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- All processes go into the same array of queues, with different scheduling classes using different portions of the array. This allows user processes to have their priorities propogated up into interrupt thread range if need be. - I chose 64 run queues as an arbitrary number that is greater than 32. We used to have 4 separate arrays of 32 queues each, so this may not be optimal. The new run queue code was written with this in mind; changing the number of run queues only requires changing constants in runq.h and adjusting the priority levels. - The new run queue code takes the run queue as a parameter. This is intended to be used to create per-cpu run queues. Implement wrappers for compatibility with the old interface which pass in the global run queue structure. - Group the priority level, user priority, native priority (before propogation) and the scheduling class into a struct priority. - Change any hard coded priority levels that I found to use symbolic constants (TTIPRI and TTOPRI). - Remove the curpriority global variable and use that of curproc. This was used to detect when a process' priority had lowered and it should yield. We now effectively yield on every interrupt. - Activate propogate_priority(). It should now have the desired effect without needing to also propogate the scheduling class. - Temporarily comment out the call to vm_page_zero_idle() in the idle loop. It interfered with propogate_priority() because the idle process needed to do a non-blocking acquire of Giant and then other processes would try to propogate their priority onto it. The idle process should not do anything except idle. vm_page_zero_idle() will return in the form of an idle priority kernel thread which is woken up at apprioriate times by the vm system. - Update struct kinfo_proc to the new priority interface. Deliberately change its size by adjusting the spare fields. It remained the same size, but the layout has changed, so userland processes that use it would parse the data incorrectly. The size constraint should really be changed to an arbitrary version number. Also add a debug.sizeof sysctl node for struct kinfo_proc. |
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| .. | ||
| ffs_alloc.c | ||
| ffs_balloc.c | ||
| ffs_extern.h | ||
| ffs_inode.c | ||
| ffs_snapshot.c | ||
| ffs_softdep_stub.c | ||
| ffs_softdep.c | ||
| ffs_subr.c | ||
| ffs_tables.c | ||
| ffs_vfsops.c | ||
| ffs_vnops.c | ||
| fs.h | ||
| README.snapshot | ||
| README.softupdates | ||
| softdep.h | ||
$FreeBSD$ Using Soft Updates To enable the soft updates feature in your kernel, add option SOFTUPDATES to your kernel configuration. Once you are running a kernel with soft update support, you need to enable it for whichever filesystems you wish to run with the soft update policy. This is done with the -n option to tunefs(8) on the UNMOUNTED filesystems, e.g. from single-user mode you'd do something like: tunefs -n enable /usr To permanently enable soft updates on the /usr filesystem (or at least until a corresponding ``tunefs -n disable'' is done). Soft Updates Copyright Restrictions As of June 2000 the restrictive copyright has been removed and replaced with a `Berkeley-style' copyright. The files implementing soft updates now reside in the sys/ufs/ffs directory and are compiled into the generic kernel by default. Soft Updates Status The soft updates code has been running in production on many systems for the past two years generally quite successfully. The two current sets of shortcomings are: 1) On filesystems that are chronically full, the two minute lag from the time a file is deleted until its free space shows up will result in premature filesystem full failures. This failure mode is most evident in small filesystems such as the root. For this reason, use of soft updates is not recommended on the root filesystem. 2) If your system routines runs parallel processes each of which remove many files, the kernel memory rate limiting code may not be able to slow removal operations to a level sustainable by the disk subsystem. The result is that the kernel runs out of memory and hangs. Both of these problems are being addressed, but have not yet been resolved. There are no other known problems at this time. How Soft Updates Work For more general information on soft updates, please see: http://www.mckusick.com/softdep/ http://www.ece.cmu.edu/~ganger/papers/CSE-TR-254-95/ -- Marshall Kirk McKusick <mckusick@mckusick.com> July 2000