On Wed, Nov 11, 2009 at 06:57:20PM +0100, ????? ???????????? wrote:
> Why should this class only available for kernel threads? There are
> daemons ported from micro kernel platforms which act like a kernel
> daemon but run in user land and could benefit from such a scheduler
> class.
Because it is modeled on the SYS class, which is also not available to
user threads. Supporting user threads involves a bunch of additional
work which isn't relevant to the problem at hand.
Cheers,
- jonathan
> On Wed, Nov 11, 2009 at 1:00 AM, Darren J Moffat
> <darrenm at sac.sfbay.sun.com> wrote:
> > I'm submitting this as closed approved automatic, it has already been
> > reviewed by core ZFS and kernel scheduling teams. Given the taxonomy
> > of the new interfaces I believe this is sufficient review and closed
> > approved automatic is sufficient. If any member disagrees then I'll
> > set a fast-track timer.
> >
> > Template Version: @(#)sac_nextcase 1.68 02/23/09 SMI
> > This information is Copyright 2009 Sun Microsystems
> > 1. Introduction
> > 1.1. Project/Component Working Name:
> > System Duty Cycle Scheduling Class and ZFS IO Observability
> > 1.2. Name of Document Author/Supplier:
> > Author: Jonathan Adams
> > 1.3 Date of This Document:
> > 10 November, 2009
> > 4. Technical Description
> >
> > This case covers two user-visible changes associated with the bug:
> >
> > 6806882 need a less brutal I/O scheduler
> >
> > The changes are:
> >
> > 1. A new kernel-thread-only scheduling class, SDC
> > (System Duty Cycle) is introduced. Since the
> > list of scheduling classes is user-visible through
> > dispadmin(1M) and priocntl(1), we feel an ARC case
> > is appropriate.
> >
> > The new scheduling class is only used by kernel threads,
> > so the only manpage changes are a new SDC(7) page covering
> > the existence of the new loadable module, and an update
> > to the discussion of the SYS class in priocntl(2).
> >
> > A new function "sysdc_thread_enter()", puts a kernel thread
> > into SDC.
> >
> > 2. In order to improve the observability of ZFS IO processing,
> > we introduce a new system process per-zpool, with a
> > u_comm and u_psargs of zpool-<poolname> (i.e. zpool-foo).
> > The LWPs in the process are kernel threads associated
> > with IO processing. Since these threads have LWPs, they
> > get microstate accounting data. Thus, CPU usage associated
> > with IO processing can be observed using prstat(1M) and ps(1).
> >
> > This process will always be in the global zone, even if
> > the pool was imported into a local zone.
> >
> > These changes, while user-visible, are essentially implementation
> > details, and are not committed interfaces. We've tried to make this
> > clear in the manpage changes.
> >
> >
> > Interface Table
> > ---------------
> >
> > Interface Stability
> > --------------------------------------- -----------------
> > SDC module and scheduling class Consolidation Private
> > sysdc_thread_enter() Consolidation Private
> > zpool-<poolname> process Volatile
> >
> > We seek Micro/Patch binding for these interfaces.
> >
> > See Also
> > --------
> >
> > 6806882 need a less brutal I/O scheduler
> >
> >
> > Man Page Diffs
> > --------------
> >
> > SDC(7)
> > +Device and Network Interfaces SDC(7)
> > +
> > +
> > +NAME
> > + SDC - System Duty Cycle scheduling class
> > +
> > +DESCRIPTION
> > + The System Duty Cycle (SDC) scheduling class is used for some
> > + CPU-intensive kernel thread workloads. Like the SYS class,
> > + it cannot be used for user processes.
> > +
> > +ATTRIBUTES
> > + See attributes(5) for descriptions of the following attri-
> > + butes:
> > + ____________________________________________________________
> > + | ATTRIBUTE TYPE | ATTRIBUTE VALUE |
> > + |_____________________________|_____________________________|
> > +
> > +SEE ALSO
> > + attributes(5)
> > +
> >
> > priocntl(2)
> > ...
> > that class and/or when setting class-specific scheduling
> > parameters.
> >
> > Two special scheduling classes, SYS and SDC, exist for the purpose of
> > |
> > scheduling the execution of certain special system processes
> > (such as the swapper process). It is not possible to change
> > the class of any LWP to SYS or SDC. In addition, any processes in
> > |
> > the SYS or SDC classes that are included in a specified set of
> > |
> > processes are disregarded by priocntl(). For example, an
> > idtype of P_UID and an id value of 0 would specify all
> > processes with a user ID of 0 except processes in the SYS and
> > |
> > SDC classes and (if changing the parameters using PC_SETPARMS or
> > |
> > PC_SETXPARMS) the init(1M) process.
> > ...
> >
> > zpool(1M)
> > --- zpool.1m.dist Tue Nov 3 14:00:53 2009
> > +++ zpool.1m Tue Nov 3 14:49:47 2009
> > @@ -947,6 +947,15 @@
> > version number, and only up to the most
> > recent version supported by this software.
> >
> > +PROCESSES
> > + Each imported pool has an associated process, named
> > + zpool-poolname. The threads in this process are the
> > + pool's IO processing threads, which handle the compression,
> > + checksumming, and other tasks for all IO associated with the
> > + pool. This process exists to provides visibility into the CPU
> > + utilization of the system's storage pools. The existence
> > + of this process is an unstable interface.
> > +
> > EXAMPLES
> > Example 1 Creating a RAID-Z Storage Pool
> >
> >
> > 6. Resources and Schedule
> > 6.4. Steering Committee requested information
> > 6.4.1. Consolidation C-team Name:
> > On
> > 6.5. ARC review type: Automatic
> > 6.6. ARC Exposure: open
> >
> > _______________________________________________
> > opensolaris-arc mailing list
> > opensolaris-arc at opensolaris.org
> >
>
>
>
> --
> , _ _ ,
> { \/`o;====- Olga Kryzhanovska -====;o`\/ }
> .----'-/`-/ olga.kryzhanovska at gmail.com \-`\-'----.
> `'-..-| / Solaris/BSD//C/C++ programmer \ |-..-'`
> /\/\ /\/\
> `--` `--`
