Re: [Xen-devel] [PATCH 4/4] tools: add total/local memory bandwith monitoring

[Wei Liu <wei.liu2@xxxxxxxxxx>]

On Tue, Dec 23, 2014 at 04:54:39PM +0800, Chao Peng wrote:
[...]
> +static int libxl__psr_cmt_get_mem_bandwidth(libxl__gc *gc, uint32_t domid,
> +    xc_psr_cmt_type type, uint32_t socketid, uint32_t *bandwidth)
> +{
> +    uint64_t sample1, sample2;
> +    uint32_t upscaling_factor;
> +    int rc;
> +
> +    rc = libxl__psr_cmt_get_l3_monitoring_data(gc, domid,
> +                    type, socketid, &sample1);
> +    if (rc < 0)
> +        return ERROR_FAIL;
> +
> +    usleep(10000);
> +
> +    rc = libxl__psr_cmt_get_l3_monitoring_data(gc, domid,
> +                    type, socketid, &sample2);
> +    if (rc < 0)
> +       return ERROR_FAIL;
> +
> +    if (sample2 < sample1) {
> +         LOGE(ERROR, "event counter overflowed between two samplings");
> +         return ERROR_FAIL;
> +    }
> +

What's the likelihood of counter overflows? Can we handle this more
gracefully? Say, retry (with maximum retry cap) when counter overflows?

> +    rc = xc_psr_cmt_get_l3_upscaling_factor(CTX->xch, &upscaling_factor);
> +    if (rc < 0) {
> +        LOGE(ERROR, "failed to get L3 upscaling factor");
> +        return ERROR_FAIL;
> +    }
> +
> +    *bandwidth = (sample2 - sample1) * 100 *  upscaling_factor / 1024;
> +    return rc;
> +}
> +
> +int libxl_psr_cmt_get_total_mem_bandwidth(libxl_ctx *ctx, uint32_t domid,
> +    uint32_t socketid, uint32_t *bandwidth)
> +{
> +    GC_INIT(ctx);
> +    int rc;
> +
> +    rc = libxl__psr_cmt_get_mem_bandwidth(gc, domid,
> +                    XC_PSR_CMT_TOTAL_MEM_BANDWIDTH, socketid, bandwidth);
> +    GC_FREE;
> +    return rc;
> +}
> +
> +int libxl_psr_cmt_get_local_mem_bandwidth(libxl_ctx *ctx, uint32_t domid,
> +    uint32_t socketid, uint32_t *bandwidth)
> +{
> +    GC_INIT(ctx);
> +    int rc;
> +
> +    rc = libxl__psr_cmt_get_mem_bandwidth(gc, domid,
> +                    XC_PSR_CMT_LOCAL_MEM_BANDWIDTH, socketid, bandwidth);
> +    GC_FREE;
> +    return rc;
> +}
> +
>  /*
>   * Local variables:
>   * mode: C
> diff --git a/tools/libxl/libxl_types.idl b/tools/libxl/libxl_types.idl
> index f7fc695..8029a39 100644
> --- a/tools/libxl/libxl_types.idl
> +++ b/tools/libxl/libxl_types.idl
> @@ -693,4 +693,6 @@ libxl_event = Struct("event",[
>  
>  libxl_psr_cmt_type = Enumeration("psr_cmt_type", [
>      (1, "CACHE_OCCUPANCY"),
> +    (2, "TOTAL_MEM_BANDWIDTH"),
> +    (3, "LOCAL_MEM_BANDWIDTH"),
>      ])
> diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c
> index f4534ec..e0435dd 100644
> --- a/tools/libxl/xl_cmdimpl.c
> +++ b/tools/libxl/xl_cmdimpl.c
> @@ -7867,6 +7867,16 @@ static void psr_cmt_print_domain_l3_info(libxl_dominfo 
> *dominfo,
>                   socketid, &data) )
>                  printf("%13u KB", data);
>              break;
> +        case LIBXL_PSR_CMT_TYPE_TOTAL_MEM_BANDWIDTH:
> +            if ( !libxl_psr_cmt_get_total_mem_bandwidth(ctx, dominfo->domid,

Coding style.

> +                 socketid, &data) )
> +                printf("%11u KB/s", data);
> +            break;
> +        case LIBXL_PSR_CMT_TYPE_LOCAL_MEM_BANDWIDTH:
> +            if ( !libxl_psr_cmt_get_local_mem_bandwidth(ctx, dominfo->domid,

Ditto.

Wei.

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