Re: [RFC PATCH v4] xen: credit2: provide custom option to create runqueue

[Praveen Kumar <kpraveen.lkml@gmail.com>]

Hi,

Can you please provide comments on the shared patch.
Thanks in advance.

Regards,

~Praveen.

On Wed, 2017-04-19 at 23:15 +0530, Praveen Kumar wrote:
> The patch introduces a new, very flexible way of arranging runqueues
> in Credit2.
> It allows to specify, explicitly and precisely, what pCPUs should
> belong to
> which runqueue.
> 
> Signed-off-by: Praveen Kumar <kpraveen.lkml@gmail.com>
> ---
>  docs/misc/xen-command-line.markdown |  10 ++-
>  xen/common/sched_credit2.c          | 167
> +++++++++++++++++++++++++++++++++++-
>  2 files changed, 174 insertions(+), 3 deletions(-)
> 
> diff --git a/docs/misc/xen-command-line.markdown b/docs/misc/xen-
> command-line.markdown
> index 33e54aef63..f2ee4ad972 100644
> --- a/docs/misc/xen-command-line.markdown
> +++ b/docs/misc/xen-command-line.markdown
> @@ -525,7 +525,7 @@ also slow in responding to load changes.
>  The default value of `1 sec` is rather long.
>  
>  ### credit2\_runqueue
> -> `= cpu | core | socket | node | all`
> +> `= cpu | core | socket | node | all | <custom>`
>  
>  > Default: `socket`
>  
> @@ -543,6 +543,14 @@ Available alternatives, with their meaning, are:
>  * `node`: one runqueue per each NUMA node of the host;
>  * `all`: just one runqueue shared by all the logical pCPUs of
>           the host
> +* `<custom>`: one runqueue per mentioned subset. The subset can be
> defined as
> +              as shown in below example:
> +              credit2_runqueue=[[0,1,][2,6][3,5][4,7]] , or
> 0,1\;2,6\;3,5\;4,7
> +              which means :
> +                  - pCPUs 0 and 1 belong to runqueue 0
> +                  - pCPUs 2 and 6 belong to runqueue 1
> +                  - pCPUs 3 and 5 belong to runqueue 2
> +                  - pCPUs 4 and 7 belong to runqueue 3
>  
>  ### dbgp
>  > `= ehci[ <integer> | @pci<bus>:<slot>.<func> ]`
> diff --git a/xen/common/sched_credit2.c b/xen/common/sched_credit2.c
> index b9b928347f..ebec33f450 100644
> --- a/xen/common/sched_credit2.c
> +++ b/xen/common/sched_credit2.c
> @@ -321,6 +321,16 @@ integer_param("credit2_balance_over",
> opt_overload_balance_tolerance);
>   *           (logical) processors of the host belong. This will
> happen if
>   *           the opt_runqueue parameter is set to 'all'.
>   *
> + * - custom: meaning that there will be one runqueue per subset
> being passed as
> + *           parameter to credit2_runqueue as shown in below
> example.
> + *           Example:
> + *           credit2_runqueue=[[cpu0,cpu1][cpu3][cpu4,cpu5]] or
> + *           credit2_runqueue=0,1\;3\;4,5
> + *           The example mentioned states :
> + *               cpu0 and cpu1 belongs to runqueue 0
> + *               cpu3 belongs to runqueue 1
> + *               cpu4 and cpu5 belongs to runqueue 2
> + *
>   * Depending on the value of opt_runqueue, therefore, cpus that are
> part of
>   * either the same physical core, the same physical socket, the same
> NUMA
>   * node, or just all of them, will be put together to form
> runqueues.
> @@ -330,15 +340,138 @@ integer_param("credit2_balance_over",
> opt_overload_balance_tolerance);
>  #define OPT_RUNQUEUE_SOCKET 2
>  #define OPT_RUNQUEUE_NODE   3
>  #define OPT_RUNQUEUE_ALL    4
> +#define OPT_RUNQUEUE_CUSTOM 5
>  static const char *const opt_runqueue_str[] = {
>      [OPT_RUNQUEUE_CPU] = "cpu",
>      [OPT_RUNQUEUE_CORE] = "core",
>      [OPT_RUNQUEUE_SOCKET] = "socket",
>      [OPT_RUNQUEUE_NODE] = "node",
> -    [OPT_RUNQUEUE_ALL] = "all"
> +    [OPT_RUNQUEUE_ALL] = "all",
> +    [OPT_RUNQUEUE_CUSTOM] = "custom"
>  };
>  static int __read_mostly opt_runqueue = OPT_RUNQUEUE_SOCKET;
>  
> +static unsigned long __read_mostly custom_cpu_runqueue[NR_CPUS];
> +
> +static inline int getlen(const char *start, const char *end)
> +{
> +    if ( ( start ) && ( end ) && ( end > start ) )
> +        return end-start;
> +    else
> +        return -1;
> +}
> +
> +static int parse_custom_runqueue_option(const char *s)
> +{
> +    const char *parse = NULL, *s_end = NULL;
> +    const char *start = NULL, *end = NULL;
> +    char delimiter[2] = {0};
> +    int cpu_added_to_runqueue = 0;
> +    int runqueue = 0;
> +
> +    /* Format supported :
> +     * [[0,1,4,5][2,3,6,7][8,9,12,13][10,11,14,15]]
> +     *                  or
> +     * 0,1,4,5\;2,3,6,7\;8,9,12,13\;10,11,14,15
> +     */
> +    parse = s;
> +    s_end = s + strlen(s);
> +    /* The start and should always be in format of '[..]' */
> +    if ( ( '[' == *parse ) && ( ']' == *(s_end-1)) )
> +    {
> +        delimiter[0] = '[';
> +        delimiter[1] = '\0';
> +        parse++;
> +    }
> +    else
> +    {
> +        delimiter[0] = ';';
> +        delimiter[1] = '\0';
> +    }
> +
> +    while ( ( parse != NULL ) && ( parse < s_end ) )
> +    {
> +        const char *token_sub_str = NULL;
> +
> +        while ( *parse == '[' )
> +            parse++;
> +
> +        start = parse;
> +        end = strstr(parse, delimiter);
> +
> +        /* Check if we don't have the delimiter */
> +        if ( !end )
> +        {
> +            /* If we don't have delimiter, then break, if start is
> greater than
> +             * or equal to s_end, as we have reached the end.
> +             */
> +            if ( start >= s_end )
> +                break;
> +
> +            /* We need to parse till s_end, as we have the last set
> */
> +            end = s_end;
> +        }
> +
> +        /* Just move to next, as we have empty set like [] or ;; */
> +        if ( getlen ( start, end ) < 1 )
> +            goto next;
> +
> +        /*
> +         * find token within the subset
> +         */
> +        do
> +        {
> +            unsigned long token = 0;
> +
> +            /* Get cpu ids separated by ',' within each set */
> +            token_sub_str = strpbrk(start, ",");
> +
> +            /* Basic checks to validate the last entry in subset */
> +            if ( ( !token_sub_str && start < end ) ||
> +                ( token_sub_str > end && token_sub_str > start ) )
> +            {
> +                if ( ( delimiter[0] == '[' ) && ( start == s_end - 1
> ) )
> +                    goto next;
> +
> +                token_sub_str = end;
> +            }
> +
> +            /* Just move to next, as we have empty set like [] or ;;
> */
> +            if ( getlen(start, token_sub_str) < 1 )
> +                goto next;
> +
> +            token = simple_strtoul(start ,&token_sub_str, 0);
> +
> +            if ( token >= nr_cpu_ids)
> +                return -1;
> +
> +            /* If not set already */
> +            if ( custom_cpu_runqueue[token] == -1 )
> +            {
> +                custom_cpu_runqueue[token] = runqueue;
> +                cpu_added_to_runqueue = 1;
> +            }
> +            else
> +                return -1;
> +
> +            if ( !token_sub_str || token_sub_str > end )
> +                goto next;
> +
> +            start = ++token_sub_str;
> +        } while ( start < end );
> +next:
> +        if ( cpu_added_to_runqueue )
> +        {
> +            runqueue++;
> +            cpu_added_to_runqueue = 0;
> +        }
> +
> +        parse = ++end;
> +    }
> +    opt_runqueue = OPT_RUNQUEUE_CUSTOM;
> +    return 0;
> +}
> +
>  static void parse_credit2_runqueue(const char *s)
>  {
>      unsigned int i;
> @@ -351,8 +484,29 @@ static void parse_credit2_runqueue(const char
> *s)
>              return;
>          }
>      }
> +    /*
> +     * At this stage we are either unknown value of credit2_runqueue
> or we can
> +     * consider it to be custom cpu. Lets try parsing the same.
> +     * Resetting the custom_cpu_runqueue for future use. Only the
> non-negative
> +     * entries will be valid. The index 'i' in custom_cpu_runqueue
> will store
> +     * the specific runqueue it belongs to.
> +     * Example:
> +     *     If custom_cpu_runqueue[3] == 2
> +     *     Then, it means that cpu 3 belong to runqueue 2.
> +     *     If custom_cpu_runqueue[4] == -1
> +     *     Then, it means that cpu 4 doesn't belong to any runqueue.
> +     */
> +    for ( i = 0; i < nr_cpu_ids; i++ )
> +        custom_cpu_runqueue[i] = -1;
>  
> -    printk("WARNING, unrecognized value of credit2_runqueue
> option!\n");
> +    if ( parse_custom_runqueue_option(s) != 0 )
> +    {
> +        /* Resetting in case of failure, so that we don't mess-up
> during any failure
> +         * due to wrong or spurious pattern passed by user.
> +         */
> +        opt_runqueue = OPT_RUNQUEUE_SOCKET;
> +        printk("WARNING, unrecognized value of credit2_runqueue
> option!\n");
> +    }
>  }
>  custom_param("credit2_runqueue", parse_credit2_runqueue);
>  
> @@ -662,6 +816,15 @@ cpu_to_runqueue(struct csched2_private *prv,
> unsigned int cpu)
>      struct csched2_runqueue_data *rqd;
>      unsigned int rqi;
>  
> +    if ( opt_runqueue == OPT_RUNQUEUE_CUSTOM )
> +    {
> +        if ( custom_cpu_runqueue[cpu] != -1 )
> +        {
> +            BUG_ON(custom_cpu_runqueue[cpu] >= nr_cpu_ids);
> +            return custom_cpu_runqueue[cpu];
> +        }
> +    }
> +
>      for ( rqi = 0; rqi < nr_cpu_ids; rqi++ )
>      {
>          unsigned int peer_cpu;

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