vol: rate-limit volume usage updates

Add threshold and time rate-limit parameters for volume usage
updates to disk.  This reduces the amount of i/o needed for
volume usage statistics on very busy fileservers.  Set the
default to limit updates to one every 5 seconds per volume.

Reviewed-on: http://gerrit.openafs.org/5803
Reviewed-by: Derrick Brashear <shadow@dementix.org>
Reviewed-by: Tom Keiser <tkeiser@sinenomine.net>
Tested-by: BuildBot <buildbot@rampaginggeek.com>
(cherry picked from commit 639ca379e47fbe550d090fff9e635ad24e8e34f0)

Change-Id: I29b8240515afe5585b3eef000dbf40110fd4620f
Reviewed-on: http://gerrit.openafs.org/8582
Tested-by: BuildBot <buildbot@rampaginggeek.com>
Reviewed-by: Ken Dreyer <ktdreyer@ktdreyer.com>
Reviewed-by: Paul Smeddle <paul.smeddle@gmail.com>
Reviewed-by: Stephan Wiesand <stephan.wiesand@desy.de>

diff --git a/src/vol/volume.c b/src/vol/volume.c
index c8884db1365fa1d4986a7528f8831a51511a32a4..d5c45adee30c9972f15e8ced8e1e51bde5594119 100644 (file)
--- a/src/vol/volume.c
+++ b/src/vol/volume.c
@@ -512,6 +512,8 @@ VOptDefaults(ProgramType pt, VolumePackageOptions *opts)
     opts->canUseSALVSYNC = 0;
 
     opts->interrupt_rxcall = NULL;
+    opts->usage_threshold = 128;
+    opts->usage_rate_limit = 5;
 
 #ifdef FAST_RESTART
     opts->unsafe_attach = 1;
@@ -6533,10 +6535,16 @@ VBumpVolumeUsage_r(Volume * vp)
     if (now - V_dayUseDate(vp) > OneDay)
        VAdjustVolumeStatistics_r(vp);
     /*
-     * Save the volume header image to disk after every 128 bumps to dayUse.
+     * Save the volume header image to disk after a threshold of bumps to dayUse,
+     * at most every usage_rate_limit seconds.
      */
-    if ((V_dayUse(vp)++ & 127) == 0) {
+    V_dayUse(vp)++;
+    vp->usage_bumps_outstanding++;
+    if (vp->usage_bumps_outstanding >= vol_opts.usage_threshold
+       && vp->usage_bumps_next_write <= now) {
        Error error;
+       vp->usage_bumps_outstanding = 0;
+       vp->usage_bumps_next_write = now + vol_opts.usage_rate_limit;
        VUpdateVolume_r(&error, vp, VOL_UPDATE_WAIT);
     }
 }

diff --git a/src/vol/volume.h b/src/vol/volume.h
index c5517644314c004781fbbe2b94d5e5bc63dbbd9e..6468d6dae6085f374cdad6ad066a86de9b6f6725 100644 (file)
--- a/src/vol/volume.h
+++ b/src/vol/volume.h
@@ -255,6 +255,9 @@ typedef struct VolumePackageOptions {
     void (*interrupt_rxcall) (struct rx_call *call, afs_int32 error);
                                   /**< callback to interrupt RX calls accessing
                                    *   a going-offline volume */
+    afs_int32 usage_threshold;    /*< number of accesses before writing volume header */
+    afs_int32 usage_rate_limit;   /*< minimum number of seconds before writing volume
+                                   *  header, after usage_threshold is exceeded */
 } VolumePackageOptions;
 
 /* Magic numbers and version stamps for each type of file */
@@ -701,6 +704,8 @@ typedef struct Volume {
     VolumeVLRUState vlru;         /* state specific to the VLRU */
     FSSYNC_VolOp_info * pending_vol_op;  /* fssync command info for any pending vol ops */
 #endif /* AFS_DEMAND_ATTACH_FS */
+    int usage_bumps_outstanding; /**< to rate limit the usage update i/o by accesses */
+    int usage_bumps_next_write;  /**< to rate limit the usage update i/o by time */
 } Volume;
 
 struct volHeader {