linux-kernel - Re: [PATCH 1/4] sched,time: remove non-power-of-two divides from __acct_update

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Date:	Mon, 1 Feb 2016 09:37:00 +0100 (CET)
From:	Thomas Gleixner <tglx@...utronix.de>
To:	riel@...hat.com
cc:	linux-kernel@...r.kernel.org, fweisbec@...il.com, mingo@...nel.org,
	luto@...capital.net, peterz@...radead.org, clark@...hat.com
Subject: Re: [PATCH 1/4] sched,time: remove non-power-of-two divides from
 __acct_update_integrals

On Sun, 31 Jan 2016, riel@...hat.com wrote:
> @@ -93,9 +93,9 @@ void xacct_add_tsk(struct taskstats *stats, struct task_struct *p)
>  {
>  	struct mm_struct *mm;
>  
> -	/* convert pages-usec to Mbyte-usec */
> -	stats->coremem = p->acct_rss_mem1 * PAGE_SIZE / MB;
> -	stats->virtmem = p->acct_vm_mem1 * PAGE_SIZE / MB;
> +	/* convert pages-nsec/1024 to Mbyte-usec, see __acct_update_integrals */
> +	stats->coremem = p->acct_rss_mem1 * PAGE_SIZE / (1000 * KB);
> +	stats->virtmem = p->acct_vm_mem1 * PAGE_SIZE / (1000 * KB);

You replace "/ (1024 * 1024)" by "/ (1000 * 1024). So that's introducing a non
power of 2 division instead of removing one and wont compile on systems which
do not have a 64/32 division in hardware.

Thanks,

	tglx