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Re: [Qemu-devel] [PATCH v3] Fixes related to processing of qemu's -numa


From: Eduardo Habkost
Subject: Re: [Qemu-devel] [PATCH v3] Fixes related to processing of qemu's -numa option
Date: Tue, 10 Jul 2012 14:16:52 -0300
User-agent: Mutt/1.5.21 (2010-09-15)

On Thu, Jul 05, 2012 at 09:49:40AM -0700, Chegu Vinod wrote:
> Changes since v2:
>    - Using "unsigned long *" for the node_cpumask[].
>    - Use bitmap_new() instead of g_malloc0() for allocation.
>    - Don't rely on "max_cpus" since it may not be initialized
>      before the numa related qemu options are parsed & processed.
> 
> Note: Continuing to use a new constant for allocation of
>       the mask (This constant is currently set to 255 since
>       with an 8bit APIC ID VCPUs can range from 0-254 in a
>       guest. The APIC ID 255 (0xFF) is reserved for broadcast).

That means that depending on core/thread topology, we may have an even
smaller limit.

(But that will be a problem only after we fix the APIC-ID CPU topology
bug we have)


> 
> 
[...]
> Signed-off-by: Chegu Vinod <address@hidden>, Jim Hull <address@hidden>, Craig 
> Hada <address@hidden>
> Tested-by: Eduardo Habkost <ehabkost <at> redhat.com>

Actually I had not tested this version yet, when you submitted it. But
now I have tested it.

Tested-by: Eduardo Habkost <address@hidden>

Other minor comments below:

> ---
>  cpus.c   |    3 ++-
>  hw/pc.c  |    3 ++-
>  sysemu.h |    3 ++-
>  vl.c     |   48 ++++++++++++++++++++++++++----------------------
>  4 files changed, 32 insertions(+), 25 deletions(-)
> 
> diff --git a/cpus.c b/cpus.c
> index b182b3d..acccd08 100644
> --- a/cpus.c
> +++ b/cpus.c
> @@ -36,6 +36,7 @@
>  #include "cpus.h"
>  #include "qtest.h"
>  #include "main-loop.h"
> +#include "bitmap.h"
>  
>  #ifndef _WIN32
>  #include "compatfd.h"
> @@ -1145,7 +1146,7 @@ void set_numa_modes(void)
>  
>      for (env = first_cpu; env != NULL; env = env->next_cpu) {
>          for (i = 0; i < nb_numa_nodes; i++) {
> -            if (node_cpumask[i] & (1 << env->cpu_index)) {
> +            if (test_bit(env->cpu_index, node_cpumask[i])) {
>                  env->numa_node = i;
>              }
>          }
> diff --git a/hw/pc.c b/hw/pc.c
> index c7e9ab3..2edcc07 100644
> --- a/hw/pc.c
> +++ b/hw/pc.c
> @@ -48,6 +48,7 @@
>  #include "memory.h"
>  #include "exec-memory.h"
>  #include "arch_init.h"
> +#include "bitmap.h"
>  
>  /* output Bochs bios info messages */
>  //#define DEBUG_BIOS
> @@ -639,7 +640,7 @@ static void *bochs_bios_init(void)
>      numa_fw_cfg[0] = cpu_to_le64(nb_numa_nodes);
>      for (i = 0; i < max_cpus; i++) {
>          for (j = 0; j < nb_numa_nodes; j++) {
> -            if (node_cpumask[j] & (1 << i)) {
> +            if (test_bit(i, node_cpumask[j])) {
>                  numa_fw_cfg[i + 1] = cpu_to_le64(j);
>                  break;
>              }
> diff --git a/sysemu.h b/sysemu.h
> index bc2c788..2ce63fc 100644
> --- a/sysemu.h
> +++ b/sysemu.h
> @@ -133,9 +133,10 @@ extern uint8_t qemu_extra_params_fw[2];
>  extern QEMUClock *rtc_clock;
>  
>  #define MAX_NODES 64
> +#define MAX_CPUMASK_BITS 255
>  extern int nb_numa_nodes;
>  extern uint64_t node_mem[MAX_NODES];
> -extern uint64_t node_cpumask[MAX_NODES];
> +extern unsigned long *node_cpumask[MAX_NODES];
>  
>  #define MAX_OPTION_ROMS 16
>  typedef struct QEMUOptionRom {
> diff --git a/vl.c b/vl.c
> index 1329c30..fdd7b74 100644
> --- a/vl.c
> +++ b/vl.c
> @@ -28,6 +28,7 @@
>  #include <errno.h>
>  #include <sys/time.h>
>  #include <zlib.h>
> +#include "bitmap.h"
>  
>  /* Needed early for CONFIG_BSD etc. */
>  #include "config-host.h"
> @@ -240,7 +241,7 @@ QTAILQ_HEAD(, FWBootEntry) fw_boot_order = 
> QTAILQ_HEAD_INITIALIZER(fw_boot_order
>  
>  int nb_numa_nodes;
>  uint64_t node_mem[MAX_NODES];
> -uint64_t node_cpumask[MAX_NODES];
> +unsigned long *node_cpumask[MAX_NODES];
>  
>  uint8_t qemu_uuid[16];
>  
> @@ -950,6 +951,9 @@ static void numa_add(const char *optarg)
>      char *endptr;
>      unsigned long long value, endvalue;
>      int nodenr;
> +    int i;
> +
> +    value = endvalue = 0ULL;
>  
>      optarg = get_opt_name(option, 128, optarg, ',') + 1;
>      if (!strcmp(option, "node")) {
> @@ -970,27 +974,25 @@ static void numa_add(const char *optarg)
>              }
>              node_mem[nodenr] = sval;
>          }
> -        if (get_param_value(option, 128, "cpus", optarg) == 0) {
> -            node_cpumask[nodenr] = 0;
> -        } else {
> +        if (get_param_value(option, 128, "cpus", optarg) != 0) {
>              value = strtoull(option, &endptr, 10);
> -            if (value >= 64) {
> -                value = 63;
> -                fprintf(stderr, "only 64 CPUs in NUMA mode supported.\n");
> +            if (*endptr == '-') {
> +                endvalue = strtoull(endptr+1, &endptr, 10);
>              } else {
> -                if (*endptr == '-') {
> -                    endvalue = strtoull(endptr+1, &endptr, 10);
> -                    if (endvalue >= 63) {
> -                        endvalue = 62;
> -                        fprintf(stderr,
> -                            "only 63 CPUs in NUMA mode supported.\n");
> -                    }
> -                    value = (2ULL << endvalue) - (1ULL << value);
> -                } else {
> -                    value = 1ULL << value;
> -                }
> +                endvalue = value;
> +            }
> +
> +
> +            if (!(endvalue < MAX_CPUMASK_BITS)) {
> +                endvalue = MAX_CPUMASK_BITS - 1;
> +                fprintf(stderr,
> +                    "A max of %d CPUs are supported in a guest\n",
> +                     MAX_CPUMASK_BITS);
> +            }
> +
> +            for (i = value; i <= endvalue; ++i) {
> +                set_bit(i, node_cpumask[nodenr]);
>              }

Nit: you could optimize this using bitmap_set(), but it's not a big
deal.


> -            node_cpumask[nodenr] = value;
>          }
>          nb_numa_nodes++;
>      }
> @@ -2331,7 +2333,8 @@ int main(int argc, char **argv, char **envp)
>  
>      for (i = 0; i < MAX_NODES; i++) {
>          node_mem[i] = 0;
> -        node_cpumask[i] = 0;
> +        node_cpumask[i] = bitmap_new(MAX_CPUMASK_BITS);
> +        bitmap_zero(node_cpumask[i], MAX_CPUMASK_BITS);

bitmap_new() already returns a zeroed bitmap, it seems.

>      }
>  
>      nb_numa_nodes = 0;
> @@ -3469,8 +3472,9 @@ int main(int argc, char **argv, char **envp)
>          }
>  
>          for (i = 0; i < nb_numa_nodes; i++) {
> -            if (node_cpumask[i] != 0)
> +            if (!bitmap_empty(node_cpumask[i], MAX_CPUMASK_BITS)) {
>                  break;
> +            }
>          }
>          /* assigning the VCPUs round-robin is easier to implement, guest OSes
>           * must cope with this anyway, because there are BIOSes out there in
> @@ -3478,7 +3482,7 @@ int main(int argc, char **argv, char **envp)
>           */
>          if (i == nb_numa_nodes) {
>              for (i = 0; i < max_cpus; i++) {
> -                node_cpumask[i % nb_numa_nodes] |= 1 << i;
> +                set_bit(i, node_cpumask[i % nb_numa_nodes]);
>              }
>          }
>      }

Reviewed-by: Eduardo Habkost <address@hidden>

-- 
Eduardo



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