linux-kernel - Re: [PATCH 2/4] kmemleak: Handle percpu memory allocation

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Message-ID: <20111004091314.GF15637@dhcp-172-17-108-109.mtv.corp.google.com>
Date:	Tue, 4 Oct 2011 02:13:14 -0700
From:	Tejun Heo <htejun@...il.com>
To:	Catalin Marinas <catalin.marinas@....com>
Cc:	"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>,
	Huajun Li <huajun.li.lee@...il.com>,
	Christoph Lameter <cl@...ux-foundation.org>
Subject: Re: [PATCH 2/4] kmemleak: Handle percpu memory allocation

Hello,

On Tue, Oct 04, 2011 at 10:04:46AM +0100, Catalin Marinas wrote:
> > The percpu part looks fine to me but I don't know how kmemleak works
> > to judge whether the kmemleak part is okay or not.  This just avoids
> > false positives from slab and would still require bumping up the early
> > log memory as # of cpus increases, right?
> 
> No, there is only one kmemleak call for each __percpu pointer (to the
> specific kmemleak_*_percpu function). The kmemleak expands the percpu
> pointer into corresponding blocks for each cpu but the early log only
> stores a single call.

Hmmm... but the following definitely seems O(#PCPU_ALLOCS * #CPUS)?
What am I missing?

+/*
+ * Log an early allocated block and populate the stack trace.
+ */
+static void early_alloc_percpu(struct early_log *log)
+{
+       unsigned int cpu;
+       const void __percpu *ptr = log->ptr;
+
+       for_each_possible_cpu(cpu) {
+               log->ptr = per_cpu_ptr(ptr, cpu);
+               early_alloc(log);
+       }
+}

Thanks.

-- 
tejun
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