Net Llama offered this little gem:
% I'm building 2.4.6 (yes, the final is out!) and ran across the option
% under Networking Options for "Packet socket: mmapped IO". The
% description sounds nice "If you say Y here, the Packet protocol driver
% will use an IO mechanism that results in faster communication. If
% unsure say NO".
%
% OK...so if this is such a great thing, why would i say NO? I honestly
% don't even understand what it does. Would there be any benefit to
% activating this for a ppp dialup connection? Any risks?
mmapped packet socket IO only buys you great benefits if you use
the packet socket stuff. But, to break it down somewhat, mmapped IO
is I/O to a memory map, an in-core image of a disk file. Obviously,
I/O to memory is vastly faster than I/O to disk, and an mmapped file
doesn't update the disk version until explicitly flushed (bdflush,
for example, doesn't update the on-disk file). Most modern "cat"
implementations, for example, use mmaps (memory maps), rather than
long sequences of disk reads followed by writes to stdout. You won't
see the difference for small files, but compare the performance of
catting, say, a 10MB file, to reading that same file in using vi.
I'm still sorting out the packet socket stuff, I'm afraid.
% I still haven't figured out why Netscape & Mozilla get sluggish under
% 2.4.x kenels, so i'm kinda grasping at straws for solutions.
Netscape and Mozilla are still broken, and the new VM code in the
kernel hasn't helped. I've no problems with Opera in this regard.
Kurt
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