Date: Mon, 22 Oct 2007 17:59:04 -0700 From: Julian Elischer <julian@elischer.org> To: Ivan Voras <ivoras@freebsd.org> Cc: freebsd-current@freebsd.org Subject: Re: kthreads->kproc and back to kthread.. next patch Message-ID: <471D4758.2040209@elischer.org> In-Reply-To: <9bbcef730710221747w4d338e78mb9dbf5e2eb37908@mail.gmail.com> References: <471BDA2E.9040801@elischer.org> <ffijts$tqt$1@ger.gmane.org> <471D34D8.8020009@elischer.org> <9bbcef730710221747w4d338e78mb9dbf5e2eb37908@mail.gmail.com>
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Ivan Voras wrote: > On 23/10/2007, Julian Elischer <julian@elischer.org> wrote: > >> If you wanted to limit CPU usage for a particular group of threads it >> may be worth grouping them into a process and then you could have >> some control over them with 'nice'. > > Kernel processes can be niced? Nice :) So, for example, in theory I > could renice a geli thread that I don't want to eat much of my CPU > from the userland? maybe bu from memory NICE doesn't actually affect real-time threads :-) so it'd require the process to voluntarily take itself out of that class. It was just a random example type thought.. no-one actually has a use for that yet. > >> The AIO threads need to be processes because each of them needs >> a different address space that can be hacked to cover the address space of the >> process they are working for. > > Ok, this is why we used kprocs for them... > >> The Idle threads couldbe in their own process so you can easily see how much cpu idle.. > >> There are many other reasons you may want to group kernel threads. >> for example a single process with all teh interrupt threads in it might >> be useful for accounting for interupts in some ways. > > So, mostly cosmetics :) emphasis on MOSTLY in my original patch 2 years ago I changes nearly all the users of kthread_create to use the new one and only a few things went on using kproc_create(). AIO was one, and there were a couple of others that I didn't trust, so I left them. > > (don't get me wrong, I have nothing against kthreads<->kprocs :) ) Alan Cox is here next to me and we are discussing whether all the threads that are in the kernel should be put under PID 0 and have it called "kernel" instead of "swapper". It's swapper thread would be called "swapper" however.
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