[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index] [Xen-changelog] [xen master] libxl: Make 'xl vcpu-set' work properly on overcommited hosts with an override.
commit afab6f6788b3e1eeed7fd7d2550bca96edca2720 Author: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> AuthorDate: Mon May 13 15:29:14 2013 -0400 Commit: Ian Campbell <ian.campbell@xxxxxxxxxx> CommitDate: Tue May 14 10:02:13 2013 +0100 libxl: Make 'xl vcpu-set' work properly on overcommited hosts with an override. The libxl_cpu_bitmap_alloc(..) function, if provided with a zero value for max CPUs will call xc_get_max_cpus() which will retrieve the number of physical CPUs the host has. This is usually OK if the guest's maxvcpus <= host pcpus. But if the value is different, then the bitmap for VCPUs is limited by the number of CPUs the host has. This is incorrect as what we want is to hotplug in the guest the amount of CPUs that the user specified on the command line and not be limited by the amount of physical CPUs. This means that a guest config like this: vcpus=8 maxvcpus=32 and on a 4 PCPU machine doing xl vcpu-set <guest name> 16 won't work. This is b/c the the size of the bitmap is one byte so it can only hold up to 8 VCPUs. Hence anything above that is going to be ignored. Note that this patch also fixes the bitmap setting - as it would set all of the bits allowed. Meaning if the user had a 4PCPU host we would still allow the user to set 8VCPUs. This second iteration of the patch fixes this. Note that all of the libxl_cpu_bitmap_[test|set] silently ignore any test or sets above its size: if (bit >= bitmap->size * 8) return 0; so we were never notified off this bug. This patch warns the user if they are trying to do this. If the user really wants to do this they have to provide the --ignore-host parameter to bypass this check. Signed-off-by: Konrad Rzeszutek Wilk <konrad.wilk@xxxxxxxxxx> Acked-by: Ian Campbell <ian.campbell@xxxxxxxxxx> Acked-by: Ian Jackson <Ian.Jackson@xxxxxxxxxxxxx> --- tools/libxl/xl_cmdimpl.c | 35 +++++++++++++++++++++++++++++------ tools/libxl/xl_cmdtable.c | 3 ++- 2 files changed, 31 insertions(+), 7 deletions(-) diff --git a/tools/libxl/xl_cmdimpl.c b/tools/libxl/xl_cmdimpl.c index 497d84d..e13a64e 100644 --- a/tools/libxl/xl_cmdimpl.c +++ b/tools/libxl/xl_cmdimpl.c @@ -4487,7 +4487,7 @@ int main_vcpupin(int argc, char **argv) return 0; } -static void vcpuset(uint32_t domid, const char* nr_vcpus) +static void vcpuset(uint32_t domid, const char* nr_vcpus, int check_host) { char *endptr; unsigned int max_vcpus, i; @@ -4499,7 +4499,22 @@ static void vcpuset(uint32_t domid, const char* nr_vcpus) return; } - if (libxl_cpu_bitmap_alloc(ctx, &cpumap, 0)) { + /* + * Maximum amount of vCPUS the guest is allowed to set is limited + * by the host's amount of pCPUs. + */ + if (check_host) { + unsigned int host_cpu = libxl_get_max_cpus(ctx); + if (max_vcpus > host_cpu) { + fprintf(stderr, "You are overcommmitting! You have %d physical " \ + " CPUs and want %d vCPUs! Aborting, use --ignore-host to " \ + " continue\n", host_cpu, max_vcpus); + return; + } + /* NB: This also limits how many are set in the bitmap */ + max_vcpus = (max_vcpus > host_cpu ? host_cpu : max_vcpus); + } + if (libxl_cpu_bitmap_alloc(ctx, &cpumap, max_vcpus)) { fprintf(stderr, "libxl_cpu_bitmap_alloc failed\n"); return; } @@ -4514,13 +4529,21 @@ static void vcpuset(uint32_t domid, const char* nr_vcpus) int main_vcpuset(int argc, char **argv) { - int opt; + static struct option opts[] = { + {"ignore-host", 0, 0, 'i'}, + {0, 0, 0, 0} + }; + int opt, check_host = 1; - SWITCH_FOREACH_OPT(opt, "", NULL, "vcpu-set", 2) { - /* No options */ + SWITCH_FOREACH_OPT(opt, "i", opts, "vcpu-set", 2) { + case 'i': + check_host = 0; + break; + default: + break; } - vcpuset(find_domain(argv[optind]), argv[optind+1]); + vcpuset(find_domain(argv[optind]), argv[optind + 1], check_host); return 0; } diff --git a/tools/libxl/xl_cmdtable.c b/tools/libxl/xl_cmdtable.c index 26f5025..44b42b0 100644 --- a/tools/libxl/xl_cmdtable.c +++ b/tools/libxl/xl_cmdtable.c @@ -217,7 +217,8 @@ struct cmd_spec cmd_table[] = { { "vcpu-set", &main_vcpuset, 0, 1, "Set the number of active VCPUs allowed for the domain", - "<Domain> <vCPUs>", + "[option] <Domain> <vCPUs>", + "-i, --ignore-host Don't limit the vCPU based on the host CPU count", }, { "vm-list", &main_vm_list, 0, 0, -- generated by git-patchbot for /home/xen/git/xen.git#master _______________________________________________ Xen-changelog mailing list Xen-changelog@xxxxxxxxxxxxx http://lists.xensource.com/xen-changelog
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