From: "Frank Ch. Eigler" <fche@redhat.com>
To: Scott Dattalo <scott@dattalo.com>
Cc: sid@sources.redhat.com
Subject: Re: Profiling: --insn-count=1
Date: Thu, 01 Aug 2002 08:32:00 -0000 [thread overview]
Message-ID: <20020801113202.C16668@redhat.com> (raw)
In-Reply-To: <Pine.LNX.4.44.0208010434180.18325-100000@ruckus.brouhaha.com>; from scott@dattalo.com on Thu, Aug 01, 2002 at 05:03:55AM -0700
[-- Attachment #1: Type: text/plain, Size: 2207 bytes --]
Hi -
On Thu, Aug 01, 2002 at 05:03:55AM -0700, Scott Dattalo wrote:
> [...]
> Yeah, I suspected as much... If I had time to look into it, I'd try to add
> that feature. The way I'd approach it is I'd partition the time it takes
> an instruction to execute into two parts: the fixed amount of time the CPU
> requires and the (possibly) variable amount that the memory accesses
> require.
> The fixed portion may be ascertained when the target program is
> first loaded.
This computation is hard, totally target-dependent. See for example
the amount of work needed in gcc to model a CPU pipeline in detail
(especially the more-precise DFA models).
> The variable portion may too, depending on the address
> accessed. [...]
SID already does this part. You can configure memory modules, mappers,
caches, and a few other bits as having latency counts associated with
operations. The CPU accumulates these as penalties, combines them with
a raw instruction count, and tells the target-time scheduler the sum.
So simulated target time already includes the effect of these parameters.
> [...]
> The development scenario has thus been:
>
> 1) make optimizations to the code and test on a Linux box
> 2) debug and go back to step 1 about 100 hundred times or so.
> 3) Once convinced that an optimization has been correctly made
> re-target the makefile for an ARM processor
> 4) simulate the code (using sid as the simulator engine, of course)
> 5) analyze the simulation results
(You may also opt to have both linux & arm builds go in parallel, and
cross-check results for consistency.)
> So far, I've been satisfied knowing the total number of executed
> instructions. Objective results are easily quantified. However, I'm now
> rapidly approaching the point where the optimizations have been completed.
> While I know the approximate number of instructions, I still do not know
> the total number of CPU cycles (and hence the total time).
> [...]
To get the most precise answer, you'd best use hardware running a
profiling-capable OS. If accounting for approximate memory latencies
is good enough, then SID can be of help.
- FChE
[-- Attachment #2: Type: application/pgp-signature, Size: 232 bytes --]
next prev parent reply other threads:[~2002-08-01 15:32 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-07-31 12:53 Scott Dattalo
2002-08-01 4:18 ` Frank Ch. Eigler
2002-08-01 5:03 ` Scott Dattalo
2002-08-01 8:32 ` Frank Ch. Eigler [this message]
2002-08-01 9:00 ` Scott Dattalo
Reply instructions:
You may reply publicly to this message via plain-text email
using any one of the following methods:
* Save the following mbox file, import it into your mail client,
and reply-to-all from there: mbox
Avoid top-posting and favor interleaved quoting:
https://en.wikipedia.org/wiki/Posting_style#Interleaved_style
* Reply using the --to, --cc, and --in-reply-to
switches of git-send-email(1):
git send-email \
--in-reply-to=20020801113202.C16668@redhat.com \
--to=fche@redhat.com \
--cc=scott@dattalo.com \
--cc=sid@sources.redhat.com \
/path/to/YOUR_REPLY
https://kernel.org/pub/software/scm/git/docs/git-send-email.html
* If your mail client supports setting the In-Reply-To header
via mailto: links, try the mailto: link
Be sure your reply has a Subject: header at the top and a blank line
before the message body.
This is a public inbox, see mirroring instructions
for how to clone and mirror all data and code used for this inbox;
as well as URLs for read-only IMAP folder(s) and NNTP newsgroup(s).