Can I use SMT with openMP? Eg, if I have 2 CPUs with SMT, the program runs with 4 threads?
Thanks! On Fri, May 19, 2023 at 11:52 AM Ishita Chaturvedi <ishi...@princeton.edu> wrote: > Hi Ayaz, > > Thank you for the link! > The problem here is twofold: > > 1. > > The APIC id doesn’t take into account the SMT thread. A possible fix > is here: > > https://github.com/darchr/gem5/pull/175/files#diff-e028a5adbd93f7a9858680f78fb405fbR282. > We need to have some way for the memory mapped address for the APIC > controller to be different for each thread. > 2. > > (And this one is much harder to solve) The TLB is shared between the > threads, but it’s not tagged per thread. So, even after solving (1), when > you run two different processes on the same core (on different threads), > they use the same virtual address, but *should* have different > physical addresses. However, the second thread will use the translations > for the first (what a bad security hole!). The solution here could be add > multiple TLBs (we’re hacking this up now) or, a better solution, would be > to add the ASID to the TLB entry tag. > > I think 1 should be straightforward. > I want to run the same process on both SMT threads. Will 2 still be an > issue? > I really need this for my research, and I would be grateful for any help > on this! > > Thank you, > Ishita > > On Fri, May 19, 2023 at 11:33 AM Ayaz Akram <yazak...@ucdavis.edu> wrote: > >> Hi Ishita, >> >> Regarding SMT in FS mode, you might find the discussion in the comments >> of the following JIRA issue helpful: >> >> [GEM5-332] SMT simulation in x86 is not supported - Jira (atlassian.net) >> <https://gem5.atlassian.net/browse/GEM5-332> >> >> -Ayaz >> >> On Thu, May 18, 2023 at 10:22 PM Ishita Chaturvedi via gem5-users < >> gem5-users@gem5.org> wrote: >> >>> Hi, >>> >>> I want to run SMT in FS mode, however, the support does not exist for it. >>> >>> Is there a reason for this support to not be available? Is it easy to >>> implement SMT in FS mode? >>> >>> Thanks! >>> _______________________________________________ >>> gem5-users mailing list -- gem5-users@gem5.org >>> To unsubscribe send an email to gem5-users-le...@gem5.org >>> >>
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