From: Steven Rostedt <rostedt@goodmis.org>
To: David Laight <David.Laight@ACULAB.COM>
Cc: "linux-kernel@vger.kernel.org" <linux-kernel@vger.kernel.org>,
Ingo Molnar <mingo@kernel.org>,
Andrew Morton <akpm@linux-foundation.org>
Subject: Re: [for-next][PATCH 12/17] fgraph: Make overruns 4 bytes in graph stack structure
Date: Thu, 12 Nov 2020 09:39:15 -0500 [thread overview]
Message-ID: <20201112093915.16a42644@gandalf.local.home> (raw)
In-Reply-To: <aabe0dd1fd7b46aaaadb2b34912b6718@AcuMS.aculab.com>
On Thu, 12 Nov 2020 09:18:21 +0000
David Laight <David.Laight@ACULAB.COM> wrote:
> From: Steven Rostedt
> > Sent: 12 November 2020 00:33
> >
> > Inspecting the data structures of the function graph tracer, I found that
> > the overrun value is unsigned long, which is 8 bytes on a 64 bit machine,
> > and not only that, the depth is an int (4 bytes). The overrun can be simply
> > an unsigned int (4 bytes) and pack the ftrace_graph_ret structure better.
> >
> > The depth is moved up next to the func, as it is used more often with func,
> > and improves cache locality.
> ...
> > } __packed;
>
> Does this many any/much difference given that the structure is
> marked __packed?
>
> OTOH the __packed will (probably) kill performance on systems
> that don't support mis-aligned accesses.
>
I think you answered your own question ;-)
That was why I try to keep 4 byte items together. But the point here was
that overrun is hardly ever used (probably could just be a single byte),
and there was no reason for it to be a long.
-- Steve
next prev parent reply other threads:[~2020-11-12 14:39 UTC|newest]
Thread overview: 20+ messages / expand[flat|nested] mbox.gz Atom feed top
2020-11-12 0:32 [for-next][PATCH 00/17] tracing: Updates for 5.11 Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 01/17] ftrace: Move the recursion testing into global headers Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 02/17] ftrace: Add ftrace_test_recursion_trylock() helper function Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 03/17] ftrace: Optimize testing what context current is in Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 04/17] pstore/ftrace: Add recursion protection to the ftrace callback Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 05/17] kprobes/ftrace: " Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 06/17] livepatch/ftrace: " Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 07/17] livepatch: Trigger WARNING if livepatch function fails due to recursion Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 08/17] perf/ftrace: Add recursion protection to the ftrace callback Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 09/17] perf/ftrace: Check for rcu_is_watching() in callback function Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 10/17] ftrace: Reverse what the RECURSION flag means in the ftrace_ops Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 11/17] ftrace: Add recording of functions that caused recursion Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 12/17] fgraph: Make overruns 4 bytes in graph stack structure Steven Rostedt
2020-11-12 9:18 ` David Laight
2020-11-12 14:39 ` Steven Rostedt [this message]
2020-11-12 0:32 ` [for-next][PATCH 13/17] ftrace: Clean up the recursion code a bit Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 14/17] ring-buffer: Add recording of ring buffer recursion into recursed_functions Steven Rostedt
2020-11-12 0:32 ` [for-next][PATCH 15/17] ftrace: Remove unused varible ret Steven Rostedt
2020-11-12 0:33 ` [for-next][PATCH 16/17] tracing: Fix some typos in comments Steven Rostedt
2020-11-12 0:33 ` [for-next][PATCH 17/17] MAINTAINERS: assign ./fs/tracefs to TRACING Steven Rostedt
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