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Message-Id: <200804142042.40109.vda.linux@googlemail.com> Date: Mon, 14 Apr 2008 20:42:40 +0200 From: Denys Vlasenko <vda.linux@...glemail.com> To: Andi Kleen <andi@...stfloor.org> Cc: Ingo Molnar <mingo@...e.hu>, linux-kernel@...r.kernel.org Subject: Re: Does process need to have a kernel-side stack all the time? On Monday 14 April 2008 19:44, Andi Kleen wrote: > > A lot of effort went into minimizing of stack usage. > > If I understand it correctly, one of the reasons for this > > was to be efficient and not have lots of pages > > used for stacks when we have a lot of threads > > (tens of thousands). > > Actually the real reason the 4K stacks were introduced IIRC was that > the VM is not very good at allocation of order > 0 pages and that only > using order 0 and not order 1 in normal operation prevented some stalls. > > This rationale also goes back to 2.4 (especially some of the early 2.4 > VMs were not very good) and the 2.6 VM is generally better and on > x86-64 I don't see much evidence that these stalls are a big problem > (but then x86-64 also has more lowmem). > > Note that your proposal doesn't change this at all. Actually, it does, because if you have only N*no_of_CPUs stacks, you can allocate them upfront, making fragmentation a non-issue. However, the proposal doesn't look viable anyway. -- vda -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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