[Xen-devel] [PATCH 9 of 9] xenpaging: watch the domains /xenpaging/num_pages xenstore value

[Olaf Hering <olaf@xxxxxxxxx>]

# HG changeset patch
# User Olaf Hering <olaf@xxxxxxxxx>
# Date 1316067236 -7200
# Node ID ad903b34e0997e864539e36b92dde234f9ffbd55
# Parent  1addb9e81178ea164ef516f340df2607fddcb930
xenpaging: watch the domains /xenpaging/num_pages xenstore value

Subsequent patches will use xenstored to store the numbers of pages
xenpaging is suppose to page-out.
Remove num_pages and use target_pages instead.

Signed-off-by: Olaf Hering <olaf@xxxxxxxxx>

diff -r 1addb9e81178 -r ad903b34e099 tools/xenpaging/policy_default.c
--- a/tools/xenpaging/policy_default.c
+++ b/tools/xenpaging/policy_default.c
@@ -70,7 +70,7 @@ int policy_init(xenpaging_t *paging)
 
     /* Start in the middle to avoid paging during BIOS startup */
     current_gfn = max_pages / 2;
-    current_gfn -= paging->num_pages / 2;
+    current_gfn -= paging->target_pages / 2;
 
     rc = 0;
  out:
diff -r 1addb9e81178 -r ad903b34e099 tools/xenpaging/xenpaging.c
--- a/tools/xenpaging/xenpaging.c
+++ b/tools/xenpaging/xenpaging.c
@@ -35,6 +35,9 @@
 #include "policy.h"
 #include "xenpaging.h"
 
+/* Defines number of pages to page-out */
+#define WATCH_TARGETPAGES "/xenpaging/num_pages"
+static char *watch_targetpages;
 static char watch_token[16];
 static char filename[80];
 static int interrupted;
@@ -72,7 +75,7 @@ static int xenpaging_wait_for_event_or_t
 {
     xc_interface *xch = paging->xc_handle;
     xc_evtchn *xce = paging->mem_event.xce_handle;
-    char **vec;
+    char **vec, *val;
     unsigned int num;
     struct pollfd fd[2];
     int port;
@@ -101,6 +104,7 @@ static int xenpaging_wait_for_event_or_t
         vec = xs_read_watch(paging->xs_handle, &num);
         if ( vec )
         {
+            DPRINTF("path '%s' token '%s'\n", vec[XS_WATCH_PATH], 
vec[XS_WATCH_TOKEN]);
             if ( strcmp(vec[XS_WATCH_PATH], "@releaseDomain") == 0 && 
strcmp(vec[XS_WATCH_TOKEN], watch_token) == 0 )
             {
                 /* If our guest disappeared, set interrupt flag and fall 
through */
@@ -111,6 +115,22 @@ static int xenpaging_wait_for_event_or_t
                     rc = 0;
                 }
             }
+            else if ( strcmp(vec[XS_WATCH_PATH], watch_targetpages) == 0 )
+            {
+                int ret, target_pages;
+                val = xs_read(paging->xs_handle, XBT_NULL, vec[XS_WATCH_PATH], 
NULL);
+                if (val)
+                {
+                    ret = sscanf(val, "%d", &target_pages);
+                    if ( ret > 0 )
+                    {
+                        if ( target_pages < 0 || target_pages > 
paging->max_pages )
+                            target_pages = paging->max_pages;
+                        paging->target_pages = target_pages;
+                        DPRINTF("new target_pages %d\n", target_pages);
+                    }
+                }
+            }
             free(vec);
         }
     }
@@ -167,8 +187,8 @@ static xenpaging_t *xenpaging_init(domid
     xc_domaininfo_t domain_info;
     xc_interface *xch;
     xentoollog_logger *dbg = NULL;
-    char *p;
-    int rc;
+    char *p, *dom_path = NULL, *watchdir = WATCH_TARGETPAGES;
+    int rc, len;
 
     /* Allocate memory */
     paging = calloc(1, sizeof(xenpaging_t));
@@ -201,6 +221,28 @@ static xenpaging_t *xenpaging_init(domid
         goto err;
     }
 
+    /* watch guests xenpaging directory */
+    dom_path = xs_get_domain_path(paging->xs_handle, domain_id);
+    if ( !dom_path )
+    {
+        ERROR("Could not find domain path\n");
+        goto err;
+    }
+    len = strlen(dom_path) + strlen(watchdir) + 1;
+    watch_targetpages = malloc(len);
+    if ( !watch_targetpages )
+    {
+        ERROR("Could not alloc domain path\n");
+        goto err;
+    }
+    snprintf(watch_targetpages, len, "%s%s", dom_path, watchdir);
+    DPRINTF("watching '%s'\n", watch_targetpages);
+    if ( xs_watch(paging->xs_handle, watch_targetpages, "") == false )
+    {
+        ERROR("Could not bind to xenpaging watch\n");
+        goto err;
+    }
+
     p = getenv("XENPAGING_POLICY_MRU_SIZE");
     if ( p && *p )
     {
@@ -299,7 +341,7 @@ static xenpaging_t *xenpaging_init(domid
         num_pages = paging->max_pages;
         DPRINTF("setting num_pages to %d\n", num_pages);
     }
-    paging->num_pages = num_pages;
+    paging->target_pages = num_pages;
 
     /* Initialise policy */
     rc = policy_init(paging);
@@ -330,6 +372,8 @@ static xenpaging_t *xenpaging_init(domid
             free(paging->mem_event.ring_page);
         }
 
+        free(dom_path);
+        free(watch_targetpages);
         free(paging->bitmap);
         free(paging);
     }
@@ -345,6 +389,9 @@ static int xenpaging_teardown(xenpaging_
     if ( paging == NULL )
         return 0;
 
+    xs_unwatch(paging->xs_handle, watch_targetpages, "");
+    xs_unwatch(paging->xs_handle, "@releaseDomain", watch_token);
+
     xch = paging->xc_handle;
     paging->xc_handle = NULL;
     /* Tear down domain paging in Xen */
@@ -649,6 +696,7 @@ int main(int argc, char *argv[])
     xenpaging_victim_t *victims;
     mem_event_request_t req;
     mem_event_response_t rsp;
+    int num, prev_num = 0;
     int i;
     int rc = -1;
     int rc1;
@@ -673,7 +721,7 @@ int main(int argc, char *argv[])
     }
     xch = paging->xc_handle;
 
-    DPRINTF("starting %s %u %d\n", argv[0], paging->mem_event.domain_id, 
paging->num_pages);
+    DPRINTF("starting %s %u %d\n", argv[0], paging->mem_event.domain_id, 
paging->target_pages);
 
     /* Open file */
     sprintf(filename, "page_cache_%u", paging->mem_event.domain_id);
@@ -703,9 +751,6 @@ int main(int argc, char *argv[])
     /* listen for page-in events to stop pager */
     create_page_in_thread(paging);
 
-    i = evict_pages(paging, fd, victims, paging->num_pages);
-    DPRINTF("%d pages evicted. Done.\n", i);
-
     /* Swap pages in and out */
     while ( 1 )
     {
@@ -774,8 +819,6 @@ int main(int argc, char *argv[])
                  * or clear this pagefile slot on exit */
                 if ( interrupted )
                     victims[i].gfn = INVALID_MFN;
-                else
-                    evict_victim(paging, &victims[i], fd, i);
             }
             else
             {
@@ -819,6 +862,29 @@ int main(int argc, char *argv[])
             if ( interrupted )
                 break;
         }
+        if ( paging->num_paged_out < paging->target_pages )
+        {
+            num = paging->target_pages - paging->num_paged_out;
+            if ( num != prev_num )
+            {
+                DPRINTF("Need to evict %d pages to reach %d target_pages\n", 
num, paging->target_pages);
+                prev_num = num;
+            }
+            /* Limit the number of evicts to be able to process page-in 
requests */
+            if ( num > 42 )
+                num = 42;
+            evict_pages(paging, fd, victims, num);
+        }
+        else if ( paging->num_paged_out > paging->target_pages )
+        {
+            num = paging->num_paged_out - paging->target_pages;
+            if ( num != prev_num )
+            {
+                DPRINTF("Need to resume %d pages to reach %d target_pages\n", 
num, paging->target_pages);
+                prev_num = num;
+            }
+            resume_pages(paging, num);
+        }
     }
     DPRINTF("xenpaging got signal %d\n", interrupted);
 
diff -r 1addb9e81178 -r ad903b34e099 tools/xenpaging/xenpaging.h
--- a/tools/xenpaging/xenpaging.h
+++ b/tools/xenpaging/xenpaging.h
@@ -50,7 +50,8 @@ typedef struct xenpaging {
     /* number of pages for which data structures were allocated */
     int max_pages;
     int num_paged_out;
-    int num_pages;
+    /* number of pages xenpaging is supposed to page-out */
+    int target_pages;
     int policy_mru_size;
     unsigned long pagein_queue[XENPAGING_PAGEIN_QUEUE_SIZE];
 } xenpaging_t;

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