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Date: Tue, 20 Jun 2017 09:34:22 +0800
From: Xiubo Li <lixiubo@...s.chinamobile.com>
To: Mike Christie <mchristi@...hat.com>, nab@...ux-iscsi.org
Cc: agrover@...hat.com, namei.unix@...il.com, sheng@...ker.org,
linux-scsi@...r.kernel.org, target-devel@...r.kernel.org,
linux-kernel@...r.kernel.org
Subject: Re: [PATCH] tcmu: Add fifo type waiter list support to
avoidstarvation
Hi Nic & Mike
I will update this just after the issue reported by Bryant on his
environment been fixed later.
Thanks,
BRs
Xiubo
On 2017年06月04日 12:11, Mike Christie wrote:
> On 05/04/2017 09:51 PM, lixiubo@...s.chinamobile.com wrote:
>> From: Xiubo Li <lixiubo@...s.chinamobile.com>
>>
>> The fifo type waiter list will hold the udevs who are waiting for the
>> blocks from the data global pool. The unmap thread will try to feed the
>> first udevs in waiter list, if the global free blocks available are
>> not enough, it will stop traversing the list and abort waking up the
>> others.
>>
>> Signed-off-by: Xiubo Li <lixiubo@...s.chinamobile.com>
>> ---
>> drivers/target/target_core_user.c | 82 +++++++++++++++++++++++++++++++--------
>> 1 file changed, 66 insertions(+), 16 deletions(-)
>>
>> diff --git a/drivers/target/target_core_user.c b/drivers/target/target_core_user.c
>> index 9045837..10c99e7 100644
>> --- a/drivers/target/target_core_user.c
>> +++ b/drivers/target/target_core_user.c
>> @@ -97,6 +97,7 @@ struct tcmu_hba {
>>
>> struct tcmu_dev {
>> struct list_head node;
>> + struct list_head waiter;
>>
>> struct se_device se_dev;
>>
>> @@ -123,7 +124,7 @@ struct tcmu_dev {
>> wait_queue_head_t wait_cmdr;
>> struct mutex cmdr_lock;
>>
>> - bool waiting_global;
>> + uint32_t waiting_blocks;
>> uint32_t dbi_max;
>> uint32_t dbi_thresh;
>> DECLARE_BITMAP(data_bitmap, DATA_BLOCK_BITS);
>> @@ -165,6 +166,10 @@ struct tcmu_cmd {
>> static DEFINE_MUTEX(root_udev_mutex);
>> static LIST_HEAD(root_udev);
>>
>> +/* The data blocks global pool waiter list */
>> +static DEFINE_MUTEX(root_udev_waiter_mutex);
> Sorry for the delay.
>
>
> Could you just add a comment about the lock ordering. It will be helpful
> to new engineers/reviewers to check for errors.
>
>
>> +static LIST_HEAD(root_udev_waiter);
>> +
>> static atomic_t global_db_count = ATOMIC_INIT(0);
>>
>> static struct kmem_cache *tcmu_cmd_cache;
>> @@ -195,6 +200,11 @@ enum tcmu_multicast_groups {
>> #define tcmu_cmd_set_dbi(cmd, index) ((cmd)->dbi[(cmd)->dbi_cur++] = (index))
>> #define tcmu_cmd_get_dbi(cmd) ((cmd)->dbi[(cmd)->dbi_cur++])
>>
>> +static inline bool is_in_waiter_list(struct tcmu_dev *udev)
>> +{
>> + return !!udev->waiting_blocks;
>> +}
>> +
>> static void tcmu_cmd_free_data(struct tcmu_cmd *tcmu_cmd, uint32_t len)
>> {
>> struct tcmu_dev *udev = tcmu_cmd->tcmu_dev;
>> @@ -250,8 +260,6 @@ static bool tcmu_get_empty_blocks(struct tcmu_dev *udev,
>> {
>> int i;
>>
>> - udev->waiting_global = false;
>> -
>> for (i = tcmu_cmd->dbi_cur; i < tcmu_cmd->dbi_cnt; i++) {
>> if (!tcmu_get_empty_block(udev, tcmu_cmd))
>> goto err;
>> @@ -259,9 +267,7 @@ static bool tcmu_get_empty_blocks(struct tcmu_dev *udev,
>> return true;
>>
>> err:
>> - udev->waiting_global = true;
>> - /* Try to wake up the unmap thread */
>> - wake_up(&unmap_wait);
>> + udev->waiting_blocks += tcmu_cmd->dbi_cnt - i;
>> return false;
>> }
>>
>> @@ -671,6 +677,7 @@ static inline size_t tcmu_cmd_get_cmd_size(struct tcmu_cmd *tcmu_cmd,
>>
>> while (!is_ring_space_avail(udev, tcmu_cmd, command_size, data_length)) {
>> int ret;
>> + bool is_waiting_blocks = !!udev->waiting_blocks;
> You can use your helper is_in_waiter_list().
>
>> DEFINE_WAIT(__wait);
>>
>> prepare_to_wait(&udev->wait_cmdr, &__wait, TASK_INTERRUPTIBLE);
>> @@ -688,6 +695,18 @@ static inline size_t tcmu_cmd_get_cmd_size(struct tcmu_cmd *tcmu_cmd,
>> return TCM_LOGICAL_UNIT_COMMUNICATION_FAILURE;
>> }
>>
>> + /*
>> + * Try to insert the current udev to waiter list and
>> + * then wake up the unmap thread
>> + */
>> + if (is_waiting_blocks) {
>> + mutex_lock(&root_udev_waiter_mutex);
>> + list_add_tail(&udev->waiter, &root_udev_waiter);
>> + mutex_unlock(&root_udev_waiter_mutex);
>> +
>> + wake_up(&unmap_wait);
>> + }
> Is this supposed to go before the schedule_timeout call?
>
> If we are here and schedule_timeout returned non zero then our wait_cmdr
> has been woken up from the unmap thread because it freed some space, so
> we do not want to again add ourself and call unmap again.
>
>
>> +
>> mutex_lock(&udev->cmdr_lock);
>>
>> /* We dropped cmdr_lock, cmd_head is stale */
>> @@ -902,8 +921,6 @@ static unsigned int tcmu_handle_completions(struct tcmu_dev *udev)
>> if (mb->cmd_tail == mb->cmd_head)
>> del_timer(&udev->timeout); /* no more pending cmds */
>>
>> - wake_up(&udev->wait_cmdr);
>> -
>> return handled;
>> }
>>
>> @@ -996,7 +1013,17 @@ static int tcmu_irqcontrol(struct uio_info *info, s32 irq_on)
>> struct tcmu_dev *tcmu_dev = container_of(info, struct tcmu_dev, uio_info);
>>
>> mutex_lock(&tcmu_dev->cmdr_lock);
>> - tcmu_handle_completions(tcmu_dev);
>> + /*
>> + * If the current udev is also in waiter list, this will
>> + * make sure that the other waiters in list be feeded ahead
>> + * of it.
>> + */
>> + if (is_in_waiter_list(tcmu_dev)) {
>> + wake_up(&unmap_wait);
>> + } else {
>> + tcmu_handle_completions(tcmu_dev);
>> + wake_up(&tcmu_dev->wait_cmdr);
>> + }
>> mutex_unlock(&tcmu_dev->cmdr_lock);
>>
>> return 0;
>> @@ -1231,7 +1258,7 @@ static int tcmu_configure_device(struct se_device *dev)
>> udev->data_off = CMDR_SIZE;
>> udev->data_size = DATA_SIZE;
>> udev->dbi_thresh = 0; /* Default in Idle state */
>> - udev->waiting_global = false;
>> + udev->waiting_blocks = 0;
>>
>> /* Initialise the mailbox of the ring buffer */
>> mb = udev->mb_addr;
>> @@ -1345,6 +1372,13 @@ static void tcmu_free_device(struct se_device *dev)
>> list_del(&udev->node);
>> mutex_unlock(&root_udev_mutex);
>>
>> + mutex_lock(&root_udev_waiter_mutex);
>> + mutex_lock(&udev->cmdr_lock);
>> + if (is_in_waiter_list(udev))
>> + list_del(&udev->waiter);
>> + mutex_unlock(&udev->cmdr_lock);
>> + mutex_unlock(&root_udev_waiter_mutex);
>> +
>> vfree(udev->mb_addr);
>>
>> /* Upper layer should drain all requests before calling this */
>> @@ -1550,6 +1584,7 @@ static int unmap_thread_fn(void *data)
>> struct tcmu_dev *udev;
>> loff_t off;
>> uint32_t start, end, block;
>> + static uint32_t free_blocks;
>> struct page *page;
>> int i;
>>
>> @@ -1571,7 +1606,7 @@ static int unmap_thread_fn(void *data)
>> tcmu_handle_completions(udev);
>>
>> /* Skip the udevs waiting the global pool or in idle */
>> - if (udev->waiting_global || !udev->dbi_thresh) {
>> + if (is_in_waiter_list(udev) || !udev->dbi_thresh) {
>> mutex_unlock(&udev->cmdr_lock);
>> continue;
>> }
>> @@ -1607,17 +1642,32 @@ static int unmap_thread_fn(void *data)
>> }
>> }
>> mutex_unlock(&udev->cmdr_lock);
>> +
>> + free_blocks += end - start;
>> }
>> + mutex_unlock(&root_udev_mutex);
>>
>> /*
>> * Try to wake up the udevs who are waiting
>> - * for the global data pool.
>> + * for the global data pool blocks.
>> */
>> - list_for_each_entry(udev, &root_udev, node) {
>> - if (udev->waiting_global)
>> - wake_up(&udev->wait_cmdr);
>> + mutex_lock(&root_udev_waiter_mutex);
>> + list_for_each_entry(udev, &root_udev_waiter, waiter) {
>> + mutex_lock(&udev->cmdr_lock);
>> + if (udev->waiting_blocks < free_blocks) {
>> + mutex_unlock(&udev->cmdr_lock);
>> + break;
>> + }
>> +
>> + free_blocks -= udev->waiting_blocks;
>> + udev->waiting_blocks = 0;
>> + mutex_unlock(&udev->cmdr_lock);
>> +
>> + list_del(&udev->waiter);
>> +
>> + wake_up(&udev->wait_cmdr);
>> }
>> - mutex_unlock(&root_udev_mutex);
>> + mutex_unlock(&root_udev_waiter_mutex);
>> }
>>
>> return 0;
>>
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