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Message-ID: <d89c3460-cacf-4df1-bc31-3b710671d699@nvidia.com>
Date: Tue, 1 Apr 2025 02:55:15 +0000
From: Chaitanya Kulkarni <chaitanyak@...dia.com>
To: Yaxiong Tian <iambestgod@...com>, "kbusch@...nel.org" <kbusch@...nel.org>,
"axboe@...nel.dk" <axboe@...nel.dk>, "hch@....de" <hch@....de>,
"sagi@...mberg.me" <sagi@...mberg.me>
CC: "linux-nvme@...ts.infradead.org" <linux-nvme@...ts.infradead.org>,
"linux-kernel@...r.kernel.org" <linux-kernel@...r.kernel.org>, Yaxiong Tian
<tianyaxiong@...inos.cn>
Subject: Re: [PATCH v2 2/3] nvme: add sysfs interface for APST table updates
On 3/27/25 18:40, Yaxiong Tian wrote:
> From: Yaxiong Tian <tianyaxiong@...inos.cn>
>
> Currently, the APST (Autonomous Power State Transition) table can only be
> updated during module initialization via module parameters or indirectly
> by setting QoS latency requirements. This patch adds a direct sysfs
> interface to allow dynamic updates to the APST table at runtime.
>
> The new sysfs entry is created at:
> /sys/class/nvme/<controller>/apst_update
>
> This provides more flexibility in power management tuning without
> requiring module reload or QoS latency changes.
>
> Example usage:
> update nvme module parameters.
> echo 1 > /sys/class/nvme/nvme0/apst_update
>
> Signed-off-by: Yaxiong Tian <tianyaxiong@...inos.cn>
by any chance can you please provide a use-case in which scenario
you need to dynamically updating APST ?
> ---
> drivers/nvme/host/core.c | 9 +++++++--
> drivers/nvme/host/nvme.h | 2 ++
> drivers/nvme/host/sysfs.c | 23 +++++++++++++++++++++++
> 3 files changed, 32 insertions(+), 2 deletions(-)
>
> diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c
> index fb0404fee551..9dea1046b8b4 100644
> --- a/drivers/nvme/host/core.c
> +++ b/drivers/nvme/host/core.c
> @@ -2654,7 +2654,7 @@ static bool nvme_apst_get_transition_time(u64 total_latency,
> *
> * Users can set ps_max_latency_us to zero to turn off APST.
> */
> -static int nvme_configure_apst(struct nvme_ctrl *ctrl)
> +int nvme_configure_apst(struct nvme_ctrl *ctrl)
> {
> struct nvme_feat_auto_pst *table;
> unsigned apste = 0;
> @@ -2778,8 +2778,11 @@ static void nvme_set_latency_tolerance(struct device *dev, s32 val)
>
> if (ctrl->ps_max_latency_us != latency) {
> ctrl->ps_max_latency_us = latency;
> - if (nvme_ctrl_state(ctrl) == NVME_CTRL_LIVE)
> + if (nvme_ctrl_state(ctrl) == NVME_CTRL_LIVE) {
> + mutex_lock(&ctrl->apst_lock);
> nvme_configure_apst(ctrl);
> + mutex_unlock(&ctrl->apst_lock);
> + }
> }
> }
>
> @@ -4852,6 +4855,8 @@ int nvme_init_ctrl(struct nvme_ctrl *ctrl, struct device *dev,
> ctrl->ka_cmd.common.opcode = nvme_admin_keep_alive;
> ctrl->ka_last_check_time = jiffies;
>
> + mutex_init(&ctrl->apst_lock);
> +
> BUILD_BUG_ON(NVME_DSM_MAX_RANGES * sizeof(struct nvme_dsm_range) >
> PAGE_SIZE);
> ctrl->discard_page = alloc_page(GFP_KERNEL);
> diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h
> index 51e078642127..7f8e10f5bf7a 100644
> --- a/drivers/nvme/host/nvme.h
> +++ b/drivers/nvme/host/nvme.h
> @@ -385,6 +385,7 @@ struct nvme_ctrl {
> key_serial_t tls_pskid;
>
> /* Power saving configuration */
> + struct mutex apst_lock;
> u64 ps_max_latency_us;
> bool apst_enabled;
>
> @@ -828,6 +829,7 @@ void nvme_unfreeze(struct nvme_ctrl *ctrl);
> void nvme_wait_freeze(struct nvme_ctrl *ctrl);
> int nvme_wait_freeze_timeout(struct nvme_ctrl *ctrl, long timeout);
> void nvme_start_freeze(struct nvme_ctrl *ctrl);
> +int nvme_configure_apst(struct nvme_ctrl *ctrl);
>
> static inline enum req_op nvme_req_op(struct nvme_command *cmd)
> {
> diff --git a/drivers/nvme/host/sysfs.c b/drivers/nvme/host/sysfs.c
> index 6d31226f7a4f..5003cb294d65 100644
> --- a/drivers/nvme/host/sysfs.c
> +++ b/drivers/nvme/host/sysfs.c
> @@ -684,6 +684,28 @@ static DEVICE_ATTR(dhchap_ctrl_secret, S_IRUGO | S_IWUSR,
> nvme_ctrl_dhchap_ctrl_secret_show, nvme_ctrl_dhchap_ctrl_secret_store);
> #endif
>
> +static ssize_t apst_update_store(struct device *dev,
> + struct device_attribute *attr,
> + const char *buf, size_t size)
> +{
> + int err;
> + bool bool_data = false;
> + struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
reverse tree ?
+ struct nvme_ctrl *ctrl = dev_get_drvdata(dev);
+ bool bool_data = false;
+ int err;
> + err = kstrtobool(buf, &bool_data);
add new line above after all the declarations ?
-ck
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