Date: Sat, 26 Aug 2017 12:47:40 -0700 (PDT) From: Don Lewis <truckman@FreeBSD.org> To: kostikbel@gmail.com Cc: freebsd-rwg@pdx.rh.CN85.dnsmgr.net, avg@freebsd.org, freebsd-arch@freebsd.org Subject: Re: ULE steal_idle questions Message-ID: <201708261947.v7QJle5Q054291@gw.catspoiler.org> In-Reply-To: <20170826184650.GS1700@kib.kiev.ua>
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On 26 Aug, Konstantin Belousov wrote: > On Sat, Aug 26, 2017 at 11:29:29AM -0700, Don Lewis wrote: >> I actually haven't noticed that problem on my package build boxes. I've >> experienced decent interactive performance even when the load average is >> in the 60 to 80 range. I also have poudriere configured to use tmpfs >> and the only issue I run into is when it starts getting heavily into >> swap (like 20G) and I leave my session idle for a while, which lets my >> shell and sshd get swapped out. Then it takes them a while to wake up >> again. Once they are paged in, then things feel snappy again. This is >> remote access, so I can't comment on what X11 feels like. > > I believe what people complain about is the following scenario: > they have some interactive long living process, say firefox or mplayer. > The process' threads consume CPU cycles, so the ULE interactivity > detection logic actually classifies the threads as non-interactive. > > This is not much problematic until a parallel build starts where > toolchain processes are typically short-lived. This makes them > classified as interactive, and their dynamic priority are lower than the > priority of long-lived threads which are interactive by user perception. > > I did not analyzed the KTR dumps but this explanation more or less > coincides with the system slugginess when attempt to use mplayer while > heavily oversubscribed build (e.g. make -j 10 on 4 cores x 2 SMT > machine) is started. I can believe that. I keep an excessive number of tabs open in firefox and it would frequenty get into a state where it would consume 100% of a CPU core. Very recent versions of firefox are a lot better. Xorg is another possible victim. I've just noticed that when certain windows have mouse focus (firefox being one, wish-based apps are another) that the Xorg %CPU goes to 80%-90%. I think this crept in with the lastest MATE upgrade. If Xorg is treated as non-interactive, then the desktop experience is going to be less than optimal if there is competing load.
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