From mboxrd@z Thu Jan 1 00:00:00 1970 From: Wei Liu Subject: Re: [PATCH v2] tools/xenconsoled: Increase file descriptor limit Date: Tue, 17 Feb 2015 16:28:32 +0000 Message-ID: <20150217162831.GH2159@zion.uk.xensource.com> References: <1424190084-9922-1-git-send-email-andrew.cooper3@citrix.com> Mime-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Return-path: Content-Disposition: inline In-Reply-To: <1424190084-9922-1-git-send-email-andrew.cooper3@citrix.com> List-Unsubscribe: , List-Post: List-Help: List-Subscribe: , Sender: xen-devel-bounces@lists.xen.org Errors-To: xen-devel-bounces@lists.xen.org To: Andrew Cooper Cc: Wei Liu , Ian Jackson , Ian Campbell , Xen-devel List-Id: xen-devel@lists.xenproject.org On Tue, Feb 17, 2015 at 04:21:24PM +0000, 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 > CC: Ian Campbell > CC: Ian Jackson > CC: Wei Liu > > --- > v2: > * Always increase soft limit to hard limit > * Correct commment regarding number of file descriptors > * long -> unsigned long as that appears to be the underlying type of an rlim_t > --- > tools/console/daemon/main.c | 45 +++++++++++++++++++++++++++++++++++++++++++ > 1 file changed, 45 insertions(+) > > diff --git a/tools/console/daemon/main.c b/tools/console/daemon/main.c > index 92d2fc4..0bb9d8a 100644 > --- a/tools/console/daemon/main.c > +++ b/tools/console/daemon/main.c > @@ -26,6 +26,7 @@ > #include > #include > #include > +#include > > #include "xenctrl.h" > > @@ -55,6 +56,48 @@ static void version(char *name) > printf("Xen Console Daemon 3.0\n"); > } > > +/* > + * Xenconsoled requires two file descriptors for each PV console (pty and log > + * file), 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; > + unsigned long nr_open = 4096; > + > + if (getrlimit(RLIMIT_NOFILE, &lim) < 0) > + return; > + > + /* Increase the soft limit to the current hard limit. */ > + if (lim.rlim_cur < lim.rlim_max) { > + lim.rlim_cur = lim.rlim_max; > + if (setrlimit(RLIMIT_NOFILE, &lim) < 0) > + return; > + } > + > + /* Attempt to locate the system maximum. */ > + fs_nr_open = fopen("/proc/sys/fs/nr_open", "r"); > + if (fs_nr_open) { > + unsigned long nr; > + > + if (fscanf(fs_nr_open, "%lu", &nr) == 1) > + nr_open = nr; > + fclose(fs_nr_open); > + } > + > + /* > + * In the likely case that we are a root process with > + * CAP_SYS_RESOURCE, attempt to up our hard limit. > + */ > + if (nr_open > lim.rlim_max) { > + lim.rlim_cur = lim.rlim_max = nr_open; > + setrlimit(RLIMIT_NOFILE, &lim); > + } > +} > + This function looks Linux centric (/proc and CAP_SYSRESOURCE). Please be considerate to other Unices. :-) Also you might want to log failures along the line. Wei. > int main(int argc, char **argv) > { > const char *sopts = "hVvit:o:"; > @@ -154,6 +197,8 @@ 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