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Message-Id: <20081216101804.eccda780.akpm@linux-foundation.org>
Date: Tue, 16 Dec 2008 10:18:04 -0800
From: Andrew Morton <akpm@...ux-foundation.org>
To: Ingo Molnar <mingo@...e.hu>
Cc: Markus Metzger <markus.t.metzger@...el.com>,
Peter Zijlstra <a.p.zijlstra@...llo.nl>,
linux-kernel@...r.kernel.org, tglx@...utronix.de, hpa@...or.com,
markus.t.metzger@...il.com, roland@...hat.com,
eranian@...glemail.com
Subject: Re: [rfc] x86, ptrace: memory accounting for branch tracing
On Tue, 16 Dec 2008 18:30:59 +0100 Ingo Molnar <mingo@...e.hu> wrote:
>
> * Markus Metzger <markus.t.metzger@...el.com> wrote:
>
> > Account memory allocated for the BTS buffer to the traced task's
> > total_vm and locked_vm.
>
> Andrew, is this the right (and preferred) way to attach BTS buffer
> allocation overhead to the RLIMIT_MEMLOCK bucket:
Close. I suspect we could refactor mlock.c to avoid all the code
duplication we have there.
There's (almost) nothing BTS-specific in this code, and it would be
better if it lived in mm/mlock.c. Hopefully in a
usable-by-other-parts-of-mlock.c fashion.
> > +static int ptrace_bts_allocate_buffer(struct task_struct *child, size_t size)
> > +{
> > + unsigned long rlim, vm, pgsz;
> > + int error = -ENOMEM;
> > +
> > + pgsz = PAGE_ALIGN(size) >> PAGE_SHIFT;
> > +
> > + down_write(&child->mm->mmap_sem);
> > +
> > + rlim = child->signal->rlim[RLIMIT_AS].rlim_cur >> PAGE_SHIFT;
> > + vm = child->mm->total_vm + pgsz;
> > + if (rlim < vm)
This is off-by-one, I think. Should be
if (vm > rmlim)
> > + goto out;
> > +
> > + rlim = child->signal->rlim[RLIMIT_MEMLOCK].rlim_cur >> PAGE_SHIFT;
> > + vm = child->mm->locked_vm + pgsz;
> > + if (rlim < vm)
ditto
> > + goto out;
> > +
> > + child->bts_buffer = kzalloc(size, GFP_KERNEL);
> > + if (!child->bts_buffer)
> > + goto out;
> > +
> > + child->bts_size = size;
> > +
> > + child->mm->total_vm += pgsz;
> > + child->mm->locked_vm += pgsz;
> > +
> > + error = 0;
> > + out:
> > + up_write(&child->mm->mmap_sem);
> > + return error;
>
> ?
>
> Ingo
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