Is there an easy way to change the I/O priority of a whole group of processes the way renice -g does? It seems like only changing the I/O priority of a single process is supported by ionice. If this can't be done, can someone please point me to the the relevant API calls (I'm not at all familiar with the POSIX api) so that I can write a quick command line utility to implement this functionality myself?
When I renice a multithreaded process in Ubuntu 10.04, then view the results in top, it seems that only the main thread actually gets reniced. All the other threads retain their old nice value. What's the easiest way to renice all threads in a process instead of just the main thread?
I'm running a setup consisting of a Linux host OS and a Windows 7 guest (VMware Workstation). I'm trying to run 16 CPU-bound background jobs on the Linux host at nice values of 19 (the lowest possible priority; one for each virtual CPU) and simultaneously use the Windows VM as a normal desktop OS. For some reason the Linux background jobs make my Windows VM grind to a halt even though VMware's nice value is 0.
If it helps, I'm running an 8-core machine with hyperthreading, so 16 virtual CPUs. Since VMware Workstation only supports virtualizing 8 cores, only 8 of the cores are visible in the Windows guest.
Edit: The background jobs I'm running are almost purely CPU bound and perform virtually no I/O.
Edit # 2: It's not an issue with hyperthreading messing up scheduling. Disabling hyperthreading in the BIOS solves nothing.
How much overhead does x86/x64 virtualization (I'll probably be using VirtualBox, possbly VMWare, definitely not paravirtualization) have for each of the following operations a Win64 host and Linux64 guest using Intel hardware virtualization?
Purely CPU-bound, user mode 64-bit code
Purely CPU-bound, user mode 32-bit code
File I/O to the hard drive (I care mostly about throughput, not latency)
Network I/O
Thread synchronization primitives (mutexes, semaphores, condition variables)
Thread context switches
Atomic operations (using the lock prefix, things like compare-and-swap)
I'm primarily interested in the hardware assisted x64 case (both Intel and AMD) but wouldn't mind hearing about the unassisted binary translation and x86 (i.e. 32-bit host and guest) cases, too. I'm not interested in paravirtualization.
In Unix-like OS's, what's the point of giving the owner of a file anything less than 7 (rwx) for file permissions? The owner can trivially change the owner permissions for his/her files, and so can a cracker if the acct. is compromised. Setting the owner permission to anything other than 7 seems to just get in the way w/o producing any actual security improvements.
On Linux (and other Unix-like OS's if there's a general answer), is there an easy way to get an output similar to the time command (current real time, user, and system CPU usage totals) for a process that is still running?