On Wed, 29 Mar 2006, Dag-Erling Smørgrav wrote:
"Conrad J. Sabatier" <[EMAIL PROTECTED]> writes:
Chris <[EMAIL PROTECTED]> wrote:
so [kern.ipc.nmbclusters] has no affect, has this become a read only
tunable again only settable in loader.conf?
To the best of my knowledge, this has *always* been a loader tunable,
not configurable on-the-fly.
kern.ipc.nmbclusters is normally computed at boot time. A compile- time
option to override it was introduced in 2.0-CURRENT. At that time, it was
defined in param.c. A read-only sysctl was introduced in 3.0-CURRENT. It
moved from param.c to uipc_mbuf.c in 4.0-CURRENT, then to subr_mbuf.c when
mballoc was introduced in 5.0-CURRENT; became a tunable at some point after
that; then moved again to kern_mbuf.c when mballoc was replaced with mbuma
in 6.0-CURRENT. That is the point where it became read-write, for no good
reason that I can see; setting it at runtime has no effect, because the size
of the mbuf zone is determined at boot time. Perhaps Bosko (who wrote both
mballoc and mbuma, IIRC) knows.
Paul Saab from Yahoo! has a set of patches that allow run-time nmbclusters
changes to be implemented -- while it won't cause the freeing of clusters
referenced, it goes through and recalculates dependent variables, propagates
them into UMA, etc. I believe they're running with this patch on 6.x, and I
expect that they will be merged to -CURRENT and -STABLE in the relatively near
future. Not before 6.1, however.
If the nmbclusters setting really has no effect right now, we should mark the
sysctl as read-only to make it more clear it doesn't, since allowing it to be
set without taking effect is counter-intuitive.
Robert N M Watson
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