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Message-ID: <2306cc76-8110-2d55-be7e-0617bfc0d316@mellanox.com>
Date: Sun, 12 May 2019 08:37:35 +0000
From: Aya Levin <ayal@...lanox.com>
To: Jiri Pirko <jiri@...nulli.us>
CC: "netdev@...r.kernel.org" <netdev@...r.kernel.org>,
Eran Ben Elisha <eranbe@...lanox.com>,
Saeed Mahameed <saeedm@...lanox.com>,
Jiri Pirko <jiri@...lanox.com>
Subject: Re: [PATCH net-next RFC] Dump SW SQ context as part of tx reporter
On 5/9/2019 11:23 AM, Jiri Pirko wrote:
> Tue, May 07, 2019 at 02:58:32PM CEST, ayal@...lanox.com wrote:
>>
>>
>> On 5/7/2019 3:41 PM, Jiri Pirko wrote:
>>> Mon, Apr 29, 2019 at 04:17:39PM CEST, ayal@...lanox.com wrote:
>>>> TX reporter reports an error on two scenarios:
>>>> - TX timeout on a specific tx queue
>>>> - TX completion error on a specific send queue
>>>> Prior to this patch, no dump data was supported by the tx reporter. This
>>>> patch adds support for SW data dump of the related SQ context. The dump
>>>> is simply the SQ's raw memory snapshot taken right after the error was
>>>> reported, before any recovery procedure was launched. With this
>>>> approach, no maintenance is needed as the driver fetch the actual data
>>>> according to the layout on which the SQ was compiled with. By providing
>>>> a SW context, one can easily debug error on a given SQ.
>>>>
>>>> In order to offline translate the raw memory into a human readable
>>>> format, the user can use some out-of-kernel scripts which receives as an
>>>> input the following:
>>>> - Object raw memory
>>>> - Driver object compiled with debug info (can be taken/generated at any time from the machine)
>>>> - Object name
>>>>
>>>> An example of such script output can be seen below.
>>>> Note: the script is not offered as part of this patch as it do not
>>>> belong to the kernel, I just described it in order to grasp the general
>>>> idea of how/what can be fetched from SW dump via devlink health.
>>>>
>>>> The output of the SW dump can be extracted by devlink health command:
>>>> $ sudo devlink health dump show pci/0000:00:0b.0 reporter tx.
>>>> mlx5e_txqsq: sqn: 6336
>>>> memory:
>>>> 00 00 00 00 00 00 00 00
>>>> 01 00 00 00 00 00 00 00
>>>> 00 00 00 00 00 00 00 00
>>>> 45 f4 88 cb 09 00 00 00
>>>> 00 00 00 00 00 00 00 00
>>>> 00 00 00 00 00 00 00 00
>>>> c0 ff ff ff 1f 00 00 00
>>>> f8 18 1e 89 81 88 ff ff
>>>> ...
>>>>
>>>> script output below, with struct members names and actual values:
>>>>
>>>> struct mlx5e_txqsq {
>>>> short unsigned int cc 0x5 ;
>>>> unsigned int dma_fifo_cc 0x5 ;
>>>> struct net_dim {
>>>> unsigned char state 0x1 ;
>>>> struct net_dim_stats {
>>>> int ppms 0x0 ;
>>>> int bpms 0x0 ;
>>>> int epms 0x0 ;
>>>> } prev_stats;
>>>> struct net_dim_sample {
>>>> long long int time 0x90766ef9d ;
>>>> unsigned int pkt_ctr 0x0 ;
>>>> unsigned int byte_ctr 0x0 ;
>>>> short unsigned int event_ctr 0x0 ;
>>>> } start_sample;
>>>> struct work_struct {
>>>> struct {
>>>> long int counter 0x1fffffffc0 ;
>>>> } data;
>>>> struct list_head {
>>>> struct list_head * next 0xffff8881b08998f8 ;
>>>> struct list_head * prev 0xffff8881b08998f8 ;
>>>> } entry;
>>>> void (*func)(struct work_struct *) 0xffffffffa02d0e30 ;
>>>> } work;
>>>> unsigned char profile_ix 0x60 ;
>>>> unsigned char mode 0x72 ;
>>>> unsigned char tune_state 0x35 ;
>>>> unsigned char steps_right 0xa0 ;
>>>> unsigned char steps_left 0xff ;
>>>> unsigned char tired 0xff ;
>>>> } dim;
>>>> short unsigned int pc 0x0 ;
>>>> unsigned int dma_fifo_pc 0x0 ;
>>>> struct mlx5e_cq {
>>>> struct mlx5_cqwq {
>>>> struct mlx5_frag_buf_ctrl {
>>>> struct mlx5_buf_list * frags 0x500000005 ;
>>>> unsigned int sz_m1 0x0 ;
>>>> short unsigned int frag_sz_m1 0x0 ;
>>>> short unsigned int strides_offset 0x0 ;
>>>> unsigned char log_sz 0x0 ;
>>>> unsigned char log_stride 0x0 ;
>>>> unsigned char log_frag_strides 0x0 ;
>>>> } fbc;
>>>> __be32 * db 0x0 ;
>>>> unsigned int cc 0x0 ;
>>>> } wq;
>>>> short unsigned int event_ctr 0x0 ;
>>>> struct napi_struct * napi 0x0 ;
>>>> struct mlx5_core_cq {
>>>> unsigned int cqn 0x0 ;
>>>> int cqe_sz 0x0 ;
>>>> __be32 * set_ci_db 0xffff8881b1aa4988 ;
>>>> __be32 * arm_db 0x3f000003ff ;
>>>> struct mlx5_uars_page * uar 0x6060a ;
>>>> struct refcount_struct {
>>>> struct {
>>>> int counter 0xa1814500 ;
>>>> } refs;
>>>> } refcount;
>>>> struct completion {
>>>> unsigned int done 0x5 ;
>>>> struct wait_queue_head {
>>>> struct spinlock {
>>>> union {
>>>> struct raw_spinlock {
>>>> struct qspinlock {
>>>> union {
>>>> struct {
>>>> int counter 0x5 ;
>>>> } val;
>>>> struct {
>>>> unsigned char locked 0x5 ;
>>>> unsigned char pending 0x0 ;
>>>> } ;
>>>> struct {
>>>> short unsigned int locked_pending 0x5 ;
>>>> short unsigned int tail 0x0 ;
>>>> } ;
>>>> } ;
>>>> } raw_lock;
>>>> } rlock;
>>>> } ;
>>>> } lock;
>>>> struct list_head {
>>>> struct list_head * next 0xffff8881b089bb88 ;
>>>> struct list_head * prev 0x4000000c0a ;
>>>> } head;
>>>> } wait;
>>>> } free;
>>>> unsigned int vector 0xa1814500 ;
>>>> unsigned int irqn 0xffff8881 ;
>>>> void (*comp)(struct mlx5_core_cq *) 0xffff8881a1814504 ;
>>>> void (*event)(struct mlx5_core_cq *, enum mlx5_event) 0xffff8881a2cdea08 ;
>>>> unsigned int cons_index 0x1 ;
>>>> unsigned int arm_sn 0x0 ;
>>>> struct mlx5_rsc_debug * dbg 0x0 ;
>>>> int pid 0x0 ;
>>>> struct {
>>>> struct list_head {
>>>> struct list_head * next 0xffffffff ;
>>>> struct list_head * prev 0xffffffffffffffff ;
>>>> } list;
>>>> void (*comp)(struct mlx5_core_cq *) 0xffffffffa0356940 ;
>>>> void * priv 0x0 ;
>>>> } tasklet_ctx;
>>>> int reset_notify_added 0x0 ;
>>>> struct list_head {
>>>> struct list_head * next 0xffffffffa0300700 ;
>>>> struct list_head * prev 0xd ;
>>>> } reset_notify;
>>>> struct mlx5_eq_comp * eq 0x0 ;
>>>> short unsigned int uid 0x9a70 ;
>>>> } mcq;
>>>> struct mlx5e_channel * channel 0xffff8881b0899a70 ;
>>>> struct mlx5_core_dev * mdev 0x4800000001 ;
>>>> struct mlx5_wq_ctrl {
>>>> struct mlx5_core_dev * mdev 0xffffffffa02d5350 ;
>>>> struct mlx5_frag_buf {
>>>> struct mlx5_buf_list * frags 0xffffffffa02d5460 ;
>>>> int npages 0x0 ;
>>>> int size 0x5 ;
>>>> unsigned char page_shift 0x8 ;
>>>> } buf;
>>>> struct mlx5_db {
>>>> __be32 * db 0x1c6 ;
>>>> union {
>>>> struct mlx5_db_pgdir * pgdir 0x0 ;
>>>> struct mlx5_ib_user_db_page * user_page 0x0 ;
>>>> } u;
>>>> long long unsigned int dma 0xffff8881b0899ab0 ;
>>>> int index 0x0 ;
>>>> } db;
>>>> } wq_ctrl;
>>>> } cq;
>>>> struct mlx5_wq_cyc {
>>>> struct mlx5_frag_buf_ctrl {
>>>> struct mlx5_buf_list * frags 0xffff8881a7600160 ;
>>>> unsigned int sz_m1 0xa7600160 ;
>>>> short unsigned int frag_sz_m1 0x8881 ;
>>>> short unsigned int strides_offset 0xffff ;
>>>> unsigned char log_sz 0x88 ;
>>>> unsigned char log_stride 0x49 ;
>>>> unsigned char log_frag_strides 0xaa ;
>>>> } fbc;
>>>> __be32 * db 0x1000000000010 ;
>>>> short unsigned int sz 0xc ;
>>>> short unsigned int wqe_ctr 0x0 ;
>>>> short unsigned int cur_sz 0x0 ;
>>>> } wq;
>>>> unsigned int dma_fifo_mask 0xa1814500 ;
>>>> struct mlx5e_sq_stats * stats 0xffff8881a33a0348 ;
>>>> struct {
>>>> struct mlx5e_sq_dma * dma_fifo 0x1a1814500 ;
>>>> struct mlx5e_tx_wqe_info * wqe_info 0x14 ;
>>>> } db;
>>>> void * uar_map 0x0 ;
>>>> struct netdev_queue * txq 0x0 ;
>>>> unsigned int sqn 0x18c0 ;
>>>> unsigned char min_inline_mode 0x0 ;
>>>> struct device * pdev 0x0 ;
>>>> unsigned int mkey_be 0x0 ;
>>>> long unsigned int state 0x0 ;
>>>> struct hwtstamp_config * tstamp 0x0 ;
>>>> struct mlx5_clock * clock 0xffff8881b1aa6f88 ;
>>>> struct mlx5_wq_ctrl {
>>>> struct mlx5_core_dev * mdev 0x3f000003ff ;
>>>> struct mlx5_frag_buf {
>>>> struct mlx5_buf_list * frags 0x6060a ;
>>>> int npages 0xa1814604 ;
>>>> int size 0xffff8881 ;
>>>> unsigned char page_shift 0x0 ;
>>>> } buf;
>>>> struct mlx5_db {
>>>> __be32 * db 0xfff ;
>>>> union {
>>>> struct mlx5_db_pgdir * pgdir 0x0 ;
>>>> struct mlx5_ib_user_db_page * user_page 0x0 ;
>>>> } u;
>>>> long long unsigned int dma 0xffff888188440000 ;
>>>> int index 0x8b074000 ;
>>>> } db;
>>>> } wq_ctrl;
>>>> struct mlx5e_channel * channel 0xffffc9000010d800 ;
>>>> int txq_ix 0xa0020180 ;
>>>> unsigned int rate_limit 0xffff8881 ;
>>>> struct work_struct {
>>>> struct {
>>>> long int counter 0x1000018c0 ;
>>>> } data;
>>>> struct list_head {
>>>> struct list_head * next 0xffff8881c32b68e8 ;
>>>> struct list_head * prev 0x800 ;
>>>> } entry;
>>>> void (*func)(struct work_struct *) 0x9 ;
>>>> } recover_work;
>>>> } ;
>>>
>>> I don't get it. You are dumping live kernel memory? There are already
>>> facilities to do that in place. Why to replicate it?
>> I am dumping the driver's memory under a lock so I can ensure it's
>> consistency (as appose to /dev/mem)
>> vmcore cannot be taken from a live kernel (without crashing).
>> I need the memory's snapshot right after the error from the driver's
>> context.
>
> Got it. However, this sounds like a generic problem not specific to
> nic drivers. How other subsystems resolve this (if they do at all)?
>
>
Correct, this is a suggested debugging solution for a generic problem:
enabling the user of a run time memory snapshot for kernel modules (at a
given error event). My research shows that other subsystems deal with
errors either by panicking (too much) or by debug/log prints (too little).
This solution is (a) low in maintenance (b) consistent in memory (c) has
small performance impact (d) use an existing infra-structure between the
kernel module and the user space.
It might be ported to other subsystems using their own user-space vs.
kernel tools. Regardless of how the memory output was generated to the
user, the parsing script can work on it.
>
>> Which other tools do you mean?
>>>
>>>
>>>>
>>>> Signed-off-by: Aya Levin <ayal@...lanox.com>
>>>> ---
>>>> .../ethernet/mellanox/mlx5/core/en/reporter_tx.c | 100 +++++++++++++++++++++
>>>> 1 file changed, 100 insertions(+)
>>>>
>>>> diff --git a/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c b/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
>>>> index 476dd97f7f2f..8a39f5525e57 100644
>>>> --- a/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
>>>> +++ b/drivers/net/ethernet/mellanox/mlx5/core/en/reporter_tx.c
>>>> @@ -9,6 +9,7 @@
>>>>
>>>> struct mlx5e_tx_err_ctx {
>>>> int (*recover)(struct mlx5e_txqsq *sq);
>>>> + int (*dump)(struct mlx5e_txqsq *sq);
>>>> struct mlx5e_txqsq *sq;
>>>> };
>>>>
>>>> @@ -281,10 +282,109 @@ static int mlx5e_tx_reporter_diagnose(struct devlink_health_reporter *reporter,
>>>> return err;
>>>> }
>>>>
>>>> +static int mlx5e_tx_reporter_sw_dump_from_ctx(struct mlx5e_priv *priv,
>>>> + struct mlx5e_txqsq *sq,
>>>> + struct devlink_fmsg *fmsg)
>>>> +{
>>>> + u64 *ptr = (u64 *)sq;
>>>> + int copy, err;
>>>> + int i = 0;
>>>> +
>>>> + if (!test_bit(MLX5E_STATE_OPENED, &priv->state))
>>>> + return 0;
>>>> +
>>>> + err = devlink_fmsg_pair_nest_start(fmsg, "mlx5e_txqsq");
>>>> + if (err)
>>>> + return err;
>>>> +
>>>> + err = devlink_fmsg_obj_nest_start(fmsg);
>>>> + if (err)
>>>> + return err;
>>>> +
>>>> + err = devlink_fmsg_arr_pair_nest_start(fmsg, "memory");
>>>> + if (err)
>>>> + return err;
>>>> +
>>>> + while (i < sizeof(struct mlx5e_txqsq)) {
>>>> + copy = sizeof(u64);
>>>> +
>>>> + if (i + copy > sizeof(struct mlx5e_txqsq))
>>>> + copy = sizeof(struct mlx5e_txqsq) - i;
>>>> +
>>>> + err = devlink_fmsg_binary_put(fmsg, ptr, copy);
>>>> + if (err)
>>>> + return err;
>>>> + ptr++;
>>>> + i += copy;
>>>> + }
>>>> +
>>>> + err = devlink_fmsg_arr_pair_nest_end(fmsg);
>>>> + if (err)
>>>> + return err;
>>>> +
>>>> + err = devlink_fmsg_obj_nest_end(fmsg);
>>>> + if (err)
>>>> + return err;
>>>> +
>>>> + err = devlink_fmsg_pair_nest_end(fmsg);
>>>> +
>>>> + return err;
>>>> +}
>>>> +
>>>> +static int mlx5e_tx_reporter_sw_dump_all(struct mlx5e_priv *priv,
>>>> + struct devlink_fmsg *fmsg)
>>>> +{
>>>> + int i, err = 0;
>>>> +
>>>> + mutex_lock(&priv->state_lock);
>>>> +
>>>> + if (!test_bit(MLX5E_STATE_OPENED, &priv->state))
>>>> + goto unlock;
>>>> +
>>>> + err = devlink_fmsg_arr_pair_nest_start(fmsg, "SQs");
>>>> + if (err)
>>>> + goto unlock;
>>>> +
>>>> + for (i = 0; i < priv->channels.num * priv->channels.params.num_tc;
>>>> + i++) {
>>>> + err = devlink_fmsg_obj_nest_start(fmsg);
>>>> + if (err)
>>>> + goto unlock;
>>>> +
>>>> + err = mlx5e_tx_reporter_sw_dump_from_ctx(priv, priv->txq2sq[i],
>>>> + fmsg);
>>>> + if (err)
>>>> + goto unlock;
>>>> +
>>>> + err = devlink_fmsg_pair_nest_end(fmsg);
>>>> + if (err)
>>>> + goto unlock;
>>>> + }
>>>> + err = devlink_fmsg_arr_pair_nest_end(fmsg);
>>>> + if (err)
>>>> + goto unlock;
>>>> +
>>>> +unlock:
>>>> + mutex_unlock(&priv->state_lock);
>>>> + return err;
>>>> +}
>>>> +
>>>> +static int mlx5e_tx_reporter_sw_dump(struct devlink_health_reporter *reporter,
>>>> + struct devlink_fmsg *fmsg, void *context)
>>>> +{
>>>> + struct mlx5e_priv *priv = devlink_health_reporter_priv(reporter);
>>>> + struct mlx5e_tx_err_ctx *err_ctx = context;
>>>> +
>>>> + return err_ctx ? mlx5e_tx_reporter_sw_dump_from_ctx(priv, err_ctx->sq,
>>>> + fmsg) :
>>>> + mlx5e_tx_reporter_sw_dump_all(priv, fmsg);
>>>> +}
>>>> +
>>>> static const struct devlink_health_reporter_ops mlx5_tx_reporter_ops = {
>>>> .name = "tx",
>>>> .recover = mlx5e_tx_reporter_recover,
>>>> .diagnose = mlx5e_tx_reporter_diagnose,
>>>> + .dump = mlx5e_tx_reporter_sw_dump,
>>>> };
>>>>
>>>> #define MLX5_REPORTER_TX_GRACEFUL_PERIOD 500
>>>> --
>>>> 2.14.1
>>>>
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