linux-kernel - Re: [PATCH v2] tracing: Have saved_cmdlines arrays all in one allocation

lists.openwall.net		lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC
Open Source and information security mailing list archives

Hash Suite: Windows password security audit tool. GUI, reports in PDF.

[<prev] [next>] [<thread-prev] [day] [month] [year] [list]

Date: Tue, 13 Feb 2024 16:09:56 -0800
From: Tim Chen <tim.c.chen@...ux.intel.com>
To: Steven Rostedt <rostedt@...dmis.org>, LKML
 <linux-kernel@...r.kernel.org>,  Linux Trace Kernel
 <linux-trace-kernel@...r.kernel.org>
Cc: Masami Hiramatsu <mhiramat@...nel.org>, Mathieu Desnoyers
 <mathieu.desnoyers@...icios.com>, Mark Rutland <mark.rutland@....com>, 
 Vincent Donnefort <vdonnefort@...gle.com>, Sven Schnelle
 <svens@...ux.ibm.com>, Mete Durlu <meted@...ux.ibm.com>
Subject: Re: [PATCH v2] tracing: Have saved_cmdlines arrays all in one
 allocation

On Tue, 2024-02-13 at 11:52 -0500, Steven Rostedt wrote:
> From: "Steven Rostedt (Google)" <rostedt@...dmis.org>
> 
> The saved_cmdlines have three arrays for mapping PIDs to COMMs:
> 
>  - map_pid_to_cmdline[]
>  - map_cmdline_to_pid[]
>  - saved_cmdlines
> 
> The map_pid_to_cmdline[] is PID_MAX_DEFAULT in size and holds the index
> into the other arrays. The map_cmdline_to_pid[] is a mapping back to the
> full pid as it can be larger than PID_MAX_DEFAULT. And the
> saved_cmdlines[] just holds the COMMs associated to the pids.
> 
> Currently the map_pid_to_cmdline[] and saved_cmdlines[] are allocated
> together (in reality the saved_cmdlines is just in the memory of the
> rounding of the allocation of the structure as it is always allocated in
> powers of two). The map_cmdline_to_pid[] array is allocated separately.
> 
> Since the rounding to a power of two is rather large (it allows for 8000
> elements in saved_cmdlines), also include the map_cmdline_to_pid[] array.
> (This drops it to 6000 by default, which is still plenty for most use
> cases). This saves even more memory as the map_cmdline_to_pid[] array
> doesn't need to be allocated.
> 
> Link: https://lore.kernel.org/linux-trace-kernel/20240212174011.068211d9@gandalf.local.home/
> 
> Signed-off-by: Steven Rostedt (Google) <rostedt@...dmis.org>


Patch looks good to me.

Reviewd-by: Tim Chen <tim.c.chen@...ux.intel.com>

> ---
> Changes since v1: https://lore.kernel.org/linux-trace-kernel/20240212180941.379c419b@gandalf.local.home/
> 
> -- Added SAVED_CMDLINE_MAP_ELEMENT_SIZE helper macro.
>