Wei Liu
2013-Jan-09 09:50 UTC
[PATCH V6] Switch from select() to poll() in xenconsoled''s IO loop
In Linux select() typically supports up to 1024 file descriptors. This can be
a problem when user tries to boot up many guests. Switching to poll() has
minimum impact on existing code and has better scalibility.
pollfd array is dynamically allocated / reallocated. If the array fails to
expand, we just ignore the incoming fd.
Change from V2:
* remove unnecessary malloc in initialize_pollfd_arrays
* use ROUND_UP to get new size of arrays
Change from V3:
* remove initialize and destroy function for array
* embedded tracking structure in struct domain, eliminate fd_to_pollfd
Change from V4:
* make xs_pollfd local to io.c
* add back the 5 ms fuzz
* handle POLLERR and POLLHUP
* treat POLLPRI as error if set in revents
* abort if xenconsoled''s own fds get screwed
* handle broken tty if tty''s fds get screwed
Change from V5:
* make some handles local to handle_io
* remove redundant xc interface
Signed-off-by: Wei Liu <wei.liu2@citrix.com>
---
tools/console/daemon/io.c | 209 +++++++++++++++++++++++++++++----------------
1 file changed, 136 insertions(+), 73 deletions(-)
diff --git a/tools/console/daemon/io.c b/tools/console/daemon/io.c
index 48fe151..6762cba 100644
--- a/tools/console/daemon/io.c
+++ b/tools/console/daemon/io.c
@@ -28,7 +28,7 @@
#include <stdlib.h>
#include <errno.h>
#include <string.h>
-#include <sys/select.h>
+#include <poll.h>
#include <fcntl.h>
#include <unistd.h>
#include <termios.h>
@@ -66,9 +66,12 @@ extern int discard_overflowed_data;
static int log_time_hv_needts = 1;
static int log_time_guest_needts = 1;
static int log_hv_fd = -1;
-static evtchn_port_or_error_t log_hv_evtchn = -1;
-static xc_interface *xch; /* why does xenconsoled have two xc handles ? */
-static xc_evtchn *xce_handle = NULL;
+
+static struct pollfd *fds;
+static unsigned int current_array_size;
+static unsigned int nr_fds;
+
+#define ROUNDUP(_x,_w) (((unsigned long)(_x)+(1UL<<(_w))-1) &
~((1UL<<(_w))-1))
struct buffer {
char *data;
@@ -81,7 +84,9 @@ struct buffer {
struct domain {
int domid;
int master_fd;
+ struct pollfd *master_pollfd;
int slave_fd;
+ struct pollfd *slave_pollfd;
int log_fd;
bool is_dead;
unsigned last_seen;
@@ -92,6 +97,7 @@ struct domain {
evtchn_port_or_error_t local_port;
evtchn_port_or_error_t remote_port;
xc_evtchn *xce_handle;
+ struct pollfd *xce_pollfd;
struct xencons_interface *interface;
int event_count;
long long next_period;
@@ -769,6 +775,17 @@ static int ring_free_bytes(struct domain *dom)
return (sizeof(intf->in) - space);
}
+static void domain_handle_broken_tty(struct domain *dom, int recreate)
+{
+ domain_close_tty(dom);
+
+ if (recreate) {
+ domain_create_tty(dom);
+ } else {
+ shutdown_domain(dom);
+ }
+}
+
static void handle_tty_read(struct domain *dom)
{
ssize_t len = 0;
@@ -794,13 +811,7 @@ static void handle_tty_read(struct domain *dom)
* keep the slave open for the duration.
*/
if (len < 0) {
- domain_close_tty(dom);
-
- if (domain_is_valid(dom->domid)) {
- domain_create_tty(dom);
- } else {
- shutdown_domain(dom);
- }
+ domain_handle_broken_tty(dom, domain_is_valid(dom->domid));
} else if (domain_is_valid(dom->domid)) {
prod = intf->in_prod;
for (i = 0; i < len; i++) {
@@ -828,14 +839,7 @@ static void handle_tty_write(struct domain *dom)
if (len < 1) {
dolog(LOG_DEBUG, "Write failed on domain %d: %zd, %d\n",
dom->domid, len, errno);
-
- domain_close_tty(dom);
-
- if (domain_is_valid(dom->domid)) {
- domain_create_tty(dom);
- } else {
- shutdown_domain(dom);
- }
+ domain_handle_broken_tty(dom, domain_is_valid(dom->domid));
} else {
buffer_advance(&dom->buffer, len);
}
@@ -883,7 +887,7 @@ static void handle_xs(void)
free(vec);
}
-static void handle_hv_logs(void)
+static void handle_hv_logs(xc_evtchn *xce_handle)
{
char buffer[1024*16];
char *bufptr = buffer;
@@ -894,7 +898,7 @@ static void handle_hv_logs(void)
if ((port = xc_evtchn_pending(xce_handle)) == -1)
return;
- if (xc_readconsolering(xch, bufptr, &size, 0, 1, &index) == 0
&& size > 0) {
+ if (xc_readconsolering(xc, bufptr, &size, 0, 1, &index) == 0
&& size > 0) {
int logret;
if (log_time_hv)
logret = write_with_timestamp(log_hv_fd, buffer, size,
@@ -928,18 +932,54 @@ static void handle_log_reload(void)
}
}
+static struct pollfd *set_fds(int fd, short events)
+{
+ struct pollfd *ret;
+ if (current_array_size < nr_fds + 1) {
+ struct pollfd *new_fds = NULL;
+ unsigned long newsize;
+
+ /* Round up to 2^8 boundary, in practice this just
+ * make newsize larger than current_array_size.
+ */
+ newsize = ROUNDUP(nr_fds + 1, 8);
+
+ new_fds = realloc(fds, sizeof(struct pollfd)*newsize);
+ if (!new_fds)
+ goto fail;
+ fds = new_fds;
+
+ memset(&fds[0] + current_array_size, 0,
+ sizeof(struct pollfd) * (newsize-current_array_size));
+ current_array_size = newsize;
+ }
+
+ fds[nr_fds].fd = fd;
+ fds[nr_fds].events = events;
+ ret = &fds[nr_fds];
+ nr_fds++;
+
+ return ret;
+fail:
+ dolog(LOG_ERR, "realloc failed, ignoring fd %d\n", fd);
+ return NULL;
+}
+
+static void reset_fds(void)
+{
+ nr_fds = 0;
+ memset(fds, 0, sizeof(struct pollfd) * current_array_size);
+}
+
void handle_io(void)
{
- fd_set readfds, writefds;
int ret;
+ evtchn_port_or_error_t log_hv_evtchn = -1;
+ struct pollfd *xce_pollfd = NULL;
+ struct pollfd *xs_pollfd = NULL;
+ xc_evtchn *xce_handle = NULL;
if (log_hv) {
- xch = xc_interface_open(0,0,0);
- if (!xch) {
- dolog(LOG_ERR, "Failed to open xc handle: %d (%s)",
- errno, strerror(errno));
- goto out;
- }
xce_handle = xc_evtchn_open(NULL, 0);
if (xce_handle == NULL) {
dolog(LOG_ERR, "Failed to open xce handle: %d (%s)",
@@ -959,21 +999,17 @@ void handle_io(void)
for (;;) {
struct domain *d, *n;
- int max_fd = -1;
- struct timeval timeout;
+ int poll_timeout; /* timeout in milliseconds */
struct timespec ts;
long long now, next_timeout = 0;
- FD_ZERO(&readfds);
- FD_ZERO(&writefds);
+ reset_fds();
- FD_SET(xs_fileno(xs), &readfds);
- max_fd = MAX(xs_fileno(xs), max_fd);
+ xs_pollfd = set_fds(xs_fileno(xs), POLLIN|POLLPRI);
- if (log_hv) {
- FD_SET(xc_evtchn_fd(xce_handle), &readfds);
- max_fd = MAX(xc_evtchn_fd(xce_handle), max_fd);
- }
+ if (log_hv)
+ xce_pollfd = set_fds(xc_evtchn_fd(xce_handle),
+ POLLIN|POLLPRI);
if (clock_gettime(CLOCK_MONOTONIC, &ts) < 0)
return;
@@ -982,10 +1018,12 @@ void handle_io(void)
/* Re-calculate any event counter allowances & unblock
domains with new allowance */
for (d = dom_head; d; d = d->next) {
- /* Add 5ms of fuzz since select() often returns
- a couple of ms sooner than requested. Without
- the fuzz we typically do an extra spin in select()
- with a 1/2 ms timeout every other iteration */
+ /* CS 16257:955ee4fa1345 introduces a 5ms fuzz
+ * for select(), it is not clear poll() has
+ * similar behavior (returning a couple of ms
+ * sooner than requested) as well. Just leave
+ * the fuzz here. Remove it with a separate
+ * patch if necessary */
if ((now+5) > d->next_period) {
d->next_period = now + RATE_LIMIT_PERIOD;
if (d->event_count >= RATE_LIMIT_ALLOWANCE) {
@@ -1006,75 +1044,101 @@ void handle_io(void)
!d->buffer.max_capacity ||
d->buffer.size < d->buffer.max_capacity) {
int evtchn_fd = xc_evtchn_fd(d->xce_handle);
- FD_SET(evtchn_fd, &readfds);
- max_fd = MAX(evtchn_fd, max_fd);
+ d->xce_pollfd = set_fds(evtchn_fd,
+ POLLIN|POLLPRI);
}
}
if (d->master_fd != -1) {
+ short events = 0;
if (!d->is_dead && ring_free_bytes(d))
- FD_SET(d->master_fd, &readfds);
+ events |= POLLIN;
if (!buffer_empty(&d->buffer))
- FD_SET(d->master_fd, &writefds);
- max_fd = MAX(d->master_fd, max_fd);
+ events |= POLLOUT;
+
+ if (events)
+ d->master_pollfd + set_fds(d->master_fd,
+ events|POLLPRI);
}
}
/* If any domain has been rate limited, we need to work
- out what timeout to supply to select */
+ out what timeout to supply to poll */
if (next_timeout) {
long long duration = (next_timeout - now);
if (duration <= 0) /* sanity check */
duration = 1;
- timeout.tv_sec = duration / 1000;
- timeout.tv_usec = ((duration - (timeout.tv_sec * 1000))
- * 1000);
+ poll_timeout = (int)duration;
}
- ret = select(max_fd + 1, &readfds, &writefds, 0,
- next_timeout ? &timeout : NULL);
+ ret = poll(fds, nr_fds, next_timeout ? poll_timeout : -1);
if (log_reload) {
handle_log_reload();
log_reload = 0;
}
- /* Abort if select failed, except for EINTR cases
+ /* Abort if poll failed, except for EINTR cases
which indicate a possible log reload */
if (ret == -1) {
if (errno == EINTR)
continue;
- dolog(LOG_ERR, "Failure in select: %d (%s)",
+ dolog(LOG_ERR, "Failure in poll: %d (%s)",
errno, strerror(errno));
break;
}
- if (log_hv && FD_ISSET(xc_evtchn_fd(xce_handle), &readfds))
- handle_hv_logs();
+ if (log_hv && xce_pollfd) {
+ if (xce_pollfd->revents & ~(POLLIN|POLLOUT|POLLPRI)) {
+ dolog(LOG_ERR,
+ "Failure in poll xce_handle: %d (%s)",
+ errno, strerror(errno));
+ break;
+ } else if (xce_pollfd->revents & POLLIN)
+ handle_hv_logs(xce_handle);
+ }
if (ret <= 0)
continue;
- if (FD_ISSET(xs_fileno(xs), &readfds))
- handle_xs();
+ if (xs_pollfd) {
+ if (xs_pollfd->revents & ~(POLLIN|POLLOUT|POLLPRI)) {
+ dolog(LOG_ERR,
+ "Failure in poll xs_handle: %d (%s)",
+ errno, strerror(errno));
+ break;
+ } else if (xs_pollfd->revents & POLLIN)
+ handle_xs();
+ }
for (d = dom_head; d; d = n) {
n = d->next;
if (d->event_count < RATE_LIMIT_ALLOWANCE) {
if (d->xce_handle != NULL &&
- FD_ISSET(xc_evtchn_fd(d->xce_handle),
- &readfds))
- handle_ring_read(d);
+ d->xce_pollfd &&
+ !(d->xce_pollfd->revents &
+ ~(POLLIN|POLLOUT|POLLPRI)) &&
+ (d->xce_pollfd->revents &
+ POLLIN))
+ handle_ring_read(d);
}
- if (d->master_fd != -1 && FD_ISSET(d->master_fd,
- &readfds))
- handle_tty_read(d);
-
- if (d->master_fd != -1 && FD_ISSET(d->master_fd,
- &writefds))
- handle_tty_write(d);
+ if (d->master_fd != -1 && d->master_pollfd) {
+ if (d->master_pollfd->revents &
+ ~(POLLIN|POLLOUT|POLLPRI))
+ domain_handle_broken_tty(d,
+ domain_is_valid(d->domid));
+ else {
+ if (d->master_pollfd->revents &
+ POLLIN)
+ handle_tty_read(d);
+ if (d->master_pollfd->revents &
+ POLLOUT)
+ handle_tty_write(d);
+ }
+ }
if (d->last_seen != enum_pass)
shutdown_domain(d);
@@ -1084,15 +1148,14 @@ void handle_io(void)
}
}
+ free(fds);
+ current_array_size = 0;
+
out:
if (log_hv_fd != -1) {
close(log_hv_fd);
log_hv_fd = -1;
}
- if (xch) {
- xc_interface_close(xch);
- xch = 0;
- }
if (xce_handle != NULL) {
xc_evtchn_close(xce_handle);
xce_handle = NULL;
--
1.7.10.4
Ian Campbell
2013-Jan-09 11:02 UTC
Re: [PATCH V6] Switch from select() to poll() in xenconsoled''s IO loop
On Wed, 2013-01-09 at 09:50 +0000, Wei Liu wrote:> In Linux select() typically supports up to 1024 file descriptors. This can be > a problem when user tries to boot up many guests. Switching to poll() has > minimum impact on existing code and has better scalibility. > > pollfd array is dynamically allocated / reallocated. If the array fails to > expand, we just ignore the incoming fd. > > Change from V2: > * remove unnecessary malloc in initialize_pollfd_arrays > * use ROUND_UP to get new size of arrays > > Change from V3: > * remove initialize and destroy function for array > * embedded tracking structure in struct domain, eliminate fd_to_pollfd > > Change from V4: > * make xs_pollfd local to io.c > * add back the 5 ms fuzz > * handle POLLERR and POLLHUP > * treat POLLPRI as error if set in revents > * abort if xenconsoled''s own fds get screwed > * handle broken tty if tty''s fds get screwed > > Change from V5: > * make some handles local to handle_ioThe code now resets some of these to -1/NULL on exit from handle_io, which isn''t really necessary but I''m not to bothered about that.> * remove redundant xc interface > > Signed-off-by: Wei Liu <wei.liu2@citrix.com>Acked-by: Ian Campbell <ian.campbell@citrix.com>
Ian Campbell
2013-Jan-11 12:25 UTC
Re: [PATCH V6] Switch from select() to poll() in xenconsoled''s IO loop
On Wed, 2013-01-09 at 11:02 +0000, Ian Campbell wrote:> On Wed, 2013-01-09 at 09:50 +0000, Wei Liu wrote: > > In Linux select() typically supports up to 1024 file descriptors. This can be > > a problem when user tries to boot up many guests. Switching to poll() has > > minimum impact on existing code and has better scalibility. > > > > pollfd array is dynamically allocated / reallocated. If the array fails to > > expand, we just ignore the incoming fd.> Acked-by: Ian Campbell <ian.campbell@citrix.com>And now applied. Ian.
Ian Campbell
2013-Jan-13 10:24 UTC
Re: [PATCH V6] Switch from select() to poll() in xenconsoled''s IO loop
On Fri, 2013-01-11 at 12:25 +0000, Ian Campbell wrote:> On Wed, 2013-01-09 at 11:02 +0000, Ian Campbell wrote: > > On Wed, 2013-01-09 at 09:50 +0000, Wei Liu wrote: > > > In Linux select() typically supports up to 1024 file descriptors. This can be > > > a problem when user tries to boot up many guests. Switching to poll() has > > > minimum impact on existing code and has better scalibility. > > > > > > pollfd array is dynamically allocated / reallocated. If the array fails to > > > expand, we just ignore the incoming fd. > > > Acked-by: Ian Campbell <ian.campbell@citrix.com> > > And now applied.I''m afraid I''ve now reverted this, the bisector <E1Tu7of-0004FF-Mf@woking.cam.xci-test.com> fingered it as responsible for the failures in test flight 14869 onwards. Ian.