Date: Tue, 30 Nov 2021 12:53:20 +0100 From: Stefan Esser <se@freebsd.org> To: Joseph Mingrone <jrm@FreeBSD.org>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Subject: Re: Call for Foundation-supported Project Ideas Message-ID: <a81e3e4a-776b-0c58-3793-acabbb4fb148@freebsd.org> In-Reply-To: <861r36xzpe.fsf@phe.ftfl.ca> References: <861r36xzpe.fsf@phe.ftfl.ca>
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This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --------------8X4XvH4ckeU4gxW3O270aypK Content-Type: multipart/mixed; boundary="------------SB1EV19uYbJkmCPSY0AgS0xL"; protected-headers="v1" From: Stefan Esser <se@freebsd.org> To: Joseph Mingrone <jrm@FreeBSD.org>, FreeBSD Hackers <freebsd-hackers@freebsd.org> Message-ID: <a81e3e4a-776b-0c58-3793-acabbb4fb148@freebsd.org> Subject: Re: Call for Foundation-supported Project Ideas References: <861r36xzpe.fsf@phe.ftfl.ca> In-Reply-To: <861r36xzpe.fsf@phe.ftfl.ca> --------------SB1EV19uYbJkmCPSY0AgS0xL Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: quoted-printable Am 23.11.21 um 23:41 schrieb Joseph Mingrone: > Hello FreeBSD community, >=20 > The Foundation is seeking suggestions for new projects to support. Wha= t > gaps in the Project are not being addressed by the broader community? 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. 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. 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. 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= =2E 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. Another aspect is optimization for performance vs. optimization for low power use, which both require a specific scheduling strategy on complex CPU topologies. 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. This would be a long-term project, and I do not see any developer currently working on designing or implementing a new scheduler. 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. Regards, STefan --------------SB1EV19uYbJkmCPSY0AgS0xL-- --------------8X4XvH4ckeU4gxW3O270aypK Content-Type: application/pgp-signature; name="OpenPGP_signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="OpenPGP_signature" -----BEGIN PGP SIGNATURE----- wsB5BAABCAAjFiEEo3HqZZwL7MgrcVMTR+u171r99UQFAmGmELAFAwAAAAAACgkQR+u171r99UTs +wgAxxfH21oG1Z6P9YHXIvy2dg1IPWo9AvFmFq2NWF5wmqLkvymGSIcorsd0f0b5xNx1y7pWripl PmVRQgMobwNNNLLVWazOkAXEzHBPZJULwsCqLj0FvMwgQ5H6WSprs8I9C8WGwHUPMhhdEp4r+bYG X7IPHJZsfhS9KHdlX0+NvX4SD3C4jbz1fXaMYFb3rC1QoxSlnodmrnsAo7C+Oon4gGa/CLpTDhdj w9VxujPC/3SA/m80jl/z4MWVAu5RBorTv0j2Nskag524Zvr1YgznSCNwt0efgOnMyqo2my56PbMF PFBEiJqJEcAmjwf8gVdLknXqkEhDynB5sLHUPWUT7A== =fs4t -----END PGP SIGNATURE----- --------------8X4XvH4ckeU4gxW3O270aypK--
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