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Subject: Re: [PATCH] bfq: default slice_idle to 0 for SSD
From:   Paolo Valente <paolo.valente@linaro.org>
In-Reply-To: <20220308000253.645107-1-khazhy@google.com>
Date:   Tue, 8 Mar 2022 10:12:59 +0100
Cc:     Jens Axboe <axboe@kernel.dk>,
        linux-block <linux-block@vger.kernel.org>,
        LKML <linux-kernel@vger.kernel.org>
Content-Transfer-Encoding: quoted-printable
Message-Id: <61B4B869-1B0B-4FE9-9AEE-712A3F50EDA6@linaro.org>
References: <20220308000253.645107-1-khazhy@google.com>
To:     Khazhismel Kumykov <khazhy@google.com>
Precedence: bulk


> Il giorno 8 mar 2022, alle ore 01:02, Khazhismel Kumykov =
<khazhy@google.com> ha scritto:
>=20
> This improves performance on SSDs dramatically, and was default for =
CFQ
>=20

Ho,
unfortunately it is unacceptable, because it simply switches BFQ off =
with sync I/O.

Thanks,
Paolo

> Signed-off-by: Khazhismel Kumykov <khazhy@google.com>
> ---
> block/bfq-iosched.c | 3 ++-
> 1 file changed, 2 insertions(+), 1 deletion(-)
>=20
> diff --git a/block/bfq-iosched.c b/block/bfq-iosched.c
> index 36a66e97e3c2..f3196036940c 100644
> --- a/block/bfq-iosched.c
> +++ b/block/bfq-iosched.c
> @@ -7105,7 +7105,8 @@ static int bfq_init_queue(struct request_queue =
*q, struct elevator_type *e)
> 	bfqd->bfq_fifo_expire[1] =3D bfq_fifo_expire[1];
> 	bfqd->bfq_back_max =3D bfq_back_max;
> 	bfqd->bfq_back_penalty =3D bfq_back_penalty;
> -	bfqd->bfq_slice_idle =3D bfq_slice_idle;
> +	/* Default to no idling for SSDs */
> +	bfqd->bfq_slice_idle =3D blk_queue_nonrot(q) ? 0 : =
bfq_slice_idle;
> 	bfqd->bfq_timeout =3D bfq_timeout;
>=20
> 	bfqd->bfq_large_burst_thresh =3D 8;
> --=20
> 2.35.1.616.g0bdcbb4464-goog
>=20