From patchwork Mon Aug 8 11:15:03 2016 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Paolo Valente X-Patchwork-Id: 73434 Delivered-To: patch@linaro.org Received: by 10.140.29.52 with SMTP id a49csp3159416qga; Mon, 8 Aug 2016 04:16:15 -0700 (PDT) X-Received: by 10.98.38.4 with SMTP id m4mr161258150pfm.47.1470654970866; Mon, 08 Aug 2016 04:16:10 -0700 (PDT) Return-Path: Received: from vger.kernel.org (vger.kernel.org. [209.132.180.67]) by mx.google.com with ESMTP id kg11si36577620pab.248.2016.08.08.04.16.10; Mon, 08 Aug 2016 04:16:10 -0700 (PDT) Received-SPF: pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) client-ip=209.132.180.67; Authentication-Results: mx.google.com; spf=pass (google.com: best guess record for domain of linux-kernel-owner@vger.kernel.org designates 209.132.180.67 as permitted sender) smtp.mailfrom=linux-kernel-owner@vger.kernel.org; dmarc=fail (p=NONE dis=NONE) header.from=linaro.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752355AbcHHLQI (ORCPT + 27 others); Mon, 8 Aug 2016 07:16:08 -0400 Received: from smtp26.sms.unimo.it ([155.185.44.26]:60054 "EHLO smtp26.sms.unimo.it" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752301AbcHHLQC (ORCPT ); Mon, 8 Aug 2016 07:16:02 -0400 Received: from [185.14.9.10] (port=55814 helo=localhost.localdomain) by smtp26.sms.unimo.it with esmtpsa (TLS1.2:RSA_AES_128_CBC_SHA256:128) (Exim 4.80) (envelope-from ) id 1bWiXH-00051g-Cw; Mon, 08 Aug 2016 13:16:00 +0200 From: Paolo Valente To: Jens Axboe , Tejun Heo Cc: linux-block@vger.kernel.org, linux-kernel@vger.kernel.org, ulf.hansson@linaro.org, linus.walleij@linaro.org, broonie@kernel.org, Paolo Valente Subject: [PATCH V2 08/22] block, cfq: get rid of latency tunables Date: Mon, 8 Aug 2016 13:15:03 +0200 Message-Id: <1470654917-4280-9-git-send-email-paolo.valente@linaro.org> X-Mailer: git-send-email 1.9.1 In-Reply-To: <1470654917-4280-1-git-send-email-paolo.valente@linaro.org> References: <1470654917-4280-1-git-send-email-paolo.valente@linaro.org> UNIMORE-X-SA-Score: -2.9 Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org BFQ guarantees a low latency for interactive applications in a completely different way with respect to CFQ. On the other hand, in terms of interface and exactly as CFQ does, BFQ exports a boolean low_latency tunable to switch low-latency heuristics on (in BFQ, these heuristics lowers latency for interactive and soft real-time applications). Finally, differently from CFQ, BFQ has not other latency tunable. Accordingly, this commit temporarily turns all latency tunables into fake tunables, by turning the functions for reading and writing these tunables into functions that just generate warnings. The commit introducing low-latency heuristics in BFQ then restores only the boolean low_latency tunable. Signed-off-by: Paolo Valente --- block/cfq-iosched.c | 36 ++++++++++++++++++++---------------- 1 file changed, 20 insertions(+), 16 deletions(-) -- 1.9.1 diff --git a/block/cfq-iosched.c b/block/cfq-iosched.c index 329ed2b..69c7c75 100644 --- a/block/cfq-iosched.c +++ b/block/cfq-iosched.c @@ -30,7 +30,6 @@ static const u64 cfq_slice_sync = NSEC_PER_SEC / 10; static u64 cfq_slice_async = NSEC_PER_SEC / 25; static const int cfq_slice_async_rq = 2; static u64 cfq_slice_idle = NSEC_PER_SEC / 125; -static const u64 cfq_target_latency = (u64)NSEC_PER_SEC * 3/10; /* 300 ms */ static const int cfq_hist_divisor = 4; /* @@ -224,12 +223,9 @@ struct cfq_data { unsigned int cfq_back_penalty; unsigned int cfq_back_max; unsigned int cfq_slice_async_rq; - unsigned int cfq_latency; u64 cfq_fifo_expire[2]; u64 cfq_slice[2]; u64 cfq_slice_idle; - u64 cfq_group_idle; - u64 cfq_target_latency; /* * Fallback dummy cfqq for extreme OOM conditions @@ -1485,7 +1481,7 @@ static bool cfq_may_dispatch(struct cfq_data *cfqd, struct cfq_queue *cfqq) * We also ramp up the dispatch depth gradually for async IO, * based on the last sync IO we serviced */ - if (!cfq_cfqq_sync(cfqq) && cfqd->cfq_latency) { + if (!cfq_cfqq_sync(cfqq)) { u64 last_sync = ktime_get_ns() - cfqd->last_delayed_sync; unsigned int depth; @@ -2323,10 +2319,8 @@ static int cfq_init_queue(struct request_queue *q, struct elevator_type *e) cfqd->cfq_back_penalty = cfq_back_penalty; cfqd->cfq_slice[0] = cfq_slice_async; cfqd->cfq_slice[1] = cfq_slice_sync; - cfqd->cfq_target_latency = cfq_target_latency; cfqd->cfq_slice_async_rq = cfq_slice_async_rq; cfqd->cfq_slice_idle = cfq_slice_idle; - cfqd->cfq_latency = 1; cfqd->hw_tag = -1; /* * we optimistically start assuming sync ops weren't delayed in last @@ -2384,8 +2378,6 @@ SHOW_FUNCTION(cfq_slice_idle_show, cfqd->cfq_slice_idle, 1); SHOW_FUNCTION(cfq_slice_sync_show, cfqd->cfq_slice[1], 1); SHOW_FUNCTION(cfq_slice_async_show, cfqd->cfq_slice[0], 1); SHOW_FUNCTION(cfq_slice_async_rq_show, cfqd->cfq_slice_async_rq, 0); -SHOW_FUNCTION(cfq_low_latency_show, cfqd->cfq_latency, 0); -SHOW_FUNCTION(cfq_target_latency_show, cfqd->cfq_target_latency, 1); #undef SHOW_FUNCTION #define USEC_SHOW_FUNCTION(__FUNC, __VAR) \ @@ -2399,7 +2391,6 @@ static ssize_t __FUNC(struct elevator_queue *e, char *page) \ USEC_SHOW_FUNCTION(cfq_slice_idle_us_show, cfqd->cfq_slice_idle); USEC_SHOW_FUNCTION(cfq_slice_sync_us_show, cfqd->cfq_slice[1]); USEC_SHOW_FUNCTION(cfq_slice_async_us_show, cfqd->cfq_slice[0]); -USEC_SHOW_FUNCTION(cfq_target_latency_us_show, cfqd->cfq_target_latency); #undef USEC_SHOW_FUNCTION #define STORE_FUNCTION(__FUNC, __PTR, MIN, MAX, __CONV) \ @@ -2431,8 +2422,6 @@ STORE_FUNCTION(cfq_slice_sync_store, &cfqd->cfq_slice[1], 1, UINT_MAX, 1); STORE_FUNCTION(cfq_slice_async_store, &cfqd->cfq_slice[0], 1, UINT_MAX, 1); STORE_FUNCTION(cfq_slice_async_rq_store, &cfqd->cfq_slice_async_rq, 1, UINT_MAX, 0); -STORE_FUNCTION(cfq_low_latency_store, &cfqd->cfq_latency, 0, 1, 0); -STORE_FUNCTION(cfq_target_latency_store, &cfqd->cfq_target_latency, 1, UINT_MAX, 1); #undef STORE_FUNCTION #define USEC_STORE_FUNCTION(__FUNC, __PTR, MIN, MAX) \ @@ -2451,12 +2440,27 @@ static ssize_t __FUNC(struct elevator_queue *e, const char *page, size_t count) USEC_STORE_FUNCTION(cfq_slice_idle_us_store, &cfqd->cfq_slice_idle, 0, UINT_MAX); USEC_STORE_FUNCTION(cfq_slice_sync_us_store, &cfqd->cfq_slice[1], 1, UINT_MAX); USEC_STORE_FUNCTION(cfq_slice_async_us_store, &cfqd->cfq_slice[0], 1, UINT_MAX); -USEC_STORE_FUNCTION(cfq_target_latency_us_store, &cfqd->cfq_target_latency, 1, UINT_MAX); #undef USEC_STORE_FUNCTION +static ssize_t cfq_fake_lat_show(struct elevator_queue *e, char *page) +{ + pr_warn_once("CFQ I/O SCHED: tried to read removed latency tunable"); + return sprintf(page, "0\n"); +} + +static ssize_t +cfq_fake_lat_store(struct elevator_queue *e, const char *page, size_t count) +{ + pr_warn_once("CFQ I/O SCHED: tried to write removed latency tunable"); + return count; +} + #define CFQ_ATTR(name) \ __ATTR(name, S_IRUGO|S_IWUSR, cfq_##name##_show, cfq_##name##_store) +#define CFQ_FAKE_LAT_ATTR(name) \ + __ATTR(name, S_IRUGO|S_IWUSR, cfq_fake_lat_show, cfq_fake_lat_store) + static struct elv_fs_entry cfq_attrs[] = { CFQ_ATTR(quantum), CFQ_ATTR(fifo_expire_sync), @@ -2470,9 +2474,9 @@ static struct elv_fs_entry cfq_attrs[] = { CFQ_ATTR(slice_async_rq), CFQ_ATTR(slice_idle), CFQ_ATTR(slice_idle_us), - CFQ_ATTR(low_latency), - CFQ_ATTR(target_latency), - CFQ_ATTR(target_latency_us), + CFQ_FAKE_LAT_ATTR(low_latency), + CFQ_FAKE_LAT_ATTR(target_latency), + CFQ_FAKE_LAT_ATTR(target_latency_us), __ATTR_NULL };