Messages in this thread | | | Date | Wed, 20 Nov 2002 15:33:02 -0800 (PST) | From | Davide Libenzi <> | Subject | Re: [rfc] epoll interface change and glibc bits ... |
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On Wed, 20 Nov 2002, Jamie Lokier wrote:
> Davide Libenzi wrote: > > > > And the lower size of the structure will help to reduce the amount of > > > > memory transfered to userspace. I just saw that adding the extra "obj" > > > > member lowered performance of about 15% with crazy tests like Ben's > > > > pipetest. This because it creates, on my machine, more than 400000 events > > > > per second, and saving memory bandwidth on such conditions is a must. With > > > > the "more human" http test performance are about the same. > > > > > > I'd be quite surprised if 400,000 word/sec of memory bandwidth can > > > explain a 15% time difference, especially considering all the other > > > things that are done to communicate over a pipe (wakeups etc). > > > > Jamie, they were 16 bytes * 400000, and the token passed through the pipe > > was 12 bytes. > > However, it's 4 bytes (1 word) * 400000 _difference_ between the two > tests, yes?
Yep, the problem is that the "tool" used to measure ( Ben's pipetest ) on my machine has a variance of about 35% and this makes every measure prety fuzzy.
- Davide
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