Are there operations that vector processors are inherently worse at or much harder to program for? Nowadays they seem to be mainly used for specialized tasks like graphics and machine learning accelerators, but given the expansion of SIMD instruction sets, are general purpose vector CPUs in the pipeline anywhere?
The road to Zettalinux
81–90 of 199 posts
Re: The road to Zettalinux
#82The section about 128-bit pointers being necessary for expanded memory sizes is unconvincing -- 64 bits provides 16 EiB (16 x 1024 x 1024 x 1024 x 1 GiB), which is the sort of address space you might need for byte-level addressing of a warehouse full of high-density HDDs. Memory sizes don't grow like they used to, and it's difficult to imagine what kind of new physics would let someone fit that many bytes into a mach…
> it's difficult to imagine what kind of new physics would let someone fit that many bytes into a machine that's practical to control with a single Linux kernel instance. I nominally agree with most of your post. But I should note that modern systems seem to be moving towards a "one pointer space" for the entire cluster. For example, 8 GPUs + 2 CPUs would share the same virtual memory space (GPU#1 may take one slice,…
I agree with you.
And seeing datacenter after datacenter shooting up like mushrooms, there might be some sort of abstraction running in this direction, that makes 128bit addresses feasible. At the moment 64bit seems like paging in this sense.
Re: The road to Zettalinux
#83I would think by now any bunch of clever people would be trying to fix the generalized problem of supporting n-bit memory addressing instead of continually solving the single problem of "how do we go from n*2 to (n+1)*2". I guess it's more practical to just let the next generation of kernel maintainers go through all of this hullabaloo again in 2090.
Re: The road to Zettalinux
#84There was a post awhile back from NASA saying how many digits of Pi they actually need [1]. import math pi = 31415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066…
The size of required data types is mostly orthogonal to the size of memory addresses or filesystem offsets.
Re: The road to Zettalinux
#85The section about 128-bit pointers being necessary for expanded memory sizes is unconvincing -- 64 bits provides 16 EiB (16 x 1024 x 1024 x 1024 x 1 GiB), which is the sort of address space you might need for byte-level addressing of a warehouse full of high-density HDDs. Memory sizes don't grow like they used to, and it's difficult to imagine what kind of new physics would let someone fit that many bytes into a mach…
So 64 bit address is only 1024 16TB HDDs? That number may go down quickly. There is a 100TB SSD already.
As my siblings are pointing out your error they are not addressing what you are saying. You are absolutely correct. It's conceivable within a few years to fit this much storage in one device (might be a full rack full of disks but still).
Re: The road to Zettalinux
#86There was a post awhile back from NASA saying how many digits of Pi they actually need [1]. import math pi = 31415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066…
The value of Pi you mention was the one in the question, the one in the answer is: > For JPL's highest accuracy calculations, which are for interplanetary navigation, we use 3.141592653589793. Let's look at this a little more closely to understand why we don't use more decimal places. I think we can even see that there are no physically realistic calculations scientists ever perform for which it is necessary to inclu…
Lol I should RTFA ;D
Re: The road to Zettalinux
#87> Matthew Wilcox took the stage to make the point that 64 bits may turn out to be too few — and sooner than we think Let's think critically for a moment. I grew up in the 1980s and 1990s, when we all craved more and more powerful computers. I even remember the years when each generation of video games was marketed as 8-bit, 16-bit, 32-bit, ect. BUT: We're hitting a point where, for what we use computers for, they're…
IMO there's an important distinction to be made between high-bit addressing and high-bit computing . Like, no one has enough memory to need more than 64 bits for addressing, and that is likely to remain the case for the foreseeable future. However, 128- and 256-bit values are commonly used in domains like graphics, audio, and so-on, where you need to apply long chains of transformations and filters, but retain as muc…
Those are data types, not pointer values or filesystem offsets. Totally different thing.
Re: The road to Zettalinux
#88There was a post awhile back from NASA saying how many digits of Pi they actually need [1]. import math pi = 31415926535897932384626433832795028841971693993751058209749445923078164062862089986280348253421170679821480865132823066470938446095505822317253594081284811174502841027019385211055596446229489549303819644288109756659334461284756482337867831652712019091456485669234603486104543266482133936072602491412737245870066…
The value of Pi you mention was the one in the question, the one in the answer is: > For JPL's highest accuracy calculations, which are for interplanetary navigation, we use 3.141592653589793. Let's look at this a little more closely to understand why we don't use more decimal places. I think we can even see that there are no physically realistic calculations scientists ever perform for which it is necessary to inclu…
I have horrid memories of debugging I had to do to get some god-awful fourier transform to calculate with 15 digits of precision to fit a spec. It's right at the boundary where double-precision stops being deterministic. Worst debugging week of my life.
Re: The road to Zettalinux
#89The section about 128-bit pointers being necessary for expanded memory sizes is unconvincing -- 64 bits provides 16 EiB (16 x 1024 x 1024 x 1024 x 1 GiB), which is the sort of address space you might need for byte-level addressing of a warehouse full of high-density HDDs. Memory sizes don't grow like they used to, and it's difficult to imagine what kind of new physics would let someone fit that many bytes into a mach…
Storage and interconnect specs are getting a lot faster. I could see a world where you treated an S3 scale storage system as a giant tiered addressable memory space. AS/400 systems sort of did something like that at a small scale.
Re: The road to Zettalinux
#90I remember a quote from the papers about Opal, an experimental OS that was intended to use h/w protection rather than virtual memory, so that all processes share the same address space and can just exchange pointers to share data.
"A 64 bit memory space is large enough that if a process allocated 1MB every second, it could continue doing this until significantly past the expected lifetime of the sun before it ran into problems"