Messages in this thread | | | Date | Thu, 10 Mar 2011 08:00:32 -0800 | From | Andi Kleen <> | Subject | Re: [PATCH 0/5] make *_gate_vma accept mm_struct instead of task_struct |
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On Tue, Mar 08, 2011 at 07:31:56PM -0500, Stephen Wilson wrote: > > Morally, the question of whether an address lies in a gate vma should be asked > with respect to an mm, not a particular task. > > Practically, dropping the dependency on task_struct will help make current and > future operations on mm's more flexible and convenient. In particular, it > allows some code paths to avoid the need to hold task_lock. > > The only architecture this change impacts in any significant way is x86_64. > The principle change on that architecture is to mirror TIF_IA32 via > a new flag in mm_context_t.
The problem is -- you're adding a likely cache miss on mm_struct for every 32bit compat syscall now, even if they don't need mm_struct currently (and a lot of them do not) Unless there's a very good justification to make up for this performance issue elsewhere (including numbers) this seems like a bad idea.
> This is the first of a two part series that implements safe writes to > /proc/pid/mem. I will be posting the second series to lkml shortly. These
Making every syscall slower for /proc/pid/mem doesn't seem like a good tradeoff to me. Please solve this in some other way.
-Andi
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