This sounds like you could start by unsetting WatchdogSec= for those daemons. Other than the watchdog, they shouldn't be using any CPU unless explicitly contacted.
On Wed, Jun 8, 2016, 02:50 Hebenstreit, Michael < michael.hebenstr...@intel.com> wrote: > The base system is actually pretty large (currently 1200 packages) - I > hate that myself. Still performance wise the packages are not the issue. > The SSDs used can easily handle that, and library loads are only happening > once at startup (where the difference van be measured, but if the runtime > is 24h startup time of 1s are not an issue). Kernel is tweaked, but those > changes are relatively small. > > The single problem biggest problem is OS noise. Aka every cycle that the > CPU(s) are working on anything but the application. This is caused by a > combination of "large number of nodes" and "tightly coupled job processes". > > Our current (RH6) based system runs with a minimal number of demons, none > of them taking up any CPU time unless they are used. Systemd process are > not so well behaved. After a few hours of running they are already at a few > seconds. On a single system - or systems working independent like server > farms - that is not an issue. On our systems each second lost is multiplied > by the number of nodes in the jobs (let's say 200, but it could also be up > to 10000 or more on large installations) due to tight coupling. If 3 demons > use 1s a day each (and this is realistic on Xeon Phi Knights Landing > systems), that's slowing down the performance by almost 1% (3 * 200 / 86400 > = 0.7% to be exact). And - we do not gain anything from those demons after > initial startup! > > My worst experience with such issues was on a cluster that lost 20% > application performance due to a badly configured crond demon. Now I do not > expect systemd to have such a negative impact, but even 1%, or even 0.5% of > expected loss are too much in our case. > > > -----Original Message----- > From: Jóhann B. Guðmundsson [mailto:johan...@gmail.com] > Sent: Wednesday, June 08, 2016 6:10 AM > To: Hebenstreit, Michael; Lennart Poettering > Cc: systemd-devel@lists.freedesktop.org > Subject: Re: [systemd-devel] question on special configuration case > > On 06/07/2016 10:17 PM, Hebenstreit, Michael wrote: > > > I understand this usage model cannot be compared to laptops or web > > servers. But basically you are saying systemd is not usable for our > > High Performance Computing usage case and I might better off by > > replacing it with sysinitV. I was hoping for some simpler solution, > > but if it's not possible then that's life. Will certainly make an > > interesting topic at HPC conferences :P > > I personally would be interesting comparing your legacy sysv init setup to > an systemd one since systemd is widely deployed on embedded devices with > minimal build ( systemd, udevd and journald ) where systemd footprint and > resource usage has been significantly reduced. > > Given that I have pretty much crawled in the entire mud bath that makes up > the core/baseOS layer in Fedora ( which RHEL and it's clone derive from ) > when I was working on integrating systemd in the distribution I'm also > interesting how you plan on making a minimal targeted base image which > installs and uses just what you need from that ( dependency ) mess without > having to rebuild those components first. ( I would think systemd > "tweaking" came after you had solved that problem first along with > rebuilding the kernel if your plan is to use just what you need ). > > JBG > _______________________________________________ > systemd-devel mailing list > systemd-devel@lists.freedesktop.org > https://lists.freedesktop.org/mailman/listinfo/systemd-devel >
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