From the LKML post linked in the story, it seems it's because some 4MiB pages (I couldn't understand why 4KiB pages aren't affected, if they effectively are not) are allocated for the AGP (GART more specifically) with some bits set telling it is cacheable.
Why would somebody want to cache the AGP memory? I'm pretty sure it's used 99.99% of the time as write-only memory, because it's the main output method of most computers. What's the point of caching that? It can only prevent the use of the CPU cache by some more important things, no?
Feel free to correct me if I'm wrong, I'm not very familiar with the usage of AGP memory (or GARTs).
Excuse my ignorance, but what the heck are "MiB" and "KiB" ??
Mibibytes and kibibytes. They refer to 2^20 and 2^10 bytes, respectively. (I.e., what many other people call megabytes and kilobytes.)
The scientific community had decided on SI unit prefixes like 100 years ago. "Mega" means 10^6 and "kilo" means 10^3. The computer science people came along and said "no, those will be powers of two for us." These units are a (probably futile) attempt to correct that particular stupidity.
I think it won't work out, because there's too much legacy stuff that there will always be confusion at this point about what "mega" and "kilo" mean with computers. Besides, "mibi" and "kibi" sound stupid enough that they'll probably never catch on.
They won't catch on if nobody uses them, as Divx showed us (not the one you're using, the other, older one). But I still think that these units are better, if only resulting in better advertisement from the HD makers.
"I think it won't work out, because there's too much legacy stuff that there will always be confusion at this point about what "mega" and "kilo" mean with computers."
Not to mention the fact that computers are incapable of "thinking" in anything but a power of two. You will not find a discrete quantity of 10 (or a power thereof) bytes anywhere in a computer system. This makes the SI units useless for computers. While re-defining them for use in computers was and still is an abuse, the lack of applicability of the conventional SI units makes it largely a non-issue. The only people who care are are HDD manufacturers who rate drives in "millions of bytes" so they can swindle stupid customers.
"A verbal contract isn't worth the paper it's printed on."
- Samuel Goldwyn
Don't cache it then! (Score:4, Insightful)
Why would somebody want to cache the AGP memory? I'm pretty sure it's used 99.99% of the time as write-only memory, because it's the main output method of most computers. What's the point of caching that? It can only prevent the use of the CPU cache by some more important things, no?
Feel free to correct me if I'm wrong, I'm not very familiar with the usage of AGP memory (or GARTs).
Re:Don't cache it then! (Score:2)
T
Re:Don't cache it then! (Score:1)
Mibibytes and kibibytes. They refer to 2^20 and 2^10 bytes, respectively. (I.e., what many other people call megabytes and kilobytes.)
The scientific community had decided on SI unit prefixes like 100 years ago. "Mega" means 10^6 and "kilo" means 10^3. The computer science people came along and said "no, those will be powers of two for us." These units are a (probably futile) attempt to correct that particular stupidity.
I think it won't work out, because there's too much legacy stuff that there will always be confusion at this point about what "mega" and "kilo" mean with computers. Besides, "mibi" and "kibi" sound stupid enough that they'll probably never catch on.
Re:Don't cache it then! (Score:1)
Re:Don't cache it then! (Score:2)
T
Re:Don't cache it then! (Score:2)
Powers of two (Score:2)
Not to mention the fact that computers are incapable of "thinking" in anything but a power of two. You will not find a discrete quantity of 10 (or a power thereof) bytes anywhere in a computer system. This makes the SI units useless for computers. While re-defining them for use in computers was and still is an abuse, the lack of applicability of the conventional SI units makes it largely a non-issue. The only people who care are are HDD manufacturers who rate drives in "millions of bytes" so they can swindle stupid customers.