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List:       fedora-devel-list
Subject:    Re: Has something changed with RPMS?
From:       Adam Williamson <adamwill () fedoraproject ! org>
Date:       2020-06-03 15:02:51
Message-ID: 45b0fe34db61a77d098def95d40ff80d0292ef17.camel () fedoraproject ! org
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On Wed, 2020-06-03 at 10:46 +0300, Panu Matilainen wrote:
> 
> > > So this still seems kinda mysterious. Either somehow
> > > it wasn't fsync'ing before but it is now, or somehow disk writing
> > > performance on my system fell off a cliff?
> > > 
> > > I'll try and poke it some more tomorrow if I can, try some old kernels
> > > and/or old mock builds or something.
> > > 
> > 
> > Found it.
> > 
> > Nothing to do with databases, it's the new automatic SSD detection which 
> > also enables _flush_io to fsync files as we go during transactions. It 
> > does this on the grounds that it's good for the system otherwise (avoids 
> > trashing the caches and io peaks) and that it's not prohibitively 
> > expensive on SSD, but I guess this here quite clearly shows that it 
> > actually is.
> > 
> > Will fix shortly.
> 
> Okay, fixed in rpm-4.16.0-0.beta1.2 in rawhide.
> 
> For it to take effect though, the bootstrap-root needs to be updated (or 
> recreated). I don't know whether mock updates that automatically and if 
> it does, under what circumstances.
> 
> That's also how this all relates to the bootstrap stuff:
> When using mock without bootstrap, host rpm config is used. On Fedora < 
> 33 hosts, rpm doesn't automatically enable the io-flushing so things are 
> fast if not using bootstrap, or building for F < 33. And OTOH if running 
> from a rawhide host things would be slow unless you were building for F 
> < 33 with a bootstrap.
> 
> And that's also why you didn't need nosync before but suddenly it makes 
> a huge difference.

Wow, thanks a ton for looking into that and fixing it so quickly!
Really appreciate it. It sure would've taken me a lot longer to get
there :)
-- 
Adam Williamson
Fedora QA Community Monkey
IRC: adamw | Twitter: AdamW_Fedora | XMPP: adamw AT happyassassin . net
http://www.happyassassin.net
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