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/*
* xen-lowmemd: demo VIRQ_ENOMEM
* Andres Lagar-Cavilla (GridCentric Inc.)
*/
#include <stdio.h>
#include <xenctrl.h>
#include <xenstore.h>
#include <stdlib.h>
#include <string.h>
static evtchn_port_t virq_port = -1;
static xc_evtchn *xce_handle = NULL;
static xc_interface *xch = NULL;
static struct xs_handle *xs_handle = NULL;
void cleanup(void)
{
if (virq_port > -1)
xc_evtchn_unbind(xce_handle, virq_port);
if (xce_handle)
xc_evtchn_close(xce_handle);
if (xch)
xc_interface_close(xch);
if (xs_handle)
xs_daemon_close(xs_handle);
}
/* Never shrink dom0 below 1 GiB */
#define DOM0_FLOOR (1 << 30)
#define DOM0_FLOOR_PG ((DOM0_FLOOR) >> 12)
/* Act if free memory is less than 92 MiB */
#define THRESHOLD (92 << 20)
#define THRESHOLD_PG ((THRESHOLD) >> 12)
#define BUFSZ 512
void handle_low_mem(void)
{
xc_dominfo_t dom0_info;
xc_physinfo_t info;
unsigned long long free_pages, dom0_pages, diff, dom0_target;
char data[BUFSZ], error[BUFSZ];
if (xc_physinfo(xch, &info) < 0)
{
perror("Getting physinfo failed");
return;
}
free_pages = (unsigned long long) info.free_pages;
printf("Available free pages: 0x%llx:%llux\n",
free_pages, free_pages);
/* Don't do anything if we have more than the threshold free */
if ( free_pages >= THRESHOLD_PG )
return;
diff = THRESHOLD_PG - free_pages;
if (xc_domain_getinfo(xch, 0, 1, &dom0_info) < 1)
{
perror("Failed to get dom0 info");
return;
}
dom0_pages = (unsigned long long) dom0_info.nr_pages;
printf("Dom0 pages: 0x%llx:%llu\n", dom0_pages, dom0_pages);
dom0_target = dom0_pages - diff;
if (dom0_target <= DOM0_FLOOR_PG)
return;
printf("Shooting for dom0 target 0x%llx:%llu\n",
dom0_target, dom0_target);
snprintf(data, BUFSZ, "%llu", dom0_target);
if (!xs_write(xs_handle, XBT_NULL,
"/local/domain/0/memory/target", data, strlen(data)))
{
snprintf(error, BUFSZ,"Failed to write target %s to xenstore", data);
perror(error);
}
}
int main(int argc, char *argv[])
{
int rc;
atexit(cleanup);
xch = xc_interface_open(NULL, NULL, 0);
if (xch == NULL)
{
perror("Failed to open xc interface");
return 1;
}
xce_handle = xc_evtchn_open(NULL, 0);
if (xce_handle == NULL)
{
perror("Failed to open evtchn device");
return 2;
}
xs_handle = xs_daemon_open();
if (xs_handle == NULL)
{
perror("Failed to open xenstore connection");
return 3;
}
if ((rc = xc_evtchn_bind_virq(xce_handle, VIRQ_ENOMEM)) == -1)
{
perror("Failed to bind to domain exception virq port");
return 4;
}
virq_port = rc;
while(1)
{
evtchn_port_t port;
if ((port = xc_evtchn_pending(xce_handle)) == -1)
{
perror("Failed to listen for pending event channel");
return 5;
}
if (port != virq_port)
{
char data[BUFSZ];
snprintf(data, BUFSZ, "Wrong port, got %d expected %d", port, virq_port);
perror(data);
return 6;
}
if (xc_evtchn_unmask(xce_handle, port) == -1)
{
perror("Failed to unmask port");
return 7;
}
printf("Got a virq kick, time to get work\n");
handle_low_mem();
}
return 0;
}
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