From: Ryan Arnold <rsa@us.ibm.com>
To: Michael Ellerman <michael@ellerman.id.au>
Cc: linuxppc-dev@ozlabs.org, cbe-oss-dev@ozlabs.org
Subject: Re: [PATCH] powerpc: Make rtas console _much_ faster
Date: Thu, 20 Apr 2006 15:03:11 -0500 [thread overview]
Message-ID: <1145563391.29313.174.camel@localhost.localdomain> (raw)
In-Reply-To: <20060418185534.B1ADF679F0@ozlabs.org>
On Tue, 2006-04-18 at 20:55 +0200, Michael Ellerman wrote:
> There's already code in the hvc_console driver to make the khvcd thread do
> a "quick" loop, where it just calls yield() instead of sleeping. The only code
> that triggered that behaviour was recently removed though, which I don't
> quite understand.
I think I'm the guilty part and I removed that code because it was silly
to be pushing to the tty with a partially filled buffer when we could
pack it up full. The original intention of HVC_POLL_QUICK was for
letting the TTY grok the data read from firmware. I think I was just
worried about 'off by one' errors and did it to be safe. I didn't count
on the write frequency side-effect
The hvc_console was originally quite speedy after I added khvcd (before
it was broken apart into back-end/front-end). We should review it for
performance on all platforms again in the future.
> Still, if we set HVC_POLL_QUICK whenever the push hvc_push() doesn't push all
> characters (ie. RTAS blocks), we can get good performance out of the hvc_rtas
> backend. With this patch the "benchmark" takes ~2.8 seconds.
You might as well use HVC_POLL_QUICK to speed up the write. I put that
construct in for quick reading, not quick writing but it is a dead at
the moment. Maybe rename it HVC_WRITE_QUICK?
> I'll test this on P5 LPAR, is there anyone else that uses hvc_console?
> Thoughts?
btw, there are a lot of users of hvc_console, power4 (non-interrupt
driven), power5 (interrupt-driven), cbe simulator, and rtas console.
Is it possible to make the poll frequency platform dependent?
--
Ryan S. Arnold <rsa@us.ibm.com>
IBM Linux Technology Center
Linux on Power Toolchain
next prev parent reply other threads:[~2006-04-20 20:03 UTC|newest]
Thread overview: 6+ messages / expand[flat|nested] mbox.gz Atom feed top
2006-04-18 18:55 [PATCH] powerpc: Make rtas console _much_ faster Michael Ellerman
2006-04-18 19:30 ` Olof Johansson
2006-04-20 20:03 ` Ryan Arnold [this message]
2006-04-20 20:25 ` question on why hvc_console calls hvc_poll() in hvc_handle_interrupt() Ryan Arnold
2006-05-03 7:42 ` Michael Ellerman
-- strict thread matches above, loose matches on Subject: below --
2006-04-29 8:00 [PATCH 1/3] powerpc: Make rtas console _much_ faster Arnd Bergmann
2006-04-30 3:07 ` [PATCH] " Michael Ellerman
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