On Wed, 21 Mar 2007, Jens Axboe wrote: > On Tue, Mar 20 2007, Davide Libenzi wrote: > > > > I was looking at Jens FIO stuff, and I decided to cook a quick patch for > > FIO to support GUASI (Generic Userspace Asyncronous Syscall Interface): > > > > http://www.xmailserver.org/guasi-lib.html > > > > I then ran a few tests on my Dual Opteron 252 with SATA drives (sata_nv) > > and 8GB of RAM. > > Mind that I'm not FIO expert, like at all, but I got some interesting > > results when comparing GUASI with libaio at 8/1000/10000 depths. > > If I read those result correctly (Jens may help), GUASI output is more > > then double the libaio one. > > Lots of context switches, yes. But the throughput looks like 2+ times. > > Can someone try to repeat the measures and/or spot the error? > > Or tell me which other tests to run? > > This is kinda a suprise for me ... > > I don't know guasi at all, but libaio requires O_DIRECT to be async. I'm > sure you know this, but you may not know that fio default to buffered IO > so you have to tell it to use O_DIRECT :-) > > So try adding a --direct=1 (or --buffered=0, same thing) as an extra > option when comparing depths > 1.
I knew about AIO and O_DIRECT, but I thought FIO was using it by default :) I used it for the first time yesterday night, and there are a pretty wide set of options. Will re-run today with --direct. I was pretty surprised though. Since libaio was matching with syslets, I was thinking that a userspace version using a queue-always design (hard to do the cachehit optimization if you're not inside the scheduler ;), was going to be considerably slower. > I'll add your guasi engine, but disable it. Unfortunately fio still > doesn't have a nifty configure setup, so these things are still > manual... Well, you do have your own HAVE_*, you just need to make autoconf/automake do the checks for you. Of course, then you'll be pissed every time an autoconf/automake update break your setup, but lately it seems to be going better. Really :) - Davide - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [EMAIL PROTECTED] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
