Messages in this thread | | | From | Kay Sievers <> | Date | Fri, 7 Aug 2009 18:06:15 +0200 | Subject | Re: [PATCH] Driver Core: devtmpfs - kernel-maintained tmpfs-based /dev |
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On Fri, Aug 7, 2009 at 17:51, Chris Friesen<cfriesen@nortel.com> wrote: > Greg KH wrote: >> On Fri, Aug 07, 2009 at 08:04:08AM +0300, Al Boldi wrote: > >>> The question is, how fast can devtmpfs get the device list from the kernel on >>> bootup? How much faster than udev? How much slower than static /dev? >> >> It's much faster than udev, and is equivalent to a static /dev with the >> exception that the group and permission settings that you are used to. >> udev then needs to come along and make those settings, but that's so >> frickin fast it's amazing. > > Earlier in the thread you indicated a 0.5sec speedup over udev. Is that > really considered "much faster"?
The kernel boots up and mounts the root filesystem in less than a second these days. :)
> I do agree that it makes sense to do this, but more from an elegance > view than a performance one.
That's right. The possible speedups are mainly a side-effect of the simplicity we get by having the kernel providing us the the nodes without having hard userspace synchronization points early at bootup.
The init=/bin/sh with a fully working and correctly, regarding the dynamic major/minor numbers, populated /dev is alone reason enough to do that, I think.
Also things like "modprobe loop; losetup /dev/loop0" will just work, which do not work reliably today without waiting for userspace to create the nodes.
Kay -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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