libxl: remove freemem_slack

freemem_slack accounts for the amount of memory to be left free in the
system because empirical experiments seem to demonstrate that is needed
for "stability reasons".

As we don't have any actual data on these stability issues, remove it.

Signed-off-by: Stefano Stabellini <stefano.stabellini@eu.citrix.com>
CC: mlatimer@suse.com
CC: ian.campbell@citrix.com
Acked-by: Mike Latimer <mlatimer@suse.com>
Acked-by: Ian Campbell <ian.campbell@citrix.com>

diff --git a/tools/libxl/libxl.c b/tools/libxl/libxl.c
index b9a19413a9e24f4e5149719515473312691fd303..a68f6efb2f38eced907c70b30e4ceba7850ab8f7 100644 (file)
--- a/tools/libxl/libxl.c
+++ b/tools/libxl/libxl.c
@@ -4592,13 +4592,11 @@ static int libxl__fill_dom0_memory_info(libxl__gc *gc, uint32_t *target_memkb,
     int rc;
     libxl_dominfo info;
     libxl_physinfo physinfo;
-    char *target = NULL, *staticmax = NULL, *freememslack = NULL, *endptr = NULL;
+    char *target = NULL, *staticmax = NULL, *endptr = NULL;
     char *target_path = "/local/domain/0/memory/target";
     char *max_path = "/local/domain/0/memory/static-max";
-    char *free_mem_slack_path = "/local/domain/0/memory/freemem-slack";
     xs_transaction_t t;
     libxl_ctx *ctx = libxl__gc_owner(gc);
-    uint32_t free_mem_slack_kb = 0;
 
     libxl_dominfo_init(&info);
 
@@ -4607,8 +4605,7 @@ retry_transaction:
 
     target = libxl__xs_read(gc, t, target_path);
     staticmax = libxl__xs_read(gc, t, max_path);
-    freememslack = libxl__xs_read(gc, t, free_mem_slack_path);
-    if (target && staticmax && freememslack) {
+    if (target && staticmax) {
         rc = 0;
         goto out;
     }
@@ -4655,15 +4652,6 @@ retry_transaction:
         *max_memkb = (uint32_t) info.max_memkb;
     }
 
-    if (freememslack == NULL) {
-        free_mem_slack_kb = (uint32_t) (PAGE_TO_MEMKB(physinfo.total_pages) -
-                info.current_memkb);
-        /* From empirical measurements the free_mem_slack shouldn't be more
-         * than 15% of the total memory present on the system. */
-        if (free_mem_slack_kb > PAGE_TO_MEMKB(physinfo.total_pages) * 0.15)
-            free_mem_slack_kb = PAGE_TO_MEMKB(physinfo.total_pages) * 0.15;
-        libxl__xs_write(gc, t, free_mem_slack_path, "%"PRIu32, free_mem_slack_kb);
-    }
     rc = 0;
 
 out:
@@ -4678,33 +4666,6 @@ out:
     return rc;
 }
 
-/* returns how much memory should be left free in the system */
-static int libxl__get_free_memory_slack(libxl__gc *gc, uint32_t *free_mem_slack)
-{
-    int rc;
-    char *free_mem_slack_path = "/local/domain/0/memory/freemem-slack";
-    char *free_mem_slack_s, *endptr;
-    uint32_t target_memkb, max_memkb;
-
-retry:
-    free_mem_slack_s = libxl__xs_read(gc, XBT_NULL, free_mem_slack_path);
-    if (!free_mem_slack_s) {
-        rc = libxl__fill_dom0_memory_info(gc, &target_memkb, &max_memkb);
-        if (rc < 0)
-            return rc;
-        goto retry;
-    } else {
-        *free_mem_slack = strtoul(free_mem_slack_s, &endptr, 10);
-        if (*endptr != '\0') {
-            LIBXL__LOG_ERRNO(gc->owner, LIBXL__LOG_ERROR,
-                    "invalid free_mem_slack %s from %s\n",
-                    free_mem_slack_s, free_mem_slack_path);
-            return ERROR_FAIL;
-        }
-    }
-    return 0;
-}
-
 int libxl_set_memory_target(libxl_ctx *ctx, uint32_t domid,
         int32_t target_memkb, int relative, int enforce)
 {
@@ -4953,20 +4914,13 @@ int libxl_get_free_memory(libxl_ctx *ctx, uint32_t *memkb)
 {
     int rc = 0;
     libxl_physinfo info;
-    uint32_t freemem_slack;
     GC_INIT(ctx);
 
     rc = libxl_get_physinfo(ctx, &info);
-    if (rc < 0)
-        goto out;
-    rc = libxl__get_free_memory_slack(gc, &freemem_slack);
     if (rc < 0)
         goto out;
 
-    if ((info.free_pages + info.scrub_pages) * 4 > freemem_slack)
-        *memkb = (info.free_pages + info.scrub_pages) * 4 - freemem_slack;
-    else
-        *memkb = 0;
+    *memkb = (info.free_pages + info.scrub_pages) * 4;
 
 out:
     GC_FREE;
@@ -4978,18 +4932,13 @@ int libxl_wait_for_free_memory(libxl_ctx *ctx, uint32_t domid, uint32_t
 {
     int rc = 0;
     libxl_physinfo info;
-    uint32_t freemem_slack;
     GC_INIT(ctx);
 
-    rc = libxl__get_free_memory_slack(gc, &freemem_slack);
-    if (rc < 0)
-        goto out;
     while (wait_secs > 0) {
         rc = libxl_get_physinfo(ctx, &info);
         if (rc < 0)
             goto out;
-        if (info.free_pages * 4 >= freemem_slack &&
-            info.free_pages * 4 - freemem_slack >= memory_kb) {
+        if (info.free_pages * 4 >= memory_kb) {
             rc = 0;
             goto out;
         }