anyone understand torvald's critique of freebsd?
cswiger at mac.com
Sun Apr 23 02:50:29 UTC 2006
Ted Mittelstaedt wrote:
> Then why does Linus think manipulating the VM page table mappings
> is bad? That is, why does he -really- think it's bad, not the
> publically-given reason? Is it because Linux is extrordinairly
> inefficient in page table mappings due to some structural decision
> that Linus made that cannot be reversed now, that it could never
> be any good at it? Or is there some other reason?
I can't speak with certainty as to what someone else might think; no doubt Linus
is entirely capable of explaining his own position should you wish to inquire,
I think Linus doesn't care much for Zero-copy sockets because for the common
case of 1500/1504-byte MTU, you end up wasting at least 60% of a 4096-byte page
for each packet, and maybe ?three? times that much if your hardware splits the
packet into separate pages for the mbuf header, the packet headers, and the
I think FreeBSD doesn't enable Zero-copy sockets by default because those are
legitimate criticisms, but there is some interest and potential for benefits
from them, at least for some other circumstances like jumbo ethernet frames.
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