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Re: copy faults from user_string* functions
- From: "Frank Ch. Eigler" <fche at redhat dot com>
- To: Eric Wong <normalperson at yhbt dot net>
- Cc: Systemtap List <systemtap at sourceware dot org>
- Date: Fri, 26 Jul 2013 20:22:22 -0400
- Subject: Re: copy faults from user_string* functions
- References: <20130726063634 dot GA32443 at dcvr dot yhbt dot net> <y0miozxmeqe dot fsf at fche dot csb> <20130726175602 dot GA5773 at dcvr dot yhbt dot net>
Hi, Eric -
On Fri, Jul 26, 2013 at 05:56:02PM +0000, Eric Wong wrote:
> [...]
> Is there any optional way to get stap to trigger page faults to get
> that data?
Not easily. Perhaps from the tracing site, the code could load a few
bytes of the strings whose addresses are being passed. Perhaps try an
mlock() or some other explicit data-segment-dereference loop during
program startup?
> When tracing, losing a little performance is OK, especially with
> cmogstored (which is entirely network/disk bound).
Understood.
- FChE