Date: Sun, 29 Apr 2012 14:27:32 +0200 From: Oliver Pinter <oliver.pntr@gmail.com> To: Alexander Motin <mav@freebsd.org> Cc: Davide Italiano <davide@freebsd.org>, Albert Shih <Albert.Shih@obspm.fr>, Luigi Rizzo <rizzo@iet.unipi.it>, freebsd-stable@freebsd.org, Ian Smith <smithi@nimnet.asn.au> Subject: Re: High load event idl. Message-ID: <CAPjTQNGesMffKZupENy0YWjC8LToutCyHh9uGqd-XKTN24goew@mail.gmail.com> In-Reply-To: <4F9D2F0C.4050501@FreeBSD.org> References: <20120427203013.GB60961@pcjas.obspm.fr> <CAPjTQNFsHZQLp8oMwhjkAWLnYZ5mPv9kr9=X5GhqHqExoHM0yw@mail.gmail.com> <20120427213459.GA61125@pcjas.obspm.fr> <4F9B946D.3030607@FreeBSD.org> <CAPjTQNGts290DyjORNfir8_rZ5S_vdog%2BJMEBA9mc2vJhUa=jg@mail.gmail.com> <4F9CCEF2.6050609@FreeBSD.org> <20120429155512.M91148@sola.nimnet.asn.au> <4F9CDE91.1060300@FreeBSD.org> <CAPjTQNF=0Hgq_7BxeK_8o6DRQ%2BUJ_r94Y3PqwF8f_ccDeA_hHQ@mail.gmail.com> <4F9D2F0C.4050501@FreeBSD.org>
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http://oliverp.teteny.bme.hu/freebsd/ktr/ On 4/29/12, Alexander Motin <mav@freebsd.org> wrote: > On 04/29/12 15:04, Oliver Pinter wrote: >> Removing dummynet from kernel don't chanage anything, that is releated >> to load average. The loadavg hold to 0.70 +/- 0.2. (single user : sh + >> top) > > New ktr dump? > >> On 4/29/12, Alexander Motin<mav@freebsd.org> wrote: >>> On 04/29/12 09:09, Ian Smith wrote: >>>> On Sun, 29 Apr 2012 08:17:38 +0300, Alexander Motin wrote: >>>> > On 04/29/12 01:53, Oliver Pinter wrote: >>>> > > Attached the ktr file. This is on core2duo P9400 cpu ( >>>> > > smbios.system.product="HP ProBook 5310m (WD792EA#ABU)" ). >>>> The >>>> workload >>>> > > is only a single user boost: sh + top running, but the load >>>> average is >>>> > > near 0.5. >>>> > >>>> > ktr shows no real load there. But it shows that you are using >>>> dummynet, that >>>> > schedules its runs on every hardclock tick. I believe that load >>>> you >>>> see is >>>> > the result or synchronization between dummynet calls and loadvg >>>> sampling, >>>> > both of which called from hardclock. I think removing dummynet >>>> from >>>> equation, >>>> > should hide this problem and also reduce you laptops power >>>> consumption. >>>> > >>>> > What's about fixing this, it is loadavg sampling algorithm that >>>> should be >>>> > changed. Fixing dummynet to not run on every hardclock tick >>>> would >>>> also be >>>> > great. >>>> >>>> Wading in out of my depth, and copying Luigi in case he misses it .. >>>> but >>>> even back in the olden days when HZ defaulted to 100, one was advised >>>> to >>>> use HZ>= 1000 for smooth dummynet traffic shaping dispatch scheduling. >>>> >>>> I wonder, with the newer clocks and timers, whether there is another >>>> clock that could be used for dummynet scheduling, that would not have >>>> this effect (even if largely cosmetic?) on load average calculation? >>> >>> First of all, the easiest solution would be to make dummynet to schedule >>> callout not automatically, but on first queued packet. I believe that in >>> case of laptop the queue should be empty most of time and the callout >>> calls are completely useless there. Luigi promised to look on this once. >>> >>> What's about better precision/removing synchronization -- there is >>> starting GSoC project now (by davide@) to rewrite callout(9) subsystem >>> to use better precision allowed by new timer drivers. While now it is >>> possible to get raw access to additional timer hardware available on >>> some systems, I don't think it is a good idea. > > > -- > Alexander Motin >
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