[CRIU] [PATCH v2 12/14] files: Make tasks set their own service_fd_base
Kirill Tkhai
ktkhai at virtuozzo.com
Fri Dec 29 11:58:25 MSK 2017
On 28.12.2017 22:00, Andrei Vagin wrote:
> On Thu, Dec 28, 2017 at 04:10:29PM +0300, Kirill Tkhai wrote:
>> Currently, we set rlim(RLIMIT_NOFILE) unlimited
>> and service_fd_rlim_cur to place service fds.
>> This leads to a signify problem: every task uses
>> the biggest possible files_struct in kernel, and
>> it consumes excess memory after restore
>> in comparation to dump. In some situations this
>> may end in restore fail as there is no enough
>> memory in memory cgroup of on node.
>>
>> The patch fixes the problem by introducing
>> task-measured service_fd_base. It's calculated
>> in dependence of max used file fd and is placed
>> near the right border of kernel-allocated memory
>> hunk for task's fds (see alloc_fdtable() for
>> details). This reduces kernel-allocated files_struct
>> to 512 fds for the most process in standard linux
>> system (I've analysed the processes in my work system).
>>
>> Also, since the "standard processes" will have the same
>> service_fd_base, clone_service_fd() won't have to
>> actualy dup() their service fds for them like we
>> have at the moment. This is the one of reasons why
>> we still keep service fds as a range of fds,
>> and do not try to use unused holes in task fds.
>>
>> Signed-off-by: Kirill Tkhai <ktkhai at virtuozzo.com>
>>
>> v2: Add a handle for very big fd numbers near service_fd_rlim_cur.
>> ---
>> criu/util.c | 57 +++++++++++++++++++++++++++++++++++++++++++++++++++++----
>> 1 file changed, 53 insertions(+), 4 deletions(-)
>>
>> diff --git a/criu/util.c b/criu/util.c
>> index d45bb7d61..8a25ab2cf 100644
>> --- a/criu/util.c
>> +++ b/criu/util.c
>> @@ -527,7 +527,7 @@ int close_service_fd(enum sfd_type type)
>> static void move_service_fd(struct pstree_item *me, int type, int new_id, int new_base)
>> {
>> int old = get_service_fd(type);
>> - int new = __get_service_fd(type, new_id);
>> + int new = new_base - type - SERVICE_FD_MAX * new_id;
>> int ret;
>>
>> if (old < 0)
>> @@ -540,24 +540,73 @@ static void move_service_fd(struct pstree_item *me, int type, int new_id, int ne
>> close(old);
>> }
>>
>> +static int choose_service_fd_base(struct pstree_item *me)
>> +{
>> + int nr, 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;
>> + }
>> + /* 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);
>> + /*
>> + * Service fds go after max fd near right border of alignment:
>> + *
>> + * ...|max_fd|max_fd+1|...|sfd first|...|sfd last (aligned)|
>> + *
>> + * So, they take maximum numbers of area allocated by kernel.
>> + * See linux alloc_fdtable() for details.
>> + */
>> + nr += (SERVICE_FD_MAX - SERVICE_FD_MIN) * fdt_nr;
>> + nr += 16; /* Safety pad */
>> + real_nr = nr;
>> +
>> + nr /= (1024 / sizeof(void *));
>> + nr = 1 << (32 - __builtin_clz(nr + 1));
>> + nr *= (1024 / sizeof(void *));
>> +
>> + if (nr > service_fd_rlim_cur) {
>> + /* Right border is bigger, than rlim. OK, then just aligned value is enough */
>> + nr = round_down(service_fd_rlim_cur, (1024 / sizeof(void *)));
>> + if (nr < real_nr) {
>> + pr_err("Can't chose service_fd_base: %d %d\n", nr, real_nr);
>> + return -1;
>> + }
>> + }
>> +
>> + return nr;
>> +}
>> +
>> int clone_service_fd(struct pstree_item *me)
>> {
>> int id, new_base, i, ret = -1;
>>
>> - new_base = service_fd_base;
>> + new_base = choose_service_fd_base(me);
>> id = rsti(me)->service_fd_id;
>>
>> - if (service_fd_id == id)
>> + if (new_base == -1)
>> + return -1;
>> + if (service_fd_base == new_base && service_fd_id == id)
>> return 0;
>
> For the root process, service_fd_base is changed 1048576 -> 256 and
> there is one service fd, so for the root process fdtable will be
> bigger than it has to be. Actually we have a problem each time when
> a child process has a smaller fdtable than a parent process.
It's because of process's fds are read in root_prepare_shared()->prepare_fd_pid().
This is the reason, why I moved setup_newborn_fds() in "files: Do setup_newborn_fds() later".
It seems this was made to finish CR_STATE_PREPARE_NAMESPACES stage faster (it's being finished
before root_prepare_shared()), because it's important
> And here is a test which shows this problem with more collors
> t a/test/zdtm/static/env00.c b/test/zdtm/static/env00.c
> index 1feabfa9f..2505cb54c 100644
> --- a/test/zdtm/static/env00.c
> +++ b/test/zdtm/static/env00.c
> @@ -1,6 +1,7 @@
> #include <errno.h>
> #include <stdlib.h>
> #include <string.h>
> +#include <sched.h>
>
> #include "zdtmtst.h"
>
> @@ -13,9 +14,22 @@ TEST_OPTION(envname, string, "environment variable name", 1);
> int main(int argc, char **argv)
> {
> char *env;
> + int i;
> + pid_t pid;
>
> test_init(argc, argv);
>
> + for (i = 0; i < 10; i++) {
> + pid = fork();
> + if (pid == 0) {
> + while (1)
> + sleep(1);
> + return 0;
> + }
> + }
> +
> + dup2(1, 1000000);
> +
> if (setenv(envname, test_author, 1)) {
> pr_perror("Can't set env var \"%s\" to \"%s\"", envname, test_author);
> exit(1);
>
> before dump:
> [root at fc24 criu]# echo $((`cat /sys/fs/cgroup/memory/test/memory.kmem.usage_in_bytes` >> 10))
> 12276
>
> after restore:
> [root at fc24 criu]# echo $((`cat /sys/fs/cgroup/memory/test/memory.kmem.usage_in_bytes` >> 10))
> 108432
It's not not obligatory connected with sfds. It's very difficult to measure the memory
connected with file table only. See below:
diff --git a/test/zdtm/static/env00.c b/test/zdtm/static/env00.c
index 1feabfa9f..d2517b835 100644
--- a/test/zdtm/static/env00.c
+++ b/test/zdtm/static/env00.c
@@ -12,10 +12,23 @@ TEST_OPTION(envname, string, "environment variable name", 1);
int main(int argc, char **argv)
{
+ int i;
+ pid_t pid;
char *env;
test_init(argc, argv);
+ for (i = 0; i < 10; i++) {
+ pid = fork();
+ if (pid == 0) {
+ while (1)
+ sleep(1);
+ return 0;
+ }
+ }
+
+// dup2(1, 1000000);
+
if (setenv(envname, test_author, 1)) {
pr_perror("Can't set env var \"%s\" to \"%s\"", envname, test_author);
exit(1);
before dump:
root at pro:/home/kirill# cat /sys/fs/cgroup/memory/test/memory.kmem.usage_in_bytes
11849728
after restore:
root at pro:/home/kirill# cat /sys/fs/cgroup/memory/test/memory.kmem.usage_in_bytes
20877312
Criu restore changes many in-kernel structures, and this is a global problem, not
about sfds.
>>
>> /* Dup sfds in memmove() style: they may overlap */
>> - if (get_service_fd(LOG_FD_OFF) > __get_service_fd(LOG_FD_OFF, id))
>> + if (get_service_fd(LOG_FD_OFF) > new_base - LOG_FD_OFF - SERVICE_FD_MAX * id)
>> for (i = SERVICE_FD_MIN + 1; i < SERVICE_FD_MAX; i++)
>> move_service_fd(me, i, id, new_base);
>> else
>> for (i = SERVICE_FD_MAX - 1; i > SERVICE_FD_MIN; i--)
>> move_service_fd(me, i, id, new_base);
>>
>> + service_fd_base = new_base;
>> service_fd_id = id;
>> ret = 0;
Kirill
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