linux-kernel - Re: [RFC] [PATCH] To improve kretprobe scalability

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Message-ID: <863e9df20805220516x7e6cd4ecvc4e88e2d4ec62ed@mail.gmail.com>
Date:	Thu, 22 May 2008 17:46:19 +0530
From:	"Abhishek Sagar" <sagar.abhishek@...il.com>
To:	"Srinivasa DS" <srinivasa@...ibm.com>
Cc:	"Jim Keniston" <jkenisto@...ibm.com>, linux-kernel@...r.kernel.org,
	"Andrew Morton" <akpm@...ux-foundation.org>,
	"Ananth Mavinakayanahalli" <ananth@...ibm.com>,
	"Masami Hiramatsu" <mhiramat@...hat.com>,
	"Srikar Dronamraju" <srikar@...ux.vnet.ibm.com>
Subject: Re: [RFC] [PATCH] To improve kretprobe scalability

On 5/22/08, Srinivasa DS <srinivasa@...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
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