Date: Thu, 09 Jun 2016 08:40:47 -0600 From: Ian Lepore <ian@freebsd.org> To: Warner Losh <wlosh@bsdimp.com>, Gergely Imreh <imrehg@gmail.com> Cc: FreeBSD ARM <freebsd-arm@freebsd.org> Subject: Re: RPi2 i/o blocking and SD card performance Message-ID: <1465483247.1188.60.camel@freebsd.org> In-Reply-To: <6406AECE-0153-494F-88EE-E58C8357FC1B@bsdimp.com> References: <CAJ3iQcoc5nVSFz3JKMG_Y9Q9k4PFizmp2rf3vfA7nv=u_12nBQ@mail.gmail.com> <6406AECE-0153-494F-88EE-E58C8357FC1B@bsdimp.com>
next in thread | previous in thread | raw e-mail | index | archive | help
On Thu, 2016-06-09 at 09:55 -0400, Warner Losh wrote: > > On Jun 9, 2016, at 5:37 AM, Gergely Imreh <imrehg@gmail.com> wrote: > > > > Hi, > > > > I've been testing FreeBSD 11.0-CURRENT on a RaspberryPi2. I'm relatively > > new to FreeBSD, and wondering if there's any advice for improving the > > performance a bit. > > > > First, it looks like there's a lot of i/o blocking behaviour going on. For > > example running MediaWiki on the board, if I compile any ports, the site > > itself is pretty much unusable (the PHP scripts time out even with 180s > > timeouts). The strangest thing is that the CPU usage is not at 100% all the > > way, can be that all 4 cores are ~99% idle, and still everything goes very > > slow. Once the ports compilation or any other i/o-related task is finished, > > it's snappy again. > > > > Any idea why it could be to have such big latency/lag even though the CPU > > is idle? Is there anything I could test? > > Whatÿs the HZ for the system? The sd/mmc system has a lot of context switches > may be one reason for this. What does HZ have to do with it? That's a serious question I've been asking for about 3 years now, and have not gotten an answer (any answer from anyone): "What influence does HZ have on modern freebsd?" (Modern meaning roughly "with eventtimers implemented and the ULE scheduler.") The little bit of testing I've tried to do hasn't shown any difference at all that I can detect between HZ=100 and HZ=5000, or any values inbetween. -- Ian
Want to link to this message? Use this URL: <https://mail-archive.FreeBSD.org/cgi/mid.cgi?1465483247.1188.60.camel>