Date: Tue, 27 Jul 2010 21:29:56 +0200 From: Debacker <debackerl@gmail.com> To: Andrew Gould <andrewlylegould@gmail.com> Cc: freebsd-questions@freebsd.org Subject: Re: Real-Time Video Recording (ionice equivalent) Message-ID: <AANLkTimwplb2_HptPh0e6KEQnr4HqYxDPe5vD4Uw8OIf@mail.gmail.com> In-Reply-To: <AANLkTinQx3Myo06ed7Q7Ou_r3tepGGYQFbfhYNJbpa6T@mail.gmail.com> References: <AANLkTinqwCSzoCdEnrSoXN1jkpoIGmESgbMsI3JFB5YF@mail.gmail.com> <AANLkTinQx3Myo06ed7Q7Ou_r3tepGGYQFbfhYNJbpa6T@mail.gmail.com>
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Of course, just like you could put real-time processes in one CPU, and normal processes on another to avoid implement complex algorithms. While your solution is pragmatic, I would like to know if there are "clean" ways to do it. If not, this would be a documented use case to why would anyone actually need an I/O scheduler. Laurent On Tue, Jul 27, 2010 at 9:23 PM, Andrew Gould <andrewlylegould@gmail.com>wrote: > On Tue, Jul 27, 2010 at 1:45 PM, Debacker <debackerl@gmail.com> wrote: > > Hi, > > > > I'm looking for a ionice equivalent for FreeBSD. Let suppose that I setup > a > > NAS using FreeBSD. I can substain 50MiB/s writing. > > Let suppose that I have a 720p security camera, writing at 2 MiB/s in a > > file. Then I have 10 users copying files around. > > All of this activity (camera + users) through Samba, so each connection > has > > a dedicated process. > > > > Problem is that I want to give camera's maximal priority to guarantee > smooth > > recording. > > > > I don't expect Samba to use much CPU, 99% should be spent in IO. So if I > set > > the nice value of camera's process to Real-Time, it should do much, > because > > its process will be on wait status most of the time. > > Consequently, when some IO requests coming from camera's process are in > the > > queue, I want them to have top priority compared to requests coming from > > other processes. > > As the camera is limited to 2MiB/s, I expect the system to remain > > responsive. > > > > I know that seeks may lower the speed of the HDD, but as the HDD is > slowing > > down, completing requests, I expect the number of camera IO requests to > > increase in the queue, and to be packed together, hopefully, stabilizing > the > > number of seeks. > > > > BTW, I would use "root preexec" setting of Samba to execute a shell > script > > for each new connection, giving best priority to the process if the user > is > > "camera". > > > > Any idea? > > > > Thanks > > > > Laurent Debacker > > Would putting the camera's storage space on a separate HDD from the > other users help? > > Andrew >
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