Re: sysctl spinning (was: Re: ps Causes Hard Hang) (fwd)

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
> _at__at_ -923,8 +923,8 _at__at_
>  	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))
> ) >
> _at__at_ -933,6 +933,9 _at__at_
>  		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/



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