On 11/13/2012 05:54 AM, Viktor Mihajlovski wrote:
> Since /sys/devices/system/cpu/present is not available on
> older kernels like on RHEL 5.x nodeGetCPUCount will
> fail there. The fallback implemented is to scan for
> /sys/devices/system/cpu/cpuNN entries.
>
> Signed-off-by: Viktor Mihajlovski <mihajlov@xxxxxxxxxxxxxxxxxx>
> ---
> src/nodeinfo.c | 33 ++++++++++++++++++++++++++++-----
> 1 file changed, 28 insertions(+), 5 deletions(-)
> #ifdef __linux__
> - /* XXX should we also work on older kernels, like RHEL5, that lack
> - * cpu/present and cpu/online files? Those kernels also lack cpu
> - * hotplugging, so it would be a matter of finding the largest
> - * cpu/cpuNN directory, and returning NN + 1 */
> - return linuxParseCPUmax(SYSFS_SYSTEM_PATH "/cpu/present");
> + /* to support older kernels, like RHEL5, that lack
> + * cpu/present we fall back to count cpu/cpuNN
> + * entries.
> + */
> + char *cpupath = NULL;
> + int i = 0;
> +
> + if (virFileExists(SYSFS_SYSTEM_PATH "/cpu/present")) {
> + i = linuxParseCPUmax(SYSFS_SYSTEM_PATH "/cpu/present");
> + } else if (virFileExists(SYSFS_SYSTEM_PATH "/cpu/cpu0")) {
> + do {
> + i++;
> + VIR_FREE(cpupath);
> + if (virAsprintf(&cpupath, "%s/cpu/cpu%d",
> + SYSFS_SYSTEM_PATH, i) < 0) {
> + virReportOOMError();
> + return -1;
> + }
> + } while (virFileExists(cpupath));
The assumption here is that any kernel lacking cpu/present also lacks
hotplug, and therefore the cpuNN will be consecutive and we aren't going
to miss anything. You removed that assumption from the comment, but I
think it is important to leave in.
ACK. I'm firing up my RHEL 5 VM to test this before I push with this
comment change, but it looks sane.
diff --git i/src/nodeinfo.c w/src/nodeinfo.c
index cea3775..4589b77 100644
--- i/src/nodeinfo.c
+++ w/src/nodeinfo.c
@@ -978,9 +978,10 @@ int
nodeGetCPUCount(void)
{
#ifdef __linux__
- /* to support older kernels, like RHEL5, that lack
- * cpu/present we fall back to count cpu/cpuNN
- * entries.
+ /* To support older kernels that lack cpu/present, such as 2.6.18
+ * in RHEL5, we fall back to count cpu/cpuNN entries; this assumes
+ * that such kernels also lack hotplug, and therefore cpu/cpuNN
+ * will be consecutive.
*/
char *cpupath = NULL;
int i = 0;
--
Eric Blake eblake@xxxxxxxxxx +1-919-301-3266
Libvirt virtualization library http://libvirt.org
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