From mboxrd@z Thu Jan 1 00:00:00 1970 MIME-Version: 1.0 In-Reply-To: <2f40e8ca50e83137d89718948b1b2c4b@brasstown.quanstro.net> References: <2f40e8ca50e83137d89718948b1b2c4b@brasstown.quanstro.net> From: Jessica Yu Date: Tue, 27 May 2014 14:15:01 -0400 Message-ID: To: Fans of the OS Plan 9 from Bell Labs <9fans@9fans.net> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Subject: Re: [9fans] nix scheduler changes Topicbox-Message-UUID: f23f3b16-ead8-11e9-9d60-3106f5b1d025 On Mon, May 26, 2014 at 1:14 PM, erik quanstrom wro= te: > so, i've done a little bit more work characterizing the performance > of the scheduler correctness changes, and i know have some understanding > on why e.g. ping times are a bit slower. > > the old code essentially let processor 0 spin in runproc, other processor= s called > halt. the new code uses monmwait to wait for a change on all processors. > this has some significant impacts on performance and power use. for exam= ple, > on my test box with 4c/8t: > > spin/halt monmwait spin/monmwait > ping 8=C2=B5s 14=C2=B5s 8=C2=B5s = # ip/ping -n10 $sysname > mk 6.26s 3.98s 3.80 # make nix = kernel > fans audible silent audible > =CE=B4power - -24w 0 # r= esolution =3D .1A =3D 12w @ 120v) > > this seems to indicate the latency is all in runproc(), and not waiting f= or things > to be ready and assuming they will be has a big performance boost. > > (the third column, testing spin on mach 0, plus monmwait on the others wa= s done > to tell if monmwait has high latency or not.) > > i'd really be interested to see what this does on 24c/48t machines. some= thing > tells me the performance impacts would be huge, and different. > > - erik > > --- > ps. hzsched in the distribution is 10% off for HZ=3D100, since > schedticks =3D m->ticks + HZ/10, and delaysched tests > for > not the expected >=3D. > Nice. Excited to see how a cleaned up + simplified runproc() and the per-Mach queues could also change things. Any reason why the ping test w/ monmwait wasn't consistent with the performance improvement in other areas?