Date: Sat, 21 May 2005 18:59:36 -0700 From: Colin Percival <cperciva@freebsd.org> To: Marcel Moolenaar <marcel@xcllnt.net> Cc: freebsd-arch@freebsd.org Subject: Re: Scheduler fixes for hyperthreading Message-ID: <428FE788.8020408@freebsd.org> In-Reply-To: <9e8314b53980a379445cc8c07086901d@xcllnt.net> References: <428FC00B.3080909@freebsd.org> <aef05e1ae6104223181ad3cf03e11390@xcllnt.net> <428FD710.4060200@freebsd.org> <9e8314b53980a379445cc8c07086901d@xcllnt.net>
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Marcel Moolenaar wrote: > On May 21, 2005, at 5:49 PM, Colin Percival wrote: >> Put simply, threads which share a processor core can monitor each others' >> memory access patterns, so we need to ensure that such co-scheduling >> never >> happens between threads which have different privileges. > > I'll be studying your paper to see if it can be shown that the HT > implementation in Itanium is affected as well. My understanding is that there are no currently released ia64 processors with hyperthreading support, but that some future ia64 processor(s) are likely to be affected. > I can only assume that the discussion was i386 centric (as this is > typically the case). Hence my request for a problem description. In addition to i386 and amd64, which are certainly affected, and ia64, which will probably be affected, there is a good chance that some powerpc processors are affected... the problem is a general one with shared caches and probably affects all currently existing simultaneous multithreading processors. I think the "right solution" is to make the basic functionality machine independent, but have the machine dependent initialization code determine which sets of threads share caches. Colin Percival
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