Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757685AbcLOUhL (ORCPT ); Thu, 15 Dec 2016 15:37:11 -0500 Received: from mx0b-00082601.pphosted.com ([67.231.153.30]:60573 "EHLO mx0a-00082601.pphosted.com" rhost-flags-OK-OK-OK-FAIL) by vger.kernel.org with ESMTP id S1756289AbcLOUdL (ORCPT ); Thu, 15 Dec 2016 15:33:11 -0500 Smtp-Origin-Hostprefix: devbig From: Shaohua Li Smtp-Origin-Hostname: devbig638.prn2.facebook.com To: , CC: , , , Smtp-Origin-Cluster: prn2c22 Subject: [PATCH V5 14/17] blk-throttle: add interface for per-cgroup target latency Date: Thu, 15 Dec 2016 12:33:05 -0800 Message-ID: <780b07f3e3163f5fbacaa32a4eb808e3b7940f2e.1481833017.git.shli@fb.com> X-Mailer: git-send-email 2.9.3 In-Reply-To: References: X-FB-Internal: Safe MIME-Version: 1.0 Content-Type: text/plain X-Proofpoint-Spam-Reason: safe X-FB-Internal: Safe X-Proofpoint-Virus-Version: vendor=fsecure engine=2.50.10432:,, definitions=2016-12-15_14:,, signatures=0 Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 4746 Lines: 131 Here we introduce per-cgroup latency target. The target determines how a cgroup can afford latency increasement. We will use the target latency to calculate a threshold and use it to schedule IO for cgroups. If a cgroup's bandwidth is below its low limit but its average latency is below the threshold, other cgroups can safely dispatch more IO even their bandwidth is higher than their low limits. On the other hand, if the first cgroup's latency is higher than the threshold, other cgroups are throttled to their low limits. So the target latency determines how we efficiently utilize free disk resource without sacifice of worload's IO latency. For example, assume 4k IO average latency is 50us when disk isn't congested. A cgroup sets the target latency to 30us. Then the cgroup can accept 50+30=80us IO latency. If the cgroupt's average IO latency is 90us and its bandwidth is below low limit, other cgroups are throttled to their low limit. If the cgroup's average IO latency is 60us, other cgroups are allowed to dispatch more IO. When other cgroups dispatch more IO, the first cgroup's IO latency will increase. If it increases to 81us, we then throttle other cgroups. User will configure the interface in this way: echo "8:16 rbps=2097152 wbps=max latency=100 idle=200" > io.low latency is in microsecond unit Signed-off-by: Shaohua Li --- block/blk-throttle.c | 30 ++++++++++++++++++++++++++---- 1 file changed, 26 insertions(+), 4 deletions(-) diff --git a/block/blk-throttle.c b/block/blk-throttle.c index 62fe72ea..3431b1d 100644 --- a/block/blk-throttle.c +++ b/block/blk-throttle.c @@ -151,6 +151,7 @@ struct throtl_grp { unsigned long last_check_time; + u64 latency_target; /* When did we start a new slice */ unsigned long slice_start[2]; unsigned long slice_end[2]; @@ -438,6 +439,11 @@ static struct blkg_policy_data *throtl_pd_alloc(gfp_t gfp, int node) } tg->idle_ttime_threshold = U64_MAX; + /* + * target latency default 0, eg, latency threshold is 0, which means + * cgroup's latency is always higher than threshold + */ + return &tg->pd; } @@ -1426,6 +1432,7 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd, const char *dname = blkg_dev_name(pd->blkg); char bufs[4][21] = { "max", "max", "max", "max" }; char idle_time[26] = ""; + char latency_time[26] = ""; if (!dname) return 0; @@ -1434,8 +1441,9 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd, tg->bps_conf[WRITE][off] == U64_MAX && tg->iops_conf[READ][off] == UINT_MAX && tg->iops_conf[WRITE][off] == UINT_MAX && - (off != LIMIT_LOW || tg->idle_ttime_threshold == - tg->td->dft_idle_ttime_threshold)) + (off != LIMIT_LOW || + (tg->idle_ttime_threshold == tg->td->dft_idle_ttime_threshold && + tg->latency_target == 0))) return 0; if (tg->bps_conf[READ][off] != U64_MAX) @@ -1456,10 +1464,18 @@ static u64 tg_prfill_limit(struct seq_file *sf, struct blkg_policy_data *pd, else snprintf(idle_time, sizeof(idle_time), " idle=%llu", div_u64(tg->idle_ttime_threshold, 1000)); + + if (tg->latency_target == U64_MAX) + strcpy(latency_time, " latency=max"); + else + snprintf(latency_time, sizeof(latency_time), + " latency=%llu", + div_u64(tg->latency_target, 1000)); } - seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s\n", - dname, bufs[0], bufs[1], bufs[2], bufs[3], idle_time); + seq_printf(sf, "%s rbps=%s wbps=%s riops=%s wiops=%s%s%s\n", + dname, bufs[0], bufs[1], bufs[2], bufs[3], idle_time, + latency_time); return 0; } @@ -1478,6 +1494,7 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of, struct throtl_grp *tg; u64 v[4]; u64 idle_time; + u64 latency_time; int ret; int index = of_cft(of)->private; @@ -1493,6 +1510,7 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of, v[3] = tg->iops_conf[WRITE][index]; idle_time = tg->idle_ttime_threshold; + latency_time = tg->latency_target; while (true) { char tok[27]; /* wiops=18446744073709551616 */ char *p; @@ -1526,6 +1544,8 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of, v[3] = min_t(u64, val, UINT_MAX); else if (off == LIMIT_LOW && !strcmp(tok, "idle")) idle_time = val; + else if (off == LIMIT_LOW && !strcmp(tok, "latency")) + latency_time = val; else goto out_finish; } @@ -1556,6 +1576,8 @@ static ssize_t tg_set_limit(struct kernfs_open_file *of, tg->td->limit_index = LIMIT_LOW; tg->idle_ttime_threshold = (idle_time == U64_MAX) ? U64_MAX : idle_time * 1000; + tg->latency_target = (latency_time == U64_MAX) ? + U64_MAX : latency_time * 1000; } tg_conf_updated(tg); ret = 0; -- 2.9.3