[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] Re: [Xen-devel] [PATCH] sched_credit: Remove cpu argument to __runq_insert()
On Tue, 2015-11-03 at 05:38 -0700, Jan Beulich wrote: > > > > On 03.11.15 at 11:16, <George.Dunlap@xxxxxxxxxxxxx> wrote: > > So you agree that this change makes the source code make more sense > > ("looks like an improvement at the source level"), but you think > > that > > this will make the compiled code less efficient; and you recommend > > instead of making the source code clearer, to make things even > > *better* by changing the BUG_ON() to an ASSERT? > > > > Why do you think the compiler output will be less efficient? > > Due to the two extra memory references, which the compiler is > unlikely to be able to eliminate in all cases?. > Right. I had a quick look at the assembly code, and I think I saw something like that. As far as I've seen, though, the text sections of the generated binaries --with and without this patch-- were equally big (due to alignment, I think). Also, for the reasons explained here: http://lists.xen.org/archives/html/xen-devel/2015-11/msg00051.html As far as I'm concerned, this patch is: Acked-by: Dario Faggioli <dario.faggioli@xxxxxxxxxx> That being said... > > Overall I think the burden of proof is on you to show that the code > > as > > it is introduces a sufficient performance improvement over the more > > readable code, rather than on Harmandeep (or Dario or I) to show > > that > > it doesn't. > > Okay, so far I thought people suggesting a change are the ones > to prove that the change doesn't have undesirable effects. > ...just FTY, I probably will try having a look at what it means to make __runq_insert() non-inline. But that's another patch. :-) Thanks and Regards, Dario -- <<This happens because I choose it to happen!>> (Raistlin Majere) ----------------------------------------------------------------- Dario Faggioli, Ph.D, http://about.me/dario.faggioli Senior Software Engineer, Citrix Systems R&D Ltd., Cambridge (UK) Attachment:
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