sysctl spinning (was: Re: ps Causes Hard Hang) (fwd)
Cy Schubert
Cy.Schubert at komquats.com
Thu Mar 4 22:30:30 PST 2004
So far so good, the problem appears to be fixed. I'll leave it in
production tonight. If I have any fallout tonight, I'll notify you tomorrow
morning.
Cheers,
--
Cy Schubert <Cy.Schubert at komquats.com> http://www.komquats.com/
BC Government . FreeBSD UNIX
Cy.Schubert at osg.gov.bc.ca . cy at FreeBSD.org
http://www.gov.bc.ca/ . http://www.FreeBSD.org/
------- Forwarded Message
Date: Thu, 04 Mar 2004 16:21:29 -0800
From: Cy Schubert <Cy.Schubert at komquats.com>
To: Don Lewis <truckman at freebsd.org>
cc: freebsd-current at freebsd.org
Subject: Re: sysctl spinning (was: Re: ps Causes Hard Hang)
In message <200403042142.i24LgS7E005323 at gw.catspoiler.org>, Don Lewis
writes:
> On 5 Mar, Bruce Evans wrote:
> > On Thu, 4 Mar 2004, Don Lewis wrote:
> >
> >> I just checked the mlock() man page in the Single UNIX Specification
> >> Version 3. Our mlock() implementation is broken. We should be
> >> returning ENOMEM here, though this will result in some sort of user
> >> visible sysctl breakage instead of a tight loop.
> >
> > POSIX is more authoritative. It says that ENOMEM may be returned if
> > an implementation-defined limit would be exceeded, and that EAGAIN
> > shall be returned if some or all of the memory could not be locked
> > when the call was made. So it literally requires returning EAGAIN
> > even when the limit would be exceeded, but it doesn't mean to require
> > that.
>
> That's the same as SUSv3.
>
> I was pretty frazzled when I sent my previous message and was thinking
> the test was something like:
> if (atop(size) > vm_page_max_wired)
>
> The following patch is probably better.
>
> Index: sys/vm/vm_mmap.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/vm/vm_mmap.c,v
> retrieving revision 1.181
> diff -u -r1.181 vm_mmap.c
> --- sys/vm/vm_mmap.c 1 Mar 2004 02:44:33 -0000 1.181
> +++ sys/vm/vm_mmap.c 4 Mar 2004 21:24:29 -0000
> @@ -923,8 +923,8 @@
> if (addr + size < addr)
> return (EINVAL);
>
> - if (atop(size) + cnt.v_wire_count > vm_page_max_wired)
> - return (EAGAIN);
> + if (atop(size) > vm_page_max_wired)
> + return (ENOMEM);
>
> PROC_LOCK(proc);
> if (size + ptoa(pmap_wired_count(vm_map_pmap(&proc->p_vmspace->vm_map))
> ) >
> @@ -933,6 +933,9 @@
> return (ENOMEM);
> }
> PROC_UNLOCK(proc);
> +
> + if (atop(size) + cnt.v_wire_count > vm_page_max_wired)
> + return (EAGAIN);
>
> error = vm_map_wire(&proc->p_vmspace->vm_map, addr,
> addr + size, VM_MAP_WIRE_USER|VM_MAP_WIRE_NOHOLES);
>
I'll give this a try tonight after my buildworld completes. I'll keep you
posted.
Cheers,
- --
Cy Schubert <Cy.Schubert at komquats.com> http://www.komquats.com/
BC Government . FreeBSD UNIX
Cy.Schubert at osg.gov.bc.ca . cy at FreeBSD.org
http://www.gov.bc.ca/ . http://www.FreeBSD.org/
------- End of Forwarded Message
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