* [PATCH] tools/xenconsoled: Increase file descriptor limit
@ 2015-02-16 18:17 Andrew Cooper
2015-02-16 20:44 ` Don Slutz
0 siblings, 1 reply; 3+ messages in thread
From: Andrew Cooper @ 2015-02-16 18:17 UTC (permalink / raw)
To: Xen-devel; +Cc: Andrew Cooper, Ian Jackson, Ian Campbell, Wei Liu
XenServer's VM density testing uncovered a regression when moving from
sysvinit to systemd where the file descriptor limit dropped from 4096 to
1024. (XenServer had previously inserted a ulimit statement into its
initscripts.)
One solution is to use LimitNOFILE=4096 in xenconsoled.service to match the
lost ulimit, but that is only a stopgap solution.
As Xenconsoled genuinely needs a large number of file descriptors if a large
number of domains are running, and is well behaved with its descriptors,
attempt to up the limit to the system maximum.
Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
CC: Ian Campbell <Ian.Campbell@citrix.com>
CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
CC: Wei Liu <wei.liu2@citrix.com>
---
tools/console/daemon/main.c | 31 +++++++++++++++++++++++++++++++
1 file changed, 31 insertions(+)
diff --git a/tools/console/daemon/main.c b/tools/console/daemon/main.c
index 92d2fc4..759c061 100644
--- a/tools/console/daemon/main.c
+++ b/tools/console/daemon/main.c
@@ -26,6 +26,7 @@
#include <string.h>
#include <signal.h>
#include <sys/types.h>
+#include <sys/resource.h>
#include "xenctrl.h"
@@ -55,6 +56,34 @@ static void version(char *name)
printf("Xen Console Daemon 3.0\n");
}
+/*
+ * Xenconsoled requires one file descriptor for each PV console, which can
+ * easily exceed the default of 1024 if many guests are running. Try to set
+ * the fd limit to the system maximum, falling back to a default of 4096.
+ */
+static void increase_fd_limit(void)
+{
+ FILE *fs_nr_open;
+ struct rlimit lim;
+ long nr_open = 4096;
+ int rc;
+
+ rc = getrlimit(RLIMIT_NOFILE, &lim);
+ if (rc)
+ return;
+
+ fs_nr_open = fopen("/proc/sys/fs/nr_open", "r");
+ if (fs_nr_open) {
+ fscanf(fs_nr_open, "%ld", &nr_open);
+ fclose(fs_nr_open);
+ }
+
+ if ((nr_open > lim.rlim_cur) || (nr_open > lim.rlim_max)) {
+ lim.rlim_cur = lim.rlim_max = nr_open;
+ setrlimit(RLIMIT_NOFILE, &lim);
+ }
+}
+
int main(int argc, char **argv)
{
const char *sopts = "hVvit:o:";
@@ -154,6 +183,8 @@ int main(int argc, char **argv)
openlog("xenconsoled", syslog_option, LOG_DAEMON);
setlogmask(syslog_mask);
+ increase_fd_limit();
+
if (!is_interactive) {
daemonize(pidfile ? pidfile : "/var/run/xenconsoled.pid");
}
--
1.7.10.4
^ permalink raw reply related [flat|nested] 3+ messages in thread
* Re: [PATCH] tools/xenconsoled: Increase file descriptor limit
2015-02-16 18:17 [PATCH] tools/xenconsoled: Increase file descriptor limit Andrew Cooper
@ 2015-02-16 20:44 ` Don Slutz
2015-02-17 9:07 ` Andrew Cooper
0 siblings, 1 reply; 3+ messages in thread
From: Don Slutz @ 2015-02-16 20:44 UTC (permalink / raw)
To: Andrew Cooper, Xen-devel; +Cc: Wei Liu, Ian Jackson, Ian Campbell
On 02/16/15 13:17, Andrew Cooper wrote:
> XenServer's VM density testing uncovered a regression when moving from
> sysvinit to systemd where the file descriptor limit dropped from 4096 to
> 1024. (XenServer had previously inserted a ulimit statement into its
> initscripts.)
>
> One solution is to use LimitNOFILE=4096 in xenconsoled.service to match the
> lost ulimit, but that is only a stopgap solution.
>
> As Xenconsoled genuinely needs a large number of file descriptors if a large
> number of domains are running, and is well behaved with its descriptors,
> attempt to up the limit to the system maximum.
>
> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
> CC: Ian Campbell <Ian.Campbell@citrix.com>
> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
> CC: Wei Liu <wei.liu2@citrix.com>
> ---
> tools/console/daemon/main.c | 31 +++++++++++++++++++++++++++++++
> 1 file changed, 31 insertions(+)
>
> diff --git a/tools/console/daemon/main.c b/tools/console/daemon/main.c
> index 92d2fc4..759c061 100644
> --- a/tools/console/daemon/main.c
> +++ b/tools/console/daemon/main.c
> @@ -26,6 +26,7 @@
> #include <string.h>
> #include <signal.h>
> #include <sys/types.h>
> +#include <sys/resource.h>
>
> #include "xenctrl.h"
>
> @@ -55,6 +56,34 @@ static void version(char *name)
> printf("Xen Console Daemon 3.0\n");
> }
>
> +/*
> + * Xenconsoled requires one file descriptor for each PV console, which can
> + * easily exceed the default of 1024 if many guests are running. Try to set
> + * the fd limit to the system maximum, falling back to a default of 4096.
> + */
> +static void increase_fd_limit(void)
> +{
> + FILE *fs_nr_open;
> + struct rlimit lim;
> + long nr_open = 4096;
> + int rc;
> +
> + rc = getrlimit(RLIMIT_NOFILE, &lim);
> + if (rc)
> + return;
> +
> + fs_nr_open = fopen("/proc/sys/fs/nr_open", "r");
> + if (fs_nr_open) {
> + fscanf(fs_nr_open, "%ld", &nr_open);
> + fclose(fs_nr_open);
> + }
> +
> + if ((nr_open > lim.rlim_cur) || (nr_open > lim.rlim_max)) {
> + lim.rlim_cur = lim.rlim_max = nr_open;
> + setrlimit(RLIMIT_NOFILE, &lim);
> + }
> +}
> +
I am not sure that Xenconsoled is required to have the CAP_SYS_RESOURCE
capability. With out this, the "soft" (rlim_cur) will most like not be
changed. Does it make sense to include:
lim.rlim_cur = lim.rlim_max;
rc = setrlimit(RLIMIT_NOFILE, &lim);
if (rc)
return;
before "fs_nr_open = fopen(..."?
-Don Slutz
> int main(int argc, char **argv)
> {
> const char *sopts = "hVvit:o:";
> @@ -154,6 +183,8 @@ int main(int argc, char **argv)
> openlog("xenconsoled", syslog_option, LOG_DAEMON);
> setlogmask(syslog_mask);
>
> + increase_fd_limit();
> +
> if (!is_interactive) {
> daemonize(pidfile ? pidfile : "/var/run/xenconsoled.pid");
> }
>
^ permalink raw reply [flat|nested] 3+ messages in thread
* Re: [PATCH] tools/xenconsoled: Increase file descriptor limit
2015-02-16 20:44 ` Don Slutz
@ 2015-02-17 9:07 ` Andrew Cooper
0 siblings, 0 replies; 3+ messages in thread
From: Andrew Cooper @ 2015-02-17 9:07 UTC (permalink / raw)
To: Don Slutz, Xen-devel; +Cc: Wei Liu, Ian Jackson, Ian Campbell
On 16/02/2015 20:44, Don Slutz wrote:
> On 02/16/15 13:17, Andrew Cooper wrote:
>> XenServer's VM density testing uncovered a regression when moving from
>> sysvinit to systemd where the file descriptor limit dropped from 4096 to
>> 1024. (XenServer had previously inserted a ulimit statement into its
>> initscripts.)
>>
>> One solution is to use LimitNOFILE=4096 in xenconsoled.service to match the
>> lost ulimit, but that is only a stopgap solution.
>>
>> As Xenconsoled genuinely needs a large number of file descriptors if a large
>> number of domains are running, and is well behaved with its descriptors,
>> attempt to up the limit to the system maximum.
>>
>> Signed-off-by: Andrew Cooper <andrew.cooper3@citrix.com>
>> CC: Ian Campbell <Ian.Campbell@citrix.com>
>> CC: Ian Jackson <Ian.Jackson@eu.citrix.com>
>> CC: Wei Liu <wei.liu2@citrix.com>
>> ---
>> tools/console/daemon/main.c | 31 +++++++++++++++++++++++++++++++
>> 1 file changed, 31 insertions(+)
>>
>> diff --git a/tools/console/daemon/main.c b/tools/console/daemon/main.c
>> index 92d2fc4..759c061 100644
>> --- a/tools/console/daemon/main.c
>> +++ b/tools/console/daemon/main.c
>> @@ -26,6 +26,7 @@
>> #include <string.h>
>> #include <signal.h>
>> #include <sys/types.h>
>> +#include <sys/resource.h>
>>
>> #include "xenctrl.h"
>>
>> @@ -55,6 +56,34 @@ static void version(char *name)
>> printf("Xen Console Daemon 3.0\n");
>> }
>>
>> +/*
>> + * Xenconsoled requires one file descriptor for each PV console, which can
>> + * easily exceed the default of 1024 if many guests are running. Try to set
>> + * the fd limit to the system maximum, falling back to a default of 4096.
>> + */
>> +static void increase_fd_limit(void)
>> +{
>> + FILE *fs_nr_open;
>> + struct rlimit lim;
>> + long nr_open = 4096;
>> + int rc;
>> +
>> + rc = getrlimit(RLIMIT_NOFILE, &lim);
>> + if (rc)
>> + return;
>> +
>> + fs_nr_open = fopen("/proc/sys/fs/nr_open", "r");
>> + if (fs_nr_open) {
>> + fscanf(fs_nr_open, "%ld", &nr_open);
>> + fclose(fs_nr_open);
>> + }
>> +
>> + if ((nr_open > lim.rlim_cur) || (nr_open > lim.rlim_max)) {
>> + lim.rlim_cur = lim.rlim_max = nr_open;
>> + setrlimit(RLIMIT_NOFILE, &lim);
>> + }
>> +}
>> +
> I am not sure that Xenconsoled is required to have the CAP_SYS_RESOURCE
> capability. With out this, the "soft" (rlim_cur) will most like not be
> changed. Does it make sense to include:
>
> lim.rlim_cur = lim.rlim_max;
> rc = setrlimit(RLIMIT_NOFILE, &lim);
> if (rc)
> return;
>
> before "fs_nr_open = fopen(..."?
It probably does make sense, although xenconsoled cannot realistically
run without privilege because of privcmd and /dev/ptmx.
I shall respin.
~Andrew
^ permalink raw reply [flat|nested] 3+ messages in thread
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2015-02-16 18:17 [PATCH] tools/xenconsoled: Increase file descriptor limit Andrew Cooper
2015-02-16 20:44 ` Don Slutz
2015-02-17 9:07 ` Andrew Cooper
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