On 12/21/2011 05:47 PM, Greg KH wrote: > On Wed, Dec 21, 2011 at 05:32:36PM -0800, Tim Bird wrote: >> On 12/21/2011 04:51 PM, Greg KH wrote: >>> On Wed, Dec 21, 2011 at 04:36:21PM -0800, Tim Bird wrote: >>>> On 12/21/2011 03:19 PM, Greg KH wrote: >> >>> Huh, I'm not talking about syslogd, I'm talking about the syslog(2) >>> syscall we have. >> >> OK - switching gears. Since the kernel log buffer isn't normally >> used to store use-space messages, I thought you were referring >> to syslog(3) and the associated (logger(1) and syslogd(8)). > > The kernel log buffer has been storing userspace messages for a while > now, look at your boot log on the latest Fedora and openSUSE releases > (or any other distro using systemd for booting). Sorry - I don't have a distro that uses systemd. I'm completely unaware of this use of the kernel log for user-space message logging. No wonder Lennart and Kay are so hot on making a new logging system. It seems sub-optimal to me, to intermingle a structured log with a pure-ASCII log. > Again, please see what we are already doing in the kernel and userspace, > I think a lot of the above is already implemented. I don't know what systemd has got going on in user-space. I'm looking at a very recent kernel, and I see no support for multiple log channels, or an optimized open/write path. Maybe Lennart could save me some time doing this research. Lennart, How does current systemd prevent user-space messages from crowding out kernel messages? (or vice-versa). Since you've been doing a lot of work on logging, do you have any existing metrics for logging overhead via the kernel log buffer? > Which brings me back to my original question, what does this code do, > that is not already present in the kernel, and why is a totally new > interface being proposed for it? At the least, it supports multiple log channels. Quite frankly my mind has been blown a bit by the suggestion to overload the kernel log buffer with user-space messages. I would never have gone that route. But I'll have to find out more about this systemd thing to answer your question. Secondly, this is not a particularly new or radical interface. It is new to legacy Linux, but it's been in the Android Linux kernel for some years now, and it has worked well. -- Tim ============================= Tim Bird Architecture Group Chair, CE Workgroup of the Linux Foundation Senior Staff Engineer, Sony Network Entertainment ============================= -- To unsubscribe from this list: send the line "unsubscribe linux-embedded" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
