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Date: Tue, 20 Oct 2009 16:39:01 +0900 From: Tejun Heo <tj@...nel.org> To: Eric Dumazet <eric.dumazet@...il.com> CC: Ingo Molnar <mingo@...e.hu>, Jiri Kosina <jkosina@...e.cz>, Jeff Mahoney <jeffm@...e.com>, Peter Zijlstra <peterz@...radead.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, Tony Luck <tony.luck@...el.com>, Fenghua Yu <fenghua.yu@...el.com>, linux-ia64@...r.kernel.org Subject: Re: Commit 34d76c41 causes linker errors on ia64 with NR_CPUS=4096 Eric Dumazet wrote: > Ingo Molnar a écrit : > >> Still looks like a bug if it causes a breakage (linker error) on IA64, >> and if the 'fix' (i'd call it a workaround) causes a (small but nonzero) >> performance regression on other architectures. >> > > True, but this also save some amount of ram for some distro kernels. > > If we keep this static NR_CPUS thing, we might be able to free > the end of table, for other per_cpu users ? > > if (nr_cpus_ids < NR_CPUS) { > per_cpu_free_static_zone(&update_shares_data[nr_cpus_ids], > sizeof(long)*(NR_CPUS - nr_cpus_ids)); > } That's doable but Considering that the users of NR_CPUS are pretty few (and should be kept that way), I think it would be better to just use dynamic allocation, which no longer incurs any major performance difference (the only difference is constant offset vs. pointer in a variable), for those cases. Thanks. -- tejun -- 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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