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Message-ID: <863e9df20805220516x7e6cd4ecvc4e88e2d4ec62ed@mail.gmail.com>
Date: Thu, 22 May 2008 17:46:19 +0530
From: "Abhishek Sagar" <sagar.abhishek@gmail.com>
To: "Srinivasa DS" <srinivasa@in.ibm.com>
Subject: Re: [RFC] [PATCH] To improve kretprobe scalability
Cc: "Jim Keniston" <jkenisto@us.ibm.com>, linux-kernel@vger.kernel.org,
       "Andrew Morton" <akpm@linux-foundation.org>,
       "Ananth Mavinakayanahalli" <ananth@in.ibm.com>,
       "Masami Hiramatsu" <mhiramat@redhat.com>,
       "Srikar Dronamraju" <srikar@linux.vnet.ibm.com>
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On 5/22/08, Srinivasa DS <srinivasa@in.ibm.com> wrote:
>  There were ideas of storing kretprobe instances in task_struct to get rid
> of locking, but that would require extending task_struct

Wouldn't chaining of return instances in task_struct only increase its
size by sizeof(struct list_head) bytes?

> and catching each task exit, destroying its kretprobe instances.

Which is kind of stil done by (...or at least we have a precendent of
this issue's awareness) kprobe_flush_task().

> This makes code more invasive.

Ok.

>  But in this implementation (global hash table, hashed by task), we
>  lock only the current task's hash bucket and hence we have fairly low
> contention.

I may be underestimating the complexity of having returns instances
associated with current task_struct, but anything else seems counter
intuitive. There might be more possibilites to exploit the fact that
functions instances are per-task.

A step in the right direction nevertheless :-)

>  Thanks
>   Srinivasa DS
--
Regards,
Abhishek Sagar