed for that. For example, I use Sonar recording studio software. The older versions only left the core selection and processing to the OS, the latest version takes advantage of the multi-core capabilites and does some selection within the program.

But to answer your question, I don't see any difference on most programs between the old Q6600 CPU system I had and the new systems I have - one with an i7 3770 and the other with an i5 3550. They do basically load and process a little faster as I have SSD drives, but many programs - to the naked eye - are not any different. The only program that visibly works better with the new multi-core CPU's is the Sonar program I referenced. There is also the built in OS controlled "Core Parking" that will "park" some cores depending on what is happening (there is a way to disable core parking).

startas · Dec 30, 2012

ProtoType said:
I thought the whole thing with i5 was to be able to run two things at the same time at same speeds?

You couldn't be more wrong ... THE IDEA of multi-core processor is to run as many things as fast as possible as the same time.

Why does the extracting slow down on both?

Because, first extraction already uses as many cores as possible, i.e. 4. then you start extracting other file, so it gets 2 cores from first extraction, and you get average time, its simply as 2+2

plus its more about hdd's speed, you should buy ssd to get real speed.

Am I not understanding how the quad processors work?

It's quad-core, not quad-processor...

adamf · Dec 30, 2012

startas said:
ProtoType said:

plus its more about hdd's speed, you should buy ssd to get real speed.

Click to expand...

Exactly. Your bottleneck here is not processor it is IO. If you are decompressing a file then the IO subsystem will push data to the cpu as fast as it can and then write out the result. Generally your input file will be contiguous. The write is less interesting as normally it is buffered.

If you try to unzip 2 at the same time your disk is thrashing reading from file A, then B which are physically in different places on the disk. You'll get the same issue but less with ssd. It will always be quicker to unzip A and then B than both together if you only have one drive.

There is no way you will use 100% cpu unzipping a file as IO subsystem will never be able to supply the data fast enough on a normal PC.

theveterans · Dec 30, 2012

WinRAR's extraction can only use 1 core while its compression uses all cores. Someone correct me if I'm wrong: so even if you open 2 instances of WinRAR and extract 2 files, those two instances will have to share the same core (as extraction is not multi-threaded) and therfore slows your extraction down.

theveterans · Dec 30, 2012

The best way to test this is to monitor the CPU usage of your i5. If extracting 2 things simultaneously only gives ~ 25-30 % CPU, WinRAR obviously is putting 2 processes in the same core thus explaining the slowness you get.

adamf · Dec 30, 2012

No, you are wrong. If CPU is 25% what does that mean? What it does not mean is that one core is used. And if it is 30% how is that one core? One and a bit cores? No it means the CPU is not being given enough work.

The way CPU subsystem works, very simply, is that the job dispatcher (not WinRAR or any user process) will place a piece of work where (with a bit of luck) it will finish quickest. It is not that simple as it may look forward in the instruction chain to guess this. Neither you or I can do this - it is on the chip. If you think WinRAR can specify which core it would like to use then you are incorrect.

In any case for IO bound (that is where RAM or CPU is not causing the issue) you will never see CPU at 100%. If you see CPU at 100% then your performance issue is either with IO or memory.

In the case of disk thrashing or in fact any non computational process it is not the CPU.

Forget cores unless your CPU utilisation is close to 100% for your task. For a PC doing non scientific tasks (or perhaps compilation etc) it will not be. Certainly for unzipping a RAR it is IO.

Although I could be completely wrong as I'm making assumptions and have not tested it. This is based on larger systems I work on.

ProtoType · Dec 30, 2012

Thanks for the replies, Much helpful!

adamf · Dec 30, 2012

Do one at a time. Also if you are copying large files - copy the first then the second, not both together. If you don't (assuming you have input files only on one drive) your disk arm will be going up and down and just not providing the data required.

Applies to any small PC system where files are not split over multiple disk arms. Not a Win 8 issue really.

cheers, adam

molebo · Dec 30, 2012

fireberd said:
But to answer your question, I don't see any difference on most programs between the old Q6600 CPU system I had and the new systems I have - one with an i7 3770 and the other with an i5 3550. .

so how come I get around 7k ppd with a q6600 and 29k with a i7 2600k ? the i7-2600k proceed 4 time more than the old q6600 in folding. Photoshop will proceed image twice faster with the Sandy Bridge vs Q6600 and Video Encoding is 3 time faster on the Sandy compare to the q6600, I can't see how you don't see a difference.

adamf · Dec 30, 2012

@molebo

The question is how your system is configured. If you are doing repetitive calculations on a small subset of data and you have enough RAM then a faster CPU will make things faster. The OS will bring into memory anything it needs to repeatedly access and this is far faster than going to disk (of whatever type - sdd, hdd, san whatever). If not you need to page it in from disk.

If as the OP said unzipping a rar is slower - this is because it can not be brought into memory - it is read processed and written.

Assuming you have enough memory then compilations, encodings etc will be faster with faster CPU. Copying a file will not be.

The only bottlenecks on any system are RAM, IO and CPU. It depends what you are doing but if CPU is not 100% then the bottleneck is elsewhere.

theveterans · Dec 30, 2012

adamf said:
No, you are wrong. If CPU is 25% what does that mean? What it does not mean is that one core is used. And if it is 30% how is that one core? One and a bit cores? No it means the CPU is not being given enough work. ....

Forget cores unless your CPU utilisation is close to 100% for your task. For a PC doing non scientific tasks (or perhaps compilation etc) it will not be. Certainly for unzipping a RAR it is IO.

Although I could be completely wrong as I'm making assumptions and have not tested it. This is based on larger systems I work on.

What I mean by 30 % cpu is that Winrar fully utilizes 1 core (~ 25% CPU reported by task manager) while some background process or you are listening to music while WinRAR is extracting for example, CPU usage will likely get a bit higher than 25% as shown by task manager. Not all "file sectors" [not sure if that is the correct word] inside a RAR file are actually compressed so extracting them require no CPU at all and thus the IO becomes the bottleneck for the most part.

i5 Extracting and WinRar

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