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Re: [RFC][PATCH 2/2] uprobes: single-step out of line
- From: Ernie Petrides <petrides at redhat dot com>
- To: Jim Keniston <jkenisto at us dot ibm dot com>
- Cc: "Frank Ch. Eigler" <fche at redhat dot com>, Linda Wang <lwang at redhat dot com>, Ernie Petrides <petrides at redhat dot com>, systemtap at sources dot redhat dot com
- Date: Fri, 04 May 2007 21:09:30 -0400
- Subject: Re: [RFC][PATCH 2/2] uprobes: single-step out of line
On Friday, 20-Apr-2007 at 15:09 PDT, Jim Keniston wrote:
> This patch enhances uprobes to use "single-stepping out of line"
> (SSOL) to avoid probe misses in multithreaded applications. SSOL also
> reduces probe overhead by 25-30%.
Hi, Jim. I just had one question about this (mainly because I'm not
able to work through all the nitty gritty details of the patch).
Is there a way to avoid adding the "uprobe_ssol_area" struct into the
"mm_struct"? If so, the uprobes module could be easily back-ported to
kABI-frozen distros of the Linux kernel. If the "mm_struct" ends up
getting changed, that changes the "task_struct" layout, thus breaking
binary compatibility with 3rd-party kernel modules. (We're not allowed
to do this in RHEL distros.)
Cheers. -ernie