[PATCH 3/4] lxc: Implement virtual /proc/cpuinfo via LXC fuse

Daniel Henrique Barboza danielhb413 at gmail.com
Wed Feb 19 12:27:53 UTC 2020



On 2/16/20 2:11 PM, Julio Faracco wrote:
> This commit tries to fix a lots of issues related to LXC VCPUs. One of

Extra 'a' there. "tries to fix lots of issues ..."


> them is related to /proc/cpuinfo content. If only 1 VCPU is set, LXC
> containers will show all CPUs available for host. The second one is
> related to CPU share, if an user set only 1 VCPU, the container/process
> will use all available CPUs. (This is not the case when `cpuset`

This parentesis is never closed.

> attribute is declared. So, this commit adds a virtual cpuinfo based on
> VCPU mapping and it automatic limits the CPU usage according VCPU count.

"and it automatically limits ..."

> 
> Example (now):
> LXC container - 8 CPUS with 2 VCPU:
>      lxc-root# stress --cpu 8
> 
> On host machine, only CPU 0 and 1 have 100% usage.
> 
> Signed-off-by: Julio Faracco <jcfaracco at gmail.com>
> ---
>   src/lxc/lxc_cgroup.c    | 31 ++++++++++++++++
>   src/lxc/lxc_container.c | 15 ++++++++
>   src/lxc/lxc_fuse.c      | 78 ++++++++++++++++++++++++++++++++++++++---
>   3 files changed, 120 insertions(+), 4 deletions(-)
> 
> diff --git a/src/lxc/lxc_cgroup.c b/src/lxc/lxc_cgroup.c
> index 470337e675..a6c73d9d55 100644
> --- a/src/lxc/lxc_cgroup.c
> +++ b/src/lxc/lxc_cgroup.c
> @@ -59,6 +59,34 @@ static int virLXCCgroupSetupCpuTune(virDomainDefPtr def,
>   }
>   
>   
> +static int virLXCCgroupSetupVcpuAuto(virDomainDefPtr def,
> +                                     virCgroupPtr cgroup)
> +{
> +    size_t i;
> +    int vcpumax;
> +    virBuffer buffer = VIR_BUFFER_INITIALIZER;
> +    virBufferPtr cpuset = &buffer;
> +
> +    vcpumax = virDomainDefGetVcpusMax(def);
> +    for (i = 0; i < vcpumax; i++) {
> +        virDomainVcpuDefPtr vcpu = virDomainDefGetVcpu(def, i);
> +        /* Cgroup is smart enough to convert numbers separated
> +         * by comma into ranges. Example: "0,1,2,5," -> "0-2,5".
> +         * Libvirt does not need to process it here. */
> +        if (vcpu)
> +            virBufferAsprintf(cpuset, "%zu,", i);
> +    }
> +    if (virCgroupSetCpusetCpus(cgroup,
> +                               virBufferCurrentContent(cpuset)) < 0) {
> +        virBufferFreeAndReset(cpuset);
> +        return -1;
> +    }
> +
> +    virBufferFreeAndReset(cpuset);
> +    return 0;
> +}
> +
> +
>   static int virLXCCgroupSetupCpusetTune(virDomainDefPtr def,
>                                          virCgroupPtr cgroup,
>                                          virBitmapPtr nodemask)
> @@ -76,6 +104,9 @@ static int virLXCCgroupSetupCpusetTune(virDomainDefPtr def,
>               goto cleanup;
>           /* free mask to make sure we won't use it in a wrong way later */
>           VIR_FREE(mask);
> +    } else {
> +        /* auto mode for VCPU limits */
> +        virLXCCgroupSetupVcpuAuto(def, cgroup);
>       }
>   
>       if (virDomainNumatuneGetMode(def->numa, -1, &mode) < 0 ||
> diff --git a/src/lxc/lxc_container.c b/src/lxc/lxc_container.c
> index 41efe43a14..1a2c97c9f4 100644
> --- a/src/lxc/lxc_container.c
> +++ b/src/lxc/lxc_container.c
> @@ -999,6 +999,7 @@ static int lxcContainerMountProcFuse(virDomainDefPtr def,
>   {
>       int ret;
>       char *meminfo_path = NULL;
> +    char *cpuinfo_path = NULL;


You can use g_autofree on cpuinfo_path to avoid the need for VIR_FREE() in the
end.

>   
>       VIR_DEBUG("Mount /proc/meminfo stateDir=%s", stateDir);
>   
> @@ -1013,7 +1014,21 @@ static int lxcContainerMountProcFuse(virDomainDefPtr def,
>                                meminfo_path);
>       }
>   
> +    VIR_DEBUG("Mount /proc/cpuinfo stateDir=%s", stateDir);
> +
> +    cpuinfo_path = g_strdup_printf("/.oldroot/%s/%s.fuse/cpuinfo",
> +                                   stateDir,
> +                                   def->name);
> +
> +    if ((ret = mount(cpuinfo_path, "/proc/cpuinfo",
> +                     NULL, MS_BIND, NULL)) < 0) {
> +        virReportSystemError(errno,
> +                             _("Failed to mount %s on /proc/cpuinfo"),
> +                             cpuinfo_path);
> +    }
> +
>       VIR_FREE(meminfo_path);
> +    VIR_FREE(cpuinfo_path);
>       return ret;
>   }
>   #else
> diff --git a/src/lxc/lxc_fuse.c b/src/lxc/lxc_fuse.c
> index 44f240a0b5..12fa69d494 100644
> --- a/src/lxc/lxc_fuse.c
> +++ b/src/lxc/lxc_fuse.c
> @@ -37,6 +37,7 @@
>   #if WITH_FUSE
>   
>   static const char *fuse_meminfo_path = "/meminfo";
> +static const char *fuse_cpuinfo_path = "/cpuinfo";
>   
>   static int lxcProcGetattr(const char *path, struct stat *stbuf)
>   {
> @@ -54,7 +55,8 @@ static int lxcProcGetattr(const char *path, struct stat *stbuf)
>       if (STREQ(path, "/")) {
>           stbuf->st_mode = S_IFDIR | 0755;
>           stbuf->st_nlink = 2;
> -    } else if (STREQ(path, fuse_meminfo_path)) {
> +    } else if (STREQ(path, fuse_meminfo_path) ||
> +               STREQ(path, fuse_cpuinfo_path)) {
>           if (stat(mempath, &sb) < 0) {
>               res = -errno;
>               goto cleanup;
> @@ -90,6 +92,7 @@ static int lxcProcReaddir(const char *path, void *buf,
>       filler(buf, ".", NULL, 0);
>       filler(buf, "..", NULL, 0);
>       filler(buf, fuse_meminfo_path + 1, NULL, 0);
> +    filler(buf, fuse_cpuinfo_path + 1, NULL, 0);
>   
>       return 0;
>   }
> @@ -97,7 +100,8 @@ static int lxcProcReaddir(const char *path, void *buf,
>   static int lxcProcOpen(const char *path G_GNUC_UNUSED,
>                          struct fuse_file_info *fi G_GNUC_UNUSED)
>   {
> -    if (STRNEQ(path, fuse_meminfo_path))
> +    if (STRNEQ(path, fuse_meminfo_path) &&
> +        STRNEQ(path, fuse_cpuinfo_path))
>           return -ENOENT;
>   
>       if ((fi->flags & 3) != O_RDONLY)
> @@ -125,7 +129,7 @@ static int lxcProcHostRead(char *path, char *buf, size_t size, off_t offset)
>   static int lxcProcReadMeminfo(char *hostpath, virDomainDefPtr def,
>                                 char *buf, size_t size, off_t offset)
>   {
> -    int res;
> +    int res = -1;
>       FILE *fd = NULL;
>       char *line = NULL;
>       size_t n;
> @@ -151,7 +155,6 @@ static int lxcProcReadMeminfo(char *hostpath, virDomainDefPtr def,
>           goto cleanup;
>       }
>   
> -    res = -1;
>       while (getline(&line, &n, fd) > 0) {
>           char *ptr = strchr(line, ':');
>           if (!ptr)
> @@ -235,6 +238,70 @@ static int lxcProcReadMeminfo(char *hostpath, virDomainDefPtr def,
>       return res;
>   }
>   
> +
> +static int lxcProcReadCpuinfo(char *hostpath, virDomainDefPtr def,
> +                              char *buf, size_t size, off_t offset)
> +{
> +    int res = -1;
> +    FILE *fd = NULL;


I believe that instead of creating the fd as FILE you can use

VIR_AUTOCLOSE fd = -1;


And it will auto close the fd for you when context is gone. Then you won't
need VIR_FORCE_FCLOSE().


> +    char *line = NULL;


'line' can use g_autofree as well.


> +    size_t n;
> +    virBuffer buffer = VIR_BUFFER_INITIALIZER;
> +    virBufferPtr new_cpuinfo = &buffer;
> +    size_t cpu;
> +    size_t nvcpu;
> +    size_t curcpu = 0;
> +    bool get_proc = false;
> +
> +    fd = fopen(hostpath, "r");


Suggestion: fopen() here is fine, but I believe that you can use utilities like
virFileReadAll() as well. It will give you a buffer with the file contents so
you don't need to rely on sscanf() and getline() in the loop below.


> +    if (fd == NULL) {
> +        virReportSystemError(errno, _("Cannot open %s"), hostpath);
> +        res = -errno;
> +        goto cleanup;
> +    }
> +
> +    /* /proc/cpuinfo does not support fseek */
> +    if (offset > 0) {
> +        res = 0;
> +        goto cleanup;
> +    }
> +
> +    nvcpu = virDomainDefGetVcpus(def);
> +    while (getline(&line, &n, fd) > 0) {
> +        if (sscanf(line, "processor\t: %zu", &cpu) == 1) {
> +            virDomainVcpuDefPtr vcpu = virDomainDefGetVcpu(def, cpu);
> +            /* VCPU is mapped */
> +            if (vcpu) {
> +                if (curcpu == nvcpu)
> +                    break;
> +
> +                virBufferAsprintf(new_cpuinfo, "processor\t: %zu\n",
> +                                  curcpu);
> +                curcpu++;
> +                get_proc = true;
> +            } else {
> +                get_proc = false;
> +            }
> +        } else {
> +            /* It is not a processor index */
> +            if (get_proc)
> +                virBufferAdd(new_cpuinfo, line, -1);
> +        }
> +    }
> +
> +    res = strlen(virBufferCurrentContent(new_cpuinfo));
> +    if (res > size)
> +        res = size;
> +    memcpy(buf, virBufferCurrentContent(new_cpuinfo), res);
> +
> + cleanup:
> +    VIR_FREE(line);
> +    virBufferFreeAndReset(new_cpuinfo);
> +    VIR_FORCE_FCLOSE(fd);
> +    return res;
> +}
> +
> +
>   static int lxcProcRead(const char *path G_GNUC_UNUSED,
>                          char *buf G_GNUC_UNUSED,
>                          size_t size G_GNUC_UNUSED,
> @@ -254,6 +321,9 @@ static int lxcProcRead(const char *path G_GNUC_UNUSED,
>       if (STREQ(path, fuse_meminfo_path)) {
>           if ((res = lxcProcReadMeminfo(hostpath, def, buf, size, offset)) < 0)
>               res = lxcProcHostRead(hostpath, buf, size, offset);
> +    } else if (STREQ(path, fuse_cpuinfo_path)) {
> +        if ((res = lxcProcReadCpuinfo(hostpath, def, buf, size, offset)) < 0)
> +            res = lxcProcHostRead(hostpath, buf, size, offset);
>       }
>   
>       VIR_FREE(hostpath);
> 




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