On Sat, May 04, 2019 at 07:00:30PM +0200, Markus Gothe wrote: > Ouch, then fork()'ing is indeed an issue. And Linux not being an RTOS is > another issue, but I hope you are using an RTOS (like QNX or FreeRTOS) and > not Linux.
Oh, Linux is actually a better match for a full blown IVI system, at least for the application processor part. You just have to be a bit more careful when configuring the system. :) > As pointed out the whole Linux hotplugging system is the real issue here and > something like mdevd would be the answer. It's actually only a problem when you use the naive /proc/sys/kernel/hotplug approach. Running mdev as daemon solves most of the issues. And given the small size of the patch I thought it would be a valuable amendment to busybox. mdevd also looks quite nice but it's another dependency. Regards, Jan > > //M > > Sent from my BlackBerry — the most secure mobile device > > > Original Message > > > > From: [email protected] > Sent: 4 May 2019 10:49 > To: [email protected] > Cc: [email protected] > Subject: Re: [PATCH 0/3] mdev: add daemon mode > > > On Fri, May 03, 2019 at 11:16:34PM +0200, Markus Gothe wrote: > > Err, zram ofc :) > ... > > > > Or even better you could turn on zswap on your embedded device and avoid > > the OOM-kiler which I guess is the real reason you fixed this. > > Actually RAM was not the problem at all. It really was the time to spawn > all the processes and the overhead to serialize them. > > > Actually I want to know when this happens that the kernel creates that many > > hotplug events; seems like the issue is somewhere else. > > We're building an IVI (In Vehicle Infotainment) system that needs to > boot really fast. For example we have to show a rear view camera in 2s > from cold boot. To achive this the kernel is kept very small and most of > the drivers are loaded as modules when they are actually needed. This > alone creates so many events that the impact is measurable. > > Regards, > Jan > > > > > //M > > > > Sent from my BlackBerry — the most secure mobile device > > > > > > Original Message > > > > > > > > From: [email protected] > > Sent: 3 May 2019 23:03 > > To: [email protected] > > Subject: [PATCH 0/3] mdev: add daemon mode > > > > > > If mdev is used as kernel hotplug helper and the system generates many > > hotplug events it will quickly consume considerable resources because a > > process is forked for each event and, if the mdev.seq feature is used, > > they must also coordinate among each other. While the uevent applet > > mitigates some of the resource problems you still have to pay the cost > > for a fork/exec and parsing of mdev.conf for each event. > > > > The following patches add an optional daemon mode to mdev that let's > > mdev listen on a netlink socket for kernel hotplug events. This mode > > works much like udev and avoids the fork/exec/parse overhead on many > > events. > > > > > > _______________________________________________ > > busybox mailing list > > [email protected] > > http://lists.busybox.net/mailman/listinfo/busybox _______________________________________________ busybox mailing list [email protected] http://lists.busybox.net/mailman/listinfo/busybox
