Subject: fsync performance hit on 1.6.1
To: Daniel Brewer <>
From: Stephen Ma <>
List: tech-kern
Date: 07/03/2003 06:07:30
>>>>> "Daniel" == Daniel Brewer <> writes:

Daniel> Hi When comparing our software's CPU utilization running on
Daniel> 151 & on 161, I noticed an inexplicably high usage on
Daniel> 161. After digging deeper with gprof, I found that an fsync on
Daniel> 161 takes significantly longer than on 151. Our software
Daniel> writes captured images into a ring buffer in a memory
Daniel> file-system, so other servers can retrieve them. Could someone
Daniel> explain the why fsync on 1.6.1 is so significantly slower than
Daniel> on 1.5.1? Is there a work-around? Or perhaps a completely
Daniel> different way of doing this?

This sounds like it would be the effect of PR kern/17321, which was
applied to 1.6.1. There's no work-around, but I don't see why you'd
need to use fsync() on a file stored on MFS...

- S