Messages in this thread |  | | From | "Dan Maas" <> | Subject | Re: LMbench 2.4.0-test10pre-SMP vs. 2.2.18pre-SMP | Date | Tue, 24 Oct 2000 18:50:20 -0400 |
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> The pipe bandwidth is intimately related to pipe latency. Linux pipes > are fairly small (only 4kB worth of data buffer), so they need good > latency for good performance. ... > The pipe bandwidth could be fairly easily improved by just doubling the > buffer size (or by using VM tricks), but it's not been something that > anybody has felt was all that important in real life.
A while ago I hacked 2.2.17 to use larger pipe buffers. On my own pure throughput benchmark (two processes ping-pongging one buffer's worth of data on a single-CPU system), buffers larger than 4KB hardly gave any advantage. 64KB buffers were marginally (10-20%) faster, but performance dropped quite considerably after that (cache effects, maybe...).
After seeing these results I simply assumed that 4KB had been deliberately chosen as the optimal buffer size, rather than by luck =).
Now, Dave Miller's kiobuf pipes may change the picture somewhat...
Dan
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