> It sounds like you are complaining about how FreeBSD has implemented zfs in > the system rather than about zfs in general. These problems don't occur > under Solaris. Zfs and the kernel need to agree on how to allocate/free > memory, and it seems that Solaris is more advanced than FreeBSD in this > area. It is my understanding that FreeBSD offers special zfs tunables to > adjust zfs memory usage.
It may be FreeBSD specific, but note that I a not talking about the amount of memory dedicated to the ARC and how it balances with free memory on the system. I am talking about eviction policy. I could be wrong but I didn't think ZFS port made significant changes there. And note that part the of *point* of the ARC (at least according to the original paper, though it was a while since I read it), as opposed to a pure LRU, is to do some weighting on frequency of access, which is exactly consistent with what I'm observing (very quick eviction and/or lack of inserton of data, particularly in the face of unrelated long-term I/O having happened in the background). It would likely also be the desired behavior for longer-running homogenous disk access patterns where optimal use of cache over long period may be more important than immediately reacting to a changing access pattern. So it's not like there is no reason to believe this can be about ARC policy. Why would this *not* occurr on Solaris? It seems to me that it would imply the ARC was broken on Solaris, since it is not *supposed* to be a pure LRU by design. Again, there may very well be a FreeBSD specific issue here that is altering the behavior, and maybe the extremity of it that I am reporting is not supposed to be happening, but I believe the issue is more involved than what you're implying in your response. -- / Peter Schuller _______________________________________________ zfs-discuss mailing list zfs-discuss@opensolaris.org http://mail.opensolaris.org/mailman/listinfo/zfs-discuss
