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Tue, 4 Nov 2025 10:45:48 +0000 (GMT) From: Nilay Shroff To: linux-nvme@lists.infradead.org Cc: hare@suse.de, hch@lst.de, kbusch@kernel.org, sagi@grimberg.me, dwagner@suse.de, axboe@kernel.dk, gjoyce@ibm.com Subject: [RFC PATCHv4 6/6] nvme-multipath: add debugfs attribute adaptive_stat Date: Tue, 4 Nov 2025 16:15:21 +0530 Message-ID: <20251104104533.138481-7-nilay@linux.ibm.com> X-Mailer: git-send-email 2.51.0 In-Reply-To: <20251104104533.138481-1-nilay@linux.ibm.com> References: <20251104104533.138481-1-nilay@linux.ibm.com> MIME-Version: 1.0 Content-Transfer-Encoding: 8bit X-TM-AS-GCONF: 00 X-Proofpoint-GUID: TcmjDPy3kpGRRX0Ghx9hWtE0laz6Dj97 X-Authority-Analysis: v=2.4 cv=MKhtWcZl c=1 sm=1 tr=0 ts=6909d962 cx=c_pps a=5BHTudwdYE3Te8bg5FgnPg==:117 a=5BHTudwdYE3Te8bg5FgnPg==:17 a=6UeiqGixMTsA:10 a=VkNPw1HP01LnGYTKEx00:22 a=VnNF1IyMAAAA:8 a=GMZBDc3o4BUkPsUqmQYA:9 a=cPQSjfK2_nFv0Q5t_7PE:22 X-Proofpoint-ORIG-GUID: TcmjDPy3kpGRRX0Ghx9hWtE0laz6Dj97 X-Proofpoint-Spam-Details-Enc: AW1haW4tMjUxMTAxMDAwMSBTYWx0ZWRfX1AYdE0/cIKms MMVSdnLapgU4cszSNMcKICqFm0o/BUgBstKrygaj6/j387iGEZAelw820GaNgxPAH/9PVtv0gR0 VuJ7Be/GmRHHOlXyHDvXhVgyAx9pArjV46pJRvEIA4FPZNipWLqg3+CX0gkZptkY41aTP63bHmO 33tqR8brbjXSuD1rsgDU1UhcVji5hAf8WFMv5jLVz8GL1b3+6vUdjVibxHW4qmklXrDUOHiyrV9 nwbazHZGdVd+NQbYj+12DOG1ekyj7ieERY/cs4HgKyWHr972xVsOhBZVrUZI4eNvCbqBLUDLotj hX2CY6S0pKVoR7B0oPAbs4WfFSRteKg1bB28bENDw+S8T08pRQobbfj6pfj74BMUb26ap0wUf4s Lez7avNfZ3fS29Nimwye/tIuUhPorg== X-Proofpoint-Virus-Version: vendor=baseguard engine=ICAP:2.0.293,Aquarius:18.0.1121,Hydra:6.1.9,FMLib:17.12.100.49 definitions=2025-11-03_06,2025-11-03_03,2025-10-01_01 X-Proofpoint-Spam-Details: rule=outbound_notspam policy=outbound score=0 priorityscore=1501 suspectscore=0 bulkscore=0 impostorscore=0 clxscore=1015 lowpriorityscore=0 malwarescore=0 adultscore=0 phishscore=0 spamscore=0 classifier=typeunknown authscore=0 authtc= authcc= route=outbound adjust=0 reason=mlx scancount=1 engine=8.19.0-2510240000 definitions=main-2511010001 X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20251104_024558_270380_2BBE2D54 X-CRM114-Status: GOOD ( 18.05 ) X-BeenThere: linux-nvme@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Sender: "Linux-nvme" Errors-To: linux-nvme-bounces+linux-nvme=archiver.kernel.org@lists.infradead.org This commit introduces a new debugfs attribute, "adaptive_stat", under both per-path and head debugfs directories (defined under /sys/kernel/ debug/block/). This attribute provides visibility into the internal state of the adaptive I/O policy to aid in debugging and performance analysis. For per-path entries, "adaptive_stat" reports the corresponding path statistics such as I/O weight, selection count, processed samples, and ignored samples. For head entries, it reports per-CPU statistics for each reachable path, including I/O weight, path score, smoothed (EWMA) latency, selection count, processed samples, and ignored samples. These additions enhance observability of the adaptive I/O path selection behavior and help diagnose imbalance or instability in multipath performance. Reviewed-by: Hannes Reinecke Signed-off-by: Nilay Shroff --- drivers/nvme/host/debugfs.c | 113 ++++++++++++++++++++++++++++++++++++ 1 file changed, 113 insertions(+) diff --git a/drivers/nvme/host/debugfs.c b/drivers/nvme/host/debugfs.c index e382fa411b13..28de4a8e2333 100644 --- a/drivers/nvme/host/debugfs.c +++ b/drivers/nvme/host/debugfs.c @@ -182,6 +182,115 @@ static ssize_t nvme_adp_weight_timeout_store(void *data, WRITE_ONCE(head->adp_weight_timeout, res * NSEC_PER_SEC); return count; } + +static void *nvme_mpath_adp_stat_start(struct seq_file *m, loff_t *pos) +{ + struct nvme_ns *ns; + struct nvme_debugfs_ctx *ctx = m->private; + struct nvme_ns_head *head = ctx->data; + + /* Remember srcu index, so we can unlock later. */ + ctx->srcu_idx = srcu_read_lock(&head->srcu); + ns = list_first_or_null_rcu(&head->list, struct nvme_ns, siblings); + + while (*pos && ns) { + ns = list_next_or_null_rcu(&head->list, &ns->siblings, + struct nvme_ns, siblings); + (*pos)--; + } + + return ns; +} + +static void *nvme_mpath_adp_stat_next(struct seq_file *m, void *v, loff_t *pos) +{ + struct nvme_ns *ns = v; + struct nvme_debugfs_ctx *ctx = m->private; + struct nvme_ns_head *head = ctx->data; + + (*pos)++; + + return list_next_or_null_rcu(&head->list, &ns->siblings, + struct nvme_ns, siblings); +} + +static void nvme_mpath_adp_stat_stop(struct seq_file *m, void *v) +{ + struct nvme_debugfs_ctx *ctx = m->private; + struct nvme_ns_head *head = ctx->data; + int srcu_idx = ctx->srcu_idx; + + srcu_read_unlock(&head->srcu, srcu_idx); +} + +static int nvme_mpath_adp_stat_show(struct seq_file *m, void *v) +{ + int i, cpu; + struct nvme_path_stat *stat; + struct nvme_ns *ns = v; + + seq_printf(m, "%s:\n", ns->disk->disk_name); + for_each_online_cpu(cpu) { + seq_printf(m, "cpu %d : ", cpu); + for (i = 0; i < NVME_NUM_STAT_GROUPS; i++) { + stat = &per_cpu_ptr(ns->info, cpu)[i].stat; + seq_printf(m, "%u %u %llu %llu %llu %llu %llu ", + stat->weight, stat->credit, stat->score, + stat->slat_ns, stat->sel, + stat->nr_samples, stat->nr_ignored); + } + seq_putc(m, '\n'); + } + return 0; +} + +static const struct seq_operations nvme_mpath_adp_stat_seq_ops = { + .start = nvme_mpath_adp_stat_start, + .next = nvme_mpath_adp_stat_next, + .stop = nvme_mpath_adp_stat_stop, + .show = nvme_mpath_adp_stat_show +}; + +static void adp_stat_read_all(struct nvme_ns *ns, struct nvme_path_stat *batch) +{ + int i, cpu; + u32 ncpu[NVME_NUM_STAT_GROUPS] = {0}; + struct nvme_path_stat *stat; + + for_each_online_cpu(cpu) { + for (i = 0; i < NVME_NUM_STAT_GROUPS; i++) { + stat = &per_cpu_ptr(ns->info, cpu)[i].stat; + batch[i].sel += stat->sel; + batch[i].nr_samples += stat->nr_samples; + batch[i].nr_ignored += stat->nr_ignored; + batch[i].weight += stat->weight; + if (stat->weight) + ncpu[i]++; + } + } + + for (i = 0; i < NVME_NUM_STAT_GROUPS; i++) { + if (!ncpu[i]) + continue; + batch[i].weight = DIV_U64_ROUND_CLOSEST(batch[i].weight, + ncpu[i]); + } +} + +static int nvme_ns_adp_stat_show(void *data, struct seq_file *m) +{ + int i; + struct nvme_path_stat stat[NVME_NUM_STAT_GROUPS] = {0}; + struct nvme_ns *ns = (struct nvme_ns *)data; + + adp_stat_read_all(ns, stat); + for (i = 0; i < NVME_NUM_STAT_GROUPS; i++) { + seq_printf(m, "%u %llu %llu %llu ", + stat[i].weight, stat[i].sel, + stat[i].nr_samples, stat[i].nr_ignored); + } + return 0; +} #endif static const struct nvme_debugfs_attr nvme_mpath_debugfs_attrs[] = { @@ -190,11 +299,15 @@ static const struct nvme_debugfs_attr nvme_mpath_debugfs_attrs[] = { nvme_adp_ewma_shift_store}, {"adaptive_weight_timeout", 0600, nvme_adp_weight_timeout_show, nvme_adp_weight_timeout_store}, + {"adaptive_stat", 0400, .seq_ops = &nvme_mpath_adp_stat_seq_ops}, #endif {}, }; static const struct nvme_debugfs_attr nvme_ns_debugfs_attrs[] = { +#ifdef CONFIG_NVME_MULTIPATH + {"adaptive_stat", 0400, nvme_ns_adp_stat_show}, +#endif {}, }; -- 2.51.0