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Date: Sun, 1 Jan 2012 18:12:10 +0200 From: Gilad Ben-Yossef <gilad@...yossef.com> To: Avi Kivity <avi@...hat.com> Cc: Pekka Enberg <penberg@...nel.org>, linux-kernel@...r.kernel.org, Chris Metcalf <cmetcalf@...era.com>, Peter Zijlstra <a.p.zijlstra@...llo.nl>, Frederic Weisbecker <fweisbec@...il.com>, Russell King <linux@....linux.org.uk>, linux-mm@...ck.org, Matt Mackall <mpm@...enic.com>, Sasha Levin <levinsasha928@...il.com>, Rik van Riel <riel@...hat.com>, Andi Kleen <andi@...stfloor.org>, apkm@...ux-foundation.org Subject: Re: [PATCH v4 4/5] slub: Only IPI CPUs that have per cpu obj to flush On Sun, Jan 1, 2012 at 2:41 PM, Avi Kivity <avi@...hat.com> wrote: > On 11/23/2011 08:23 AM, Pekka Enberg wrote: >> On Tue, 22 Nov 2011, Gilad Ben-Yossef wrote: >>> static void flush_all(struct kmem_cache *s) >>> { >>> - on_each_cpu(flush_cpu_slab, s, 1); >>> + cpumask_var_t cpus; >>> + struct kmem_cache_cpu *c; >>> + int cpu; >>> + >>> + if (likely(zalloc_cpumask_var(&cpus, GFP_ATOMIC))) { >> >> __GFP_NOWARN too maybe? >> >>> + for_each_online_cpu(cpu) { >>> + c = per_cpu_ptr(s->cpu_slab, cpu); >>> + if (c->page) >>> + cpumask_set_cpu(cpu, cpus); >>> + } >>> + on_each_cpu_mask(cpus, flush_cpu_slab, s, 1); >>> + free_cpumask_var(cpus); >>> + } else >>> + on_each_cpu(flush_cpu_slab, s, 1); >>> } >> > > Since this seems to be a common pattern, how about: > > zalloc_cpumask_var_or_all_online_cpus(&cpus, GFTP_ATOMIC); > ... > free_cpumask_var(cpus); > > The long-named function at the top of the block either returns a newly > allocated zeroed cpumask, or a static cpumask with all online cpus set. > The code in the middle is only allowed to set bits in the cpumask > (should be the common usage). free_cpumask_var() needs to check whether > the freed object is the static variable. Thanks for the feedback and advice! I totally agree the repeating pattern needs abstracting. I ended up chosing to try a different abstraction though - basically a wrapper on_each_cpu_cond that gets a predicate function to run per CPU to build the mask to send the IPI to. It seems cleaner to me not having to mess with free_cpumask_var and it abstracts more of the general pattern. I intend to run the new code through some more testing tomorrow and send out V5 of the patch set. I'd be delighted if you can have a look through it then. Thanks! Gilad -- Gilad Ben-Yossef Chief Coffee Drinker gilad@...yossef.com Israel Cell: +972-52-8260388 US Cell: +1-973-8260388 http://benyossef.com "Unfortunately, cache misses are an equal opportunity pain provider." -- Mike Galbraith, LKML -- 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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