linux-kernel - Re: [patch 4/4] ipc: sem optimise simple operations

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Date:	Fri, 14 Aug 2009 20:48:07 +0200
From:	Manfred Spraul <manfred@...orfullife.com>
To:	npiggin@...e.de
CC:	Andrew Morton <akpm@...ux-foundation.org>,
	Nadia Derbey <Nadia.Derbey@...l.net>,
	Pierre Peiffer <peifferp@...il.com>,
	linux-kernel@...r.kernel.org
Subject: Re: [patch 4/4] ipc: sem optimise simple operations

On 08/11/2009 01:09 PM, npiggin@...e.de wrote:
> @@ -438,23 +448,94 @@ again:
>   			continue;
>
>   		list_del(&q->list);
> +		if (q->nsops == 1)
> +			list_del(&q->simple_list);
> +		else
> +			sma->complex_count--;
> +
> +		alter = q->alter;
> +		wake_up_sem_queue(q, error);
>    
Unlink approach one: list_del() only if q->nsops!=1.

@@ -532,6 +613,9 @@ static void freeary(struct ipc_namespace
>   	/* Wake up all pending processes and let them fail with EIDRM. */
>   	list_for_each_entry_safe(q, tq,&sma->sem_pending, list) {
>   		list_del(&q->list);
> +		list_del(&q->simple_list);
> +		if (q->nsops>  1)
> +			sma->complex_count--;
>    
Unlink approach two: list_del() even if q->nsops==1.
[i.e.: rely on list_del() on an empty list is permitted].

I would merge that into a helper function.

--
     Manfred
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