linux-kernel - Re: [PATCH v2] block: make iolatency avg

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Message-ID: <20180801154958.GP1206094@devbig004.ftw2.facebook.com>
Date:   Wed, 1 Aug 2018 08:49:58 -0700
From:   Tejun Heo <tj@...nel.org>
To:     Dennis Zhou <dennisszhou@...il.com>
Cc:     Jens Axboe <axboe@...nel.dk>, Josef Bacik <jbacik@...com>,
        kernel-team@...com, linux-block@...r.kernel.org,
        linux-kernel@...r.kernel.org, Johannes Weiner <hannes@...xchg.org>
Subject: Re: [PATCH v2] block: make iolatency avg_lat exponentially decay

Hello,

On Tue, Jul 31, 2018 at 05:25:59PM -0700, Dennis Zhou wrote:
...
> +	/*
> +	 * CALC_LOAD takes in a number stored in fixed point representation.
> +	 * Because we are using this for IO time in ns, the values stored
> +	 * are significantly larger than the FIXED_1 denominator (2048).
> +	 * Therefore, rounding errors in the calculation are negligible and
> +	 * can be ignored.
> +	 */
> +	exp_idx = min_t(int, BLKIOLATENCY_NR_EXP_FACTORS - 1,
> +			iolat->cur_win_nsec / BLKIOLATENCY_EXP_BUCKET_SIZE);

Build bot is complaining about naked 64bit div.  Should use one of the
div64*() helpers.

Looks good to me.  Once Johannes's concerns are addressed, please feel
free to add

Acked-by: Tejun Heo <tj@...nel.org>

Thanks.

-- 
tejun