Messages in this thread | | | Date | Mon, 2 Mar 2015 11:37:01 -0500 | From | Steven Rostedt <> | Subject | Re: [PATCH 07/15] mm: Add ___GFP_NOTRACE |
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On Mon, 2 Mar 2015 10:01:00 -0600 Tom Zanussi <tom.zanussi@linux.intel.com> wrote:
> Add a gfp flag that allows kmalloc() et al to be used in tracing > functions. > > The problem with using kmalloc for tracing is that the tracing > subsystem should be able to trace kmalloc itself, which it can't do > directly because of paths like kmalloc()->trace_kmalloc()->kmalloc() > or kmalloc()->trace_mm_page_alloc()->kmalloc().
This part I don't like at all. Why can't the memory be preallocated when the hist is created (the echo 'hist:...')?
kmalloc must never be called from any tracepoint callback.
This change is currently a showstopper.
-- Steve
> > With this flag, tracing code could use a special version of kmalloc() > that sets __GFP_NOTRACE on every allocation it does, while leaving the > normal kmalloc() path untouched. > > This would allow any tracepoint in the kmalloc path to be avoided via > DEFINE_EVENT_CONDITION() redefinitions of those events, which check > for ___GFP_NOTRACE immediately in their execution and break if set, > thereby avoiding the recursion. >
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