Date: Mon, 7 Oct 2013 20:10:18 +0200
From: Andi Kleen <andi@firstfloor.org>
To: "Suzuki K. Poulose" <suzuki@in.ibm.com>
Cc: Andi Kleen <andi@firstfloor.org>,
        Janani Venkataraman <jananive@in.ibm.com>,
        linux-kernel@vger.kernel.org, amwang@redhat.com, rdunlap@xenotime.net,
        aravinda@linux.vnet.ibm.com, hch@lst.de, mhiramat@redhat.com,
        jeremy.fitzhardinge@citrix.com, xemul@parallels.com,
        suzuki@linux.vnet.ibm.com, kosaki.motohiro@jp.fujitsu.com,
        adobriyan@gmail.com, tarundsk@linux.vnet.ibm.com, vapier@gentoo.org,
        roland@hack.frob.com, tj@kernel.org, ananth@linux.vnet.ibm.com,
        gorcunov@openvz.org, avagin@openvz.org, oleg@redhat.com,
        eparis@redhat.com, d.hatayama@jp.fujitsu.com, james.hogan@imgtec.com,
        akpm@linux-foundation.org, torvalds@linux-foundation.org
Subject: Re: [RFC] [PATCH 00/19] Non disruptive application core dump
 infrastructure using task_work_add()
Message-ID: <20131007181018.GL6882@two.firstfloor.org>
References: <20131004102532.1612.24185.stgit@f19-x64>
 <20131004134421.GG6882@two.firstfloor.org>
 <52524FAA.1030901@in.ibm.com>
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> > Couldn't they just use the new process_vm_readv() syscalls instead?
> > AFAIK those do not require ptrace.
> > 
> We need the register set and hence would need a ptrace.

But the kernel needs to stop to to read the registers.

Do you have data how much the latency difference is between
an optimized ptrace reader (using PTRACE_GETREGSET) vs the kernel ?

-Andi
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