Re: [Xen-devel] [PATCH 7 of 8] xl: free memory before building a domain

[Christoph Egger <Christoph.Egger@xxxxxxx>]

On Friday 27 August 2010 13:19:19 Stefano Stabellini wrote:
> xl: free memory before building a domain
>
> Free the needed amount of memory before proceeding with the domain
> build.
> Use a filelock to prevent other xl instances from conflicting during
> this operation.
>
> Signed-off-by: Stefano Stabellini <stefano.stabellini@xxxxxxxxxxxxx>
>
> diff -r b80a1688b5c9 tools/examples/xl.conf
> --- a/tools/examples/xl.conf  Thu Aug 26 18:03:20 2010 +0100
> +++ b/tools/examples/xl.conf  Thu Aug 26 18:26:04 2010 +0100
> @@ -3,3 +3,6 @@
>  # automatically balloon down dom0 when xen doesn't have enough free
>  # memory to create a domain
>  autoballon=1
> +
> +# full path of the lockfile used by xl during domain creation
> +lockfile="/var/lock/xl"
> diff -r b80a1688b5c9 tools/libxl/xl.c
> --- a/tools/libxl/xl.c        Thu Aug 26 18:03:20 2010 +0100
> +++ b/tools/libxl/xl.c        Thu Aug 26 18:26:04 2010 +0100
> @@ -34,6 +34,7 @@
>
>  xentoollog_logger_stdiostream *logger;
>  int autoballoon = 1;
> +char *lockfile = "/var/lock/xl";

NetBSD doesn't have /var/lock. Is it ok to use /var/lib ?

Christoph


>
>  static xentoollog_level minmsglevel = XTL_PROGRESS;
>
> @@ -44,6 +45,7 @@ static void parse_global_config(const ch
>      long l;
>      XLU_Config *config;
>      int e;
> +    const char *buf;
>
>      config = xlu_cfg_init(stderr, configfile);
>      if (!config) {
> @@ -60,6 +62,9 @@ static void parse_global_config(const ch
>      if (!xlu_cfg_get_long (config, "autoballoon", &l))
>          autoballoon = l;
>
> +    if (!xlu_cfg_get_string (config, "lockfile", &buf))
> +        lockfile = strdup(buf);
> +
>      xlu_cfg_destroy(config);
>  }
>
> diff -r b80a1688b5c9 tools/libxl/xl.h
> --- a/tools/libxl/xl.h        Thu Aug 26 18:03:20 2010 +0100
> +++ b/tools/libxl/xl.h        Thu Aug 26 18:26:04 2010 +0100
> @@ -92,5 +92,6 @@ extern xentoollog_logger_stdiostream *lo
>
>  /* global options */
>  extern int autoballoon;
> +extern char *lockfile;
>
>  #endif /* XL_H */
> diff -r b80a1688b5c9 tools/libxl/xl_cmdimpl.c
> --- a/tools/libxl/xl_cmdimpl.c        Thu Aug 26 18:03:20 2010 +0100
> +++ b/tools/libxl/xl_cmdimpl.c        Thu Aug 26 18:26:04 2010 +0100
> @@ -68,6 +68,7 @@ libxl_ctx ctx;
>  /* when we operate on a domain, it is this one: */
>  static uint32_t domid;
>  static const char *common_domname;
> +static int fd_lock = -1;
>
>
>  static const char savefileheader_magic[32]=
> @@ -234,6 +235,65 @@ static void find_domain(const char *p)
>      common_domname = was_name ? p : libxl_domid_to_name(&ctx, domid);
>  }
>
> +static int acquire_lock(void)
> +{
> +    int rc;
> +    struct flock fl;
> +
> +    /* lock already acquired */
> +    if (fd_lock >= 0)
> +        return ERROR_INVAL;
> +
> +    fl.l_type = F_WRLCK;
> +    fl.l_whence = SEEK_SET;
> +    fl.l_start = 0;
> +    fl.l_len = 0;
> +    fd_lock = open(lockfile, O_WRONLY|O_CREAT, S_IWUSR);
> +    if (fd_lock < 0) {
> +        fprintf(stderr, "cannot open the lockfile %s errno=%d\n",
> lockfile, errno); +        return ERROR_FAIL;
> +    }
> +get_lock:
> +    rc = fcntl(fd_lock, F_SETLKW, &fl);
> +    if (rc < 0 && errno == EINTR)
> +        goto get_lock;
> +    if (rc < 0) {
> +        fprintf(stderr, "cannot acquire lock %s errno=%d\n", lockfile,
> errno); +        rc = ERROR_FAIL;
> +    } else
> +        rc = 0;
> +    return rc;
> +}
> +
> +static int release_lock(void)
> +{
> +    int rc;
> +    struct flock fl;
> +
> +    /* lock not acquired */
> +    if (fd_lock < 0)
> +        return ERROR_INVAL;
> +
> +release_lock:
> +    fl.l_type = F_UNLCK;
> +    fl.l_whence = SEEK_SET;
> +    fl.l_start = 0;
> +    fl.l_len = 0;
> +
> +    rc = fcntl(fd_lock, F_SETLKW, &fl);
> +    if (rc < 0 && errno == EINTR)
> +        goto release_lock;
> +    if (rc < 0) {
> +        fprintf(stderr, "cannot release lock %s, errno=%d\n", lockfile,
> errno); +        rc = ERROR_FAIL;
> +    } else
> +        rc = 0;
> +    close(fd_lock);
> +    fd_lock = -1;
> +
> +    return rc;
> +}
> +
>  #define LOG(_f, _a...)   dolog(__FILE__, __LINE__, __func__, _f "\n",
> ##_a)
>
>  static void dolog(const char *file, int line, const char *func, char *fmt,
> ...) @@ -1209,6 +1269,48 @@ struct domain_create {
>      char **migration_domname_r;
>  };
>
> +static int freemem(libxl_domain_build_info *b_info,
> libxl_device_model_info *dm_info) +{
> +    int rc, retries = 3;
> +    uint32_t need_memkb, free_memkb;
> +
> +    if (!autoballoon)
> +        return 0;
> +
> +    rc = libxl_domain_need_memory(&ctx, b_info, dm_info, &need_memkb);
> +    if (rc < 0)
> +        return rc;
> +
> +    do {
> +        rc = libxl_get_free_memory(&ctx, &free_memkb);
> +        if (rc < 0)
> +            return rc;
> +
> +        if (free_memkb >= need_memkb)
> +            return 0;
> +
> +        rc = libxl_set_relative_memory_target(&ctx, 0, free_memkb -
> need_memkb, 0); +        if (rc < 0)
> +            return rc;
> +
> +        rc = libxl_wait_for_free_memory(&ctx, domid, need_memkb, 10);
> +        if (!rc)
> +            return 0;
> +        else if (rc != ERROR_NOMEM)
> +            return rc;
> +
> +        /* the memory target has been reached but the free memory is still
> +         * not enough: loop over again */
> +        rc = libxl_wait_for_memory_target(&ctx, 0, 1);
> +        if (rc < 0)
> +            return rc;
> +
> +        retries--;
> +    } while (retries > 0);
> +
> +    return ERROR_NOMEM;
> +}
> +
>  static int create_domain(struct domain_create *dom_info)
>  {
>      struct domain_config d_config;
> @@ -1367,6 +1469,17 @@ static int create_domain(struct domain_c
>  start:
>      domid = 0;
>
> +    rc = acquire_lock();
> +    if (rc < 0)
> +        goto error_out;
> +
> +    ret = freemem(&d_config.b_info, &dm_info);
> +    if (ret < 0) {
> +        fprintf(stderr, "failed to free memory for the domain\n");
> +        ret = ERROR_FAIL;
> +        goto error_out;
> +    }
> +
>      ret = libxl_domain_make(&ctx, &d_config.c_info, &domid);
>      if (ret) {
>          fprintf(stderr, "cannot make domain: %d\n", ret);
> @@ -1475,6 +1588,8 @@ start:
>              goto error_out;
>      }
>
> +    release_lock();
> +
>      if (!paused)
>          libxl_domain_unpause(&ctx, domid);
>
> @@ -1612,6 +1727,7 @@ start:
>      }
>
>  error_out:
> +    release_lock();
>      if (domid)
>          libxl_domain_destroy(&ctx, domid, 0);
>
>
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> Xen-devel@xxxxxxxxxxxxxxxxxxx
> http://lists.xensource.com/xen-devel



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