> On 14 Mar 2019, at 07.17, Marcin Dziegielewski <marcin.dziegielewski@xxxxxxxxx> wrote:
>
> In some cases write thread migration between cpus can cause
> sending writes in improper order and in consequence a lot of
> errors from device.
>
> Write thread affinity to particular cpu prevent before it.
>
> Signed-off-by: Marcin Dziegielewski <marcin.dziegielewski@xxxxxxxxx>
> ---
> drivers/lightnvm/pblk-init.c | 30 +++++++++++++++++++++++++++++-
> drivers/lightnvm/pblk.h | 1 +
> drivers/nvme/host/lightnvm.c | 1 +
> include/linux/lightnvm.h | 2 ++
> 4 files changed, 33 insertions(+), 1 deletion(-)
>
> diff --git a/drivers/lightnvm/pblk-init.c b/drivers/lightnvm/pblk-init.c
> index 81e8ed4..bd25004 100644
> --- a/drivers/lightnvm/pblk-init.c
> +++ b/drivers/lightnvm/pblk-init.c
> @@ -21,6 +21,8 @@
>
> #include "pblk.h"
> #include "pblk-trace.h"
> +#include <linux/cpumask.h>
> +#include <linux/numa.h>
>
> static unsigned int write_buffer_size;
>
> @@ -47,6 +49,8 @@ struct pblk_global_caches {
>
> struct bio_set pblk_bio_set;
>
> +cpumask_t free_cpumask;
> +
> static int pblk_rw_io(struct request_queue *q, struct pblk *pblk,
> struct bio *bio)
> {
> @@ -1098,6 +1102,9 @@ static int pblk_lines_init(struct pblk *pblk)
>
> static int pblk_writer_init(struct pblk *pblk)
> {
> + cpumask_t tmp_cpumask, cpumask;
> + int cpu;
> +
> pblk->writer_ts = kthread_create(pblk_write_ts, pblk, "pblk-writer-t");
> if (IS_ERR(pblk->writer_ts)) {
> int err = PTR_ERR(pblk->writer_ts);
> @@ -1108,6 +1115,22 @@ static int pblk_writer_init(struct pblk *pblk)
> return err;
> }
>
> + cpumask_and(&tmp_cpumask, cpumask_of_node(pblk->dev->parent->node),
> + cpu_online_mask);
> + cpumask_and(&cpumask, &tmp_cpumask, &free_cpumask);
> +
> + if (!cpumask_weight(&free_cpumask)) {
> + free_cpumask = CPU_MASK_ALL;
> + cpumask_and(&cpumask, &tmp_cpumask, &free_cpumask);
> + }
> +
> + cpu = cpumask_last(&cpumask);
> +
> + kthread_bind(pblk->writer_ts, cpu);
> +
> + cpumask_clear_cpu(cpu, &free_cpumask);
> + pblk->writer_cpu = cpu;
> +
> timer_setup(&pblk->wtimer, pblk_write_timer_fn, 0);
> mod_timer(&pblk->wtimer, jiffies + msecs_to_jiffies(100));
>
> @@ -1126,8 +1149,11 @@ static void pblk_writer_stop(struct pblk *pblk)
> "Stopping not fully synced write buffer\n");
>
> del_timer_sync(&pblk->wtimer);
> - if (pblk->writer_ts)
> + if (pblk->writer_ts) {
> + set_cpus_allowed_ptr(pblk->writer_ts, cpu_online_mask);
> kthread_stop(pblk->writer_ts);
> + cpumask_set_cpu(pblk->writer_cpu, &free_cpumask);
> + }
> }
>
> static void pblk_free(struct pblk *pblk)
> @@ -1328,6 +1354,8 @@ static int __init pblk_module_init(void)
> {
> int ret;
>
> + free_cpumask = CPU_MASK_ALL;
> +
> ret = bioset_init(&pblk_bio_set, BIO_POOL_SIZE, 0, 0);
> if (ret)
> return ret;
> diff --git a/drivers/lightnvm/pblk.h b/drivers/lightnvm/pblk.h
> index 381f074..650f983 100644
> --- a/drivers/lightnvm/pblk.h
> +++ b/drivers/lightnvm/pblk.h
> @@ -690,6 +690,7 @@ struct pblk {
> atomic_t inflight_io; /* General inflight I/O counter */
>
> struct task_struct *writer_ts;
> + int writer_cpu;
>
> /* Simple translation map of logical addresses to physical addresses.
> * The logical addresses is known by the host system, while the physical
> diff --git a/drivers/nvme/host/lightnvm.c b/drivers/nvme/host/lightnvm.c
> index 949e29e..971a19f 100644
> --- a/drivers/nvme/host/lightnvm.c
> +++ b/drivers/nvme/host/lightnvm.c
> @@ -982,6 +982,7 @@ int nvme_nvm_register(struct nvme_ns *ns, char *disk_name, int node)
> memcpy(dev->name, disk_name, DISK_NAME_LEN);
> dev->ops = &nvme_nvm_dev_ops;
> dev->private_data = ns;
> + dev->node = node;
> ns->ndev = dev;
>
> return nvm_register(dev);
> diff --git a/include/linux/lightnvm.h b/include/linux/lightnvm.h
> index 5d865a5..312029e 100644
> --- a/include/linux/lightnvm.h
> +++ b/include/linux/lightnvm.h
> @@ -427,6 +427,8 @@ struct nvm_dev {
> char name[DISK_NAME_LEN];
> void *private_data;
>
> + int node;
> +
> void *rmap;
>
> struct mutex mlock;
> --
> 1.8.3.1
We have a per-CPU semaphore that only allows to send a single I/O in
order to prevent write pointer violations. Are you seeing this error, or
is it theoretical?
Javier
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