Date: Sun, 28 Mar 2004 18:53:47 +0200
Message-ID: <s5hwu549alg.wl@alsa2.suse.de>
From: Takashi Iwai <tiwai@suse.de>
To: dipankar@in.ibm.com
Cc: "Paul E. McKenney" <paulmck@us.ibm.com>,
       Arjan van de Ven <arjanv@redhat.com>, Robert Love <rml@ximian.com>,
       Andrew Morton <akpm@osdl.org>, linux-kernel@vger.kernel.org
Subject: Re: [PATCH] RCU for low latency (experimental)
In-Reply-To: <20040324234643.GD12035@in.ibm.com>
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At Thu, 25 Mar 2004 05:16:43 +0530,
Dipankar Sarma wrote:
> 
> On Thu, Mar 25, 2004 at 12:34:30AM +0100, Andrea Arcangeli wrote:
> > On Thu, Mar 25, 2004 at 04:41:45AM +0530, Dipankar Sarma wrote:
> > > That was not 16 callbacks per tick, it was 16 callbacks in one
> > > batch of a single softirq. And then I reschedule the RCU tasklet
> > 
> > sorry so you're already using tasklets in current code? I misunderstood
> > the current code then.
> 
> +               if (count >= rcumaxbatch) {
> +                       RCU_plugticks(cpu) = rcuplugticks;
> +                       if (!RCU_plugticks(cpu))
> +                               tasklet_hi_schedule(&RCU_tasklet(cpu));
> +                       break;
> +               }

it seems count is never incremented in your patch...
or am i missing something?

anyway, i confirmed that with the original krcud patch the latency
with dcache flood can be eliminated.

for the non-preemptive case, rcu_bh_callback_limit() should return
bhlimit always, though.  otherwise cond_resched() isn't called in the
callback loop properly.


Takashi
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