Date: Tue, 30 Nov 2021 11:32:37 -0500 From: Shawn Webb <shawn.webb@hardenedbsd.org> To: Stefan Esser <se@freebsd.org> Cc: Joseph Mingrone <jrm@FreeBSD.org>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Call for Foundation-supported Project Ideas Message-ID: <20211130163237.hdfl7bsthccbxo7l@mutt-hbsd> In-Reply-To: <a81e3e4a-776b-0c58-3793-acabbb4fb148@freebsd.org> References: <861r36xzpe.fsf@phe.ftfl.ca> <a81e3e4a-776b-0c58-3793-acabbb4fb148@freebsd.org>
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--x37rvubhivh732aa Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Content-Transfer-Encoding: quoted-printable On Tue, Nov 30, 2021 at 12:53:20PM +0100, Stefan Esser wrote: > Am 23.11.21 um 23:41 schrieb Joseph Mingrone: > > Hello FreeBSD community, > >=20 > > The Foundation is seeking suggestions for new projects to support. What > > gaps in the Project are not being addressed by the broader community? >=20 > The "new" ULE scheduler has a number of well-known issues, which leads > to the "old" BSD scheduler giving better performance on many systems > and loads, but is based on concepts that made sense in pre-SMP times. >=20 > ULE suffers from pathological behavior in many scenarios, and it does > not know how to best deal with simultaneous multi-threading, big/little > architectures, or the effects of virtualization. >=20 > ULE does not care for the "niceness" of a process and lets nice -19 > processes run with hardly any reduction of the share of CPU cycles > granted compared to competing nice 0 processes, for example. >=20 > Virtualization gives a number of additional requirements and restrictions > in both the host and client. Schedulers in other operating systems have > been modified to reduce the risk of side-channel attacks by running only > processes for one user at a time on the virtual processors of an SMT core. >=20 > Within a virtual machine, the real topology of the underlying hardware > may be hidden and scheduling effects by the VM host may need to be taken > into consideration (e.g. clock variations and "time jumps"). There is > a connection to bhyve, at least (perhaps also to other virtualization > platforms) that has to be taken into account. >=20 > Another aspect is optimization for performance vs. optimization for > low power use, which both require a specific scheduling strategy on > complex CPU topologies. >=20 > IMHO, a scheduler design that is based on experiences gained by other > projects and our knowledge of deficiencies of the currently available > schedulers in FreeBSD under specific loads could be a huge win for the > project. >=20 > This would be a long-term project, and I do not see any developer > currently working on designing or implementing a new scheduler. >=20 > There have been minor changes to SCHED_ULE, recently, but I'd think > that a completely new design will be required, based on knowledge > gained in the last 1 or 2 decades and able to deal with architectural > changes that have occurred in that time frame. I also wonder how the recent push to big.little on multiple CPU architectures affects FreeBSD and how we could support it. Thanks, --=20 Shawn Webb Cofounder / Security Engineer HardenedBSD https://git.hardenedbsd.org/hardenedbsd/pubkeys/-/raw/master/Shawn_Webb/03A= 4CBEBB82EA5A67D9F3853FF2E67A277F8E1FA.pub.asc --x37rvubhivh732aa Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAABCAAdFiEEA6TL67gupaZ9nzhT/y5nonf44foFAmGmUiIACgkQ/y5nonf4 4forKg/+KPAYRJRx3csbecFMw7k6q+RMUn1Tn8Gf+SGzLvTltl0wMKOZqR/v3Wa3 MuOop1kTFBquT9rzdtlcxH9LkVoRyVjM4Vdm7lBQnRT2oyhe8R7EP7STlQV+wAlF ntRk9Mz1yj2c41/G+T7J3bRU2VW9fw3oMPXQ7s8Pe562oeD6kqifF8wZkQp3xFpv ZaZZ3YYVwuce7KEaA8whUjAhcZ2QnGHpOH1599BtNOC9sekgXKmx69MtJUa+eff/ YsZ70EzRLNa5rosbBY8fqojyNnJ6HuogC8HRn9RiId38LpiCv5g4ORDCENviD4Rv YDLO7ZSd0NdvaUzGFrvZSH6L1gZFeWuyiDy7UvNJJaBtvCtQrQrGvGzRn5HEjoPb k7ymZ1v4Wi0hZ/D3bFOdUat0TErnzSiY1ad9ssVKvSMk6mubLGlrfj9jv6AtGbV3 IqSbjMRmk5Pop6BiNhddF2ffOqkeAvNxHcr+HGcWO3oALAyCU/vmafFviM6TqI8o 9jpHB+WVOODP7VvshiwGkeWmutc/JRv3//RzW1rAIk8srlCTeZoB5bExbxPIbdqa 9oxNfdobA/HZ5cjtl6jWunO2+UcwrQ5DmzDo0hmw/RiEpYBMw1F4LQgjAmY8KiVd ELSByXV6wfMxr9HbsaSKoOdgawANT6oSVWOvUTDzG3yOs/5Op2Y= =fhGt -----END PGP SIGNATURE----- --x37rvubhivh732aa--
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