Hi,
On Nov 29, 2007 9:02 AM, Pekka Enberg <[email protected]> wrote:
> > Is it really necessary to track every memory address? Tracking slab
> > objects would require far less memory. You might also want to make
> > kzalloc() and GFP_ZERO mark the memory area as initialized to avoid
> > some page faults.
On Thu, 29 Nov 2007, Vegard Nossum wrote:
> Yes, we are in fact only tracking the memory within SLUB allocations
> (minus what SLUB itself needs for bookkeeping -- like the caches).
Yeah but you didn't answer my question: why do we track every memory
address instead of slab objects? What's the benefit? Like I already said,
tracking slab objects would require much less memory which makes the
thing more practical. It also reduces the number of false positives (the
CONFIG_OPTIMIZE_FOR_SIZE problem). And we already have slab poisoning to
cover the cases we would not catch with this scheme.
On Thu, 29 Nov 2007, Vegard Nossum wrote:
> As for the kzalloc() and GFP_ZERO, I believe these will write zeros to
> the data in question before the memory is returned to the caller. In
> that case, the area will be "automatically" set to initialized since
> these writes are also intercepted by kmemcheck.
Yes, and what I proposed is as a potential optimization. Debugging aids
need to be fast enough to be practical.
Pekka
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