[Xen-API] [PATCH 1 of 2] [CA-39743] Improvements to the wait_xen_free_mem function

[Jonathan Knowles <jonathan.knowles@xxxxxxxxxxxxx>]

# HG changeset patch
# User Jonathan Knowles <jonathan.knowles@xxxxxxxxxxxxx>
# Date 1270028088 -3600
# Node ID 73d8b966e6eb5a1f654f75e25387fd1afb184073
# Parent  652da54170ffe4b4d6f3e47bd1215f6811d9ab03
[CA-39743] Improvements to the wait_xen_free_mem function.

Improvements include:
* We read the values of free_memory and scrub_memory atomically (rather than 
separately).
* We exit early if (free_memory < required_memory) and (scrub_memory = 0) as 
it's unlikely that more will become free.
* We time out more quickly than before (64 seconds rather than 256 seconds).

Signed-off-by: Jonathan Knowles <jonathan.knowles@xxxxxxxxxxxxx>

diff -r 652da54170ff -r 73d8b966e6eb ocaml/xenops/memory.ml
--- a/ocaml/xenops/memory.ml    Wed Mar 31 10:34:47 2010 +0100
+++ b/ocaml/xenops/memory.ml    Wed Mar 31 10:34:48 2010 +0100
@@ -216,28 +216,31 @@
        then HVM.footprint_mib target_mib max_mib vcpus shadow_multiplier
        else Linux.footprint_mib target_mib
 
-let wait_xen_free_mem ~xc ?(maximum_wait_time_seconds=256) 
requested_memory_kib =
+let wait_xen_free_mem ~xc ?(maximum_wait_time_seconds=64) required_memory_kib =
        let rec wait accumulated_wait_time_seconds =
-               let free_memory_kib = get_free_memory_kib ~xc in
-               let scrub_memory_kib = get_scrub_memory_kib ~xc in
+               let host_info = Xc.physinfo xc in
+               let free_memory_kib =
+                       kib_of_pages (Int64.of_nativeint 
host_info.Xc.free_pages) in
+               let scrub_memory_kib =
+                       kib_of_pages (Int64.of_nativeint 
host_info.Xc.scrub_pages) in
                (* At exponentially increasing intervals, write  *)
                (* a debug message saying how long we've waited: *)
-               if is_power_of_2 accumulated_wait_time_seconds then
-                       debug
-                               "Waited %i second(s) for memory to become 
available: \
-                               %Ld free, %Ld scrub, %Ld requested"
-                               accumulated_wait_time_seconds free_memory_kib
-                               scrub_memory_kib requested_memory_kib;
-               if free_memory_kib >= requested_memory_kib
-               then true
-               else begin
-                       (* Give up if we've already waited the maximum amount 
of time. *)
-                       if accumulated_wait_time_seconds >= 
maximum_wait_time_seconds
-                       then false
-                       else begin
-                               Thread.delay 1.0;
-                               wait (accumulated_wait_time_seconds + 1)
-                       end
-               end
-       in
+               if is_power_of_2 accumulated_wait_time_seconds then debug
+                       "Waited %i second(s) for memory to become available: \
+                       %Ld KiB free, %Ld KiB scrub, %Ld KiB required"
+                       accumulated_wait_time_seconds
+                       free_memory_kib scrub_memory_kib required_memory_kib;
+               if free_memory_kib >= required_memory_kib
+                       (* We already have enough memory. *)
+                       then true else
+               if scrub_memory_kib = 0L
+                       (* We'll never have enough memory. *)
+                       then false else
+               if accumulated_wait_time_seconds >= maximum_wait_time_seconds
+                       (* We've waited long enough. *)
+                       then false else
+               begin
+                       Thread.delay 1.0;
+                       wait (accumulated_wait_time_seconds + 1)
+               end in
        wait 0
1 file changed, 24 insertions(+), 21 deletions(-)
ocaml/xenops/memory.ml |   45 ++++++++++++++++++++++++---------------------

Attachment: xen-api.hg-2.patch
Description: Text Data

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