[CRIU] [PATCH 1/1] Use choose_service_fd_base in the root process.

[Andrei Vagin]

Kirill, could you review this patch?

On Thu, Aug 02, 2018 at 02:53:10PM +0200, Radoslaw Burny wrote:
> choose_service_fd_base selects lowest possible numbers for service fds
> to keep fd table of the criu process small, making fork() faster.
> However, this method was only used in child processes, not the root CRIU
> process - thus forks from root were still slow. This fixes the issue.
> 
> Sorry for slightly unreadable patch - the code move was necessary due to
> changes in the inter-function dependencies. The key part of the diff is
> this line:
>   service_fd_base = choose_service_fd_base(NULL);
> 
> Signed-off-by: Radoslaw Burny <rburny at google.com>
> ---
>  criu/util.c | 66 ++++++++++++++++++++++++++---------------------------
>  1 file changed, 33 insertions(+), 33 deletions(-)
> 
> diff --git a/criu/util.c b/criu/util.c
> index ab4d89aa..114756a6 100644
> --- a/criu/util.c
> +++ b/criu/util.c
> @@ -441,27 +441,6 @@ static int service_fd_base;
>  /* Id of current process in shared fdt */
>  static int service_fd_id = 0;
>  
> -int init_service_fd(void)
> -{
> -	struct rlimit64 rlimit;
> -
> -	/*
> -	 * Service FDs are those that most likely won't
> -	 * conflict with any 'real-life' ones
> -	 */
> -
> -	if (syscall(__NR_prlimit64, getpid(), RLIMIT_NOFILE, NULL, &rlimit)) {
> -		pr_perror("Can't get rlimit");
> -		return -1;
> -	}
> -
> -	service_fd_rlim_cur = (int)rlimit.rlim_cur;
> -	service_fd_base = service_fd_rlim_cur;
> -	BUG_ON(service_fd_base < SERVICE_FD_MAX);
> -
> -	return 0;
> -}
> -
>  static int __get_service_fd(enum sfd_type type, int service_fd_id)
>  {
>  	return service_fd_base - type - SERVICE_FD_MAX * service_fd_id;
> @@ -560,20 +539,20 @@ static void move_service_fd(struct pstree_item *me, int type, int new_id, int ne
>  
>  static int choose_service_fd_base(struct pstree_item *me)
>  {
> -	int nr, real_nr, fdt_nr = 1, id = rsti(me)->service_fd_id;
> +	int nr = -1, real_nr, fdt_nr = 1, id = rsti(me)->service_fd_id;
>  
> -	if (rsti(me)->fdt) {
> -		/* The base is set by owner of fdt (id 0) */
> -		if (id != 0)
> -			return service_fd_base;
> -		fdt_nr = rsti(me)->fdt->nr;
> +	if (me != NULL) {
> +		if (rsti(me)->fdt) {
> +			/* The base is set by owner of fdt (id 0) */
> +			if (id != 0)
> +				return service_fd_base;
> +			fdt_nr = rsti(me)->fdt->nr;
> +		}
> +		/* Now find process's max used fd number */
> +		if (!list_empty(&rsti(me)->fds))
> +			nr = list_entry(rsti(me)->fds.prev,
> +					struct fdinfo_list_entry, ps_list)->fe->fd;
>  	}
> -	/* Now find process's max used fd number */
> -	if (!list_empty(&rsti(me)->fds))
> -		nr = list_entry(rsti(me)->fds.prev,
> -				struct fdinfo_list_entry, ps_list)->fe->fd;
> -	else
> -		nr = -1;
>  
>  	nr = max(nr, inh_fd_max);
>  	/*
> @@ -607,6 +586,27 @@ static int choose_service_fd_base(struct pstree_item *me)
>  	return nr;
>  }
>  
> +int init_service_fd(void)
> +{
> +	struct rlimit64 rlimit;
> +
> +	/*
> +	 * Service FDs are those that most likely won't
> +	 * conflict with any 'real-life' ones
> +	 */
> +
> +	if (syscall(__NR_prlimit64, getpid(), RLIMIT_NOFILE, NULL, &rlimit)) {
> +		pr_perror("Can't get rlimit");
> +		return -1;
> +	}
> +
> +	service_fd_rlim_cur = (int)rlimit.rlim_cur;
> +	service_fd_base = choose_service_fd_base(NULL);
> +	BUG_ON(service_fd_base < SERVICE_FD_MAX);
> +
> +	return 0;
> +}
> +
>  int clone_service_fd(struct pstree_item *me)
>  {
>  	int id, new_base, i, ret = -1;
> -- 
> 2.18.0.597.ga71716f1ad-goog
> 
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