Re: Need help with phys backed shm segments (Postgresql+FreeBSD).

Just as interesting

On Tue, 5 Dec 2000, Alfred Perlstein wrote:

> * Alfred Perlstein <bright@wintelcom.net> [001205 12:30] wrote:
> > * Tom Lane <tgl@sss.pgh.pa.us> [001205 08:37] wrote:
> > > BTW, I just remembered that in 7.0.*, the SLocks that are managed by
> > > SpinAcquire() all live in their own little shm segment.  On a machine
> > > where slock_t is char, it'd likely only amount to 128 bytes or so.
> > > Maybe you are seeing some bug in FreeBSD's handling of tiny shm
> > > segments?
> >
> > Good call, i think I found it! :)
>
> Here's the patch I'm using on FreeBSD, it seems to work, if any
> other FreeBSD'ers want to try it out, just apply the patch:
> cd /usr/src/sys/vm ; patch < patchfile
>
> and recompile and boot with a new kernel, then do this:
>
> sysctl -w kern.ipc.shm_use_phys=1
>
> or add:
> kern.ipc.shm_use_phys=1
> to /etc/sysctl.conf
>
> Let me know if it works.
>
> thanks,
> -Alfred
>
> Index: phys_pager.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/vm/phys_pager.c,v
> retrieving revision 1.3.2.1
> diff -u -u -r1.3.2.1 phys_pager.c
> --- phys_pager.c    2000/08/04 22:31:11    1.3.2.1
> +++ phys_pager.c    2000/12/05 20:13:25
> @@ -83,7 +83,7 @@
>           * Allocate object and associate it with the pager.
>           */
>          object = vm_object_allocate(OBJT_PHYS,
> -            OFF_TO_IDX(foff + size));
> +            OFF_TO_IDX(foff + PAGE_MASK + size));
>          object->handle = handle;
>          TAILQ_INSERT_TAIL(&phys_pager_object_list, object,
>              pager_object_list);
>
>

Randy Jonasz
Software Engineer
Click2net Inc.
Web:  http://www.click2net.com
Phone: (905) 271-3550

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