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Re: [Nmh-workers] Pessimal Optimizations.

2012-12-11 20:12:21

On 2012-12-11, at 6:04 PM, Ken Hornstein wrote:

So, think about the data flow for a second. mhl reads the body of the
message in (using m_getfld()!) and then writes it to a pipe. replyfilter
reads it from the pipe and then processes it.  So we're talking about
a stdio read, a copy from the stdio buffer to the mhl input buffer, then
write() results in a copy from the mhl input buffer to the kernel, and then
there is a copy from the kernel to replyfilter's input (not sure if that's
using stdio there).  So that's at least 4 copies.  I tested replyfilter out
with files in the tens of megabytes and I didn't notice any delay (the
bulk of the messages were attachments that replyfilter didn't output, but
it still had to read the whole message).  So yeah, that would have bogged
down 20 years ago, but not today.

Perhaps the optimization needed here isn't in the buffer copies, per se :-)

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