On Fri, Jun 01, 2012 at 04:42:52AM +0000, Eitan Adler wrote: > Author: eadler > Date: Fri Jun 1 04:42:52 2012 > New Revision: 236380 > URL: http://svn.freebsd.org/changeset/base/236380 > > Log: > Add sysctl to query amount of swap space free > > PR: kern/166780 > Submitted by: Radim Kolar <h...@sendmail.cz> > Approved by: cperciva > MFC after: 1 week > > Modified: > head/sys/vm/swap_pager.c The commit messages lack any rationale for the change.
The rationale specified in the PR is wrong, there _is_ the sysctl
interface to read the swap use, vm.swap_info.N. It is used by e.g.
swapinfo(8)/libkvm(3) on live system.
>
> Modified: head/sys/vm/swap_pager.c
> ==============================================================================
> --- head/sys/vm/swap_pager.c Fri Jun 1 04:34:49 2012 (r236379)
> +++ head/sys/vm/swap_pager.c Fri Jun 1 04:42:52 2012 (r236380)
> @@ -2692,3 +2692,18 @@ swaponvp(struct thread *td, struct vnode
> NODEV);
> return (0);
> }
> +
> +static int
> +sysctl_vm_swap_free(SYSCTL_HANDLER_ARGS) {
> + int swap_free, used;
> + int total;
> +
> + swap_pager_status(&total, &used);
> +
> + swap_free = (total - used) * PAGE_SIZE;
> + return SYSCTL_OUT(req, &swap_free, sizeof(swap_free));
> +}
This just overflows at swap sizes greater then 2GB.
> +
> +SYSCTL_OID(_vm, OID_AUTO, swap_free, CTLTYPE_INT|CTLFLAG_RD|CTLFLAG_MPSAFE,
> + NULL, 0, sysctl_vm_swap_free, "Q",
> + "Blocks of free swap storage.");
Please revert the commit.
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