crush: apply chooseleaf_tries to firstn mode too

Parameterize the attempts for the _firstn choose method, and apply the
rule-specified tries count to firstn mode as well.  Note that we have
slightly different behavior here than with indep:

 If the firstn value is not specified for firstn, we pass through the
 normal attempt count.  This maintains compatibility with legacy behavior.
 Note that this is usually *not* actually N^2 work, though, because of the
 descend_once tunable.  However, descend_once is unfortunately *not* the
 same thing as 1 chooseleaf try because it is only checked on a reject but
 not on a collision.  Sigh.

 In contrast, for indep, if tries is not specified we default to 1
 recursive attempt, because that is simply more sane, and we have the
 option to do so.  The descend_once tunable has no effect for indep.

Reflects ceph.git commit 64aeded50d80942d66a5ec7b604ff2fcbf5d7b63.

Signed-off-by: Ilya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: Sage Weil <sage@inktank.com>

diff --git a/include/linux/crush/crush.h b/include/linux/crush/crush.h
index 2e50bab..07b8fd4 100644 (file)
--- a/include/linux/crush/crush.h
+++ b/include/linux/crush/crush.h
@@ -165,7 +165,10 @@ struct crush_map {
        __u32 choose_local_fallback_tries;
        /* choose attempts before giving up */ 
        __u32 choose_total_tries;
-       /* attempt chooseleaf inner descent once; on failure retry outer descent */
+       /* attempt chooseleaf inner descent once for firstn mode; on
+        * reject retry outer descent.  Note that this does *not*
+        * apply to a collision: in that case we will retry as we used
+        * to. */
        __u32 chooseleaf_descend_once;
 };
 

diff --git a/net/ceph/crush/mapper.c b/net/ceph/crush/mapper.c
index e3ade07..c343205 100644 (file)
--- a/net/ceph/crush/mapper.c
+++ b/net/ceph/crush/mapper.c
@@ -299,6 +299,8 @@ static int crush_choose_firstn(const struct crush_map *map,
                               const __u32 *weight, int weight_max,
                               int x, int numrep, int type,
                               int *out, int outpos,
+                              unsigned int attempts,
+                              unsigned int recurse_attempts,
                               int recurse_to_leaf,
                               int descend_once, int *out2)
 {
@@ -385,6 +387,7 @@ static int crush_choose_firstn(const struct crush_map *map,
                                                         weight, weight_max,
                                                         x, outpos+1, 0,
                                                         out2, outpos,
+                                                        recurse_attempts, 0,
                                                         0,
                                                         map->chooseleaf_descend_once,
                                                         NULL) <= outpos)
@@ -421,7 +424,7 @@ reject:
                                                 flocal <= in->size + map->choose_local_fallback_tries)
                                                /* exhaustive bucket search */
                                                retry_bucket = 1;
-                                       else if (ftotal <= map->choose_total_tries)
+                                       else if (ftotal <= attempts)
                                                /* then retry descent */
                                                retry_descent = 1;
                                        else
@@ -634,7 +637,8 @@ int crush_do_rule(const struct crush_map *map,
        __u32 step;
        int i, j;
        int numrep;
-       int choose_leaf_tries = 1;
+       int choose_tries = map->choose_total_tries;
+       int choose_leaf_tries = 0;
        const int descend_once = 0;
 
        if ((__u32)ruleno >= map->max_rules) {
@@ -701,6 +705,8 @@ int crush_do_rule(const struct crush_map *map,
                                                x, numrep,
                                                curstep->arg2,
                                                o+osize, j,
+                                               choose_tries,
+                                               choose_leaf_tries ? choose_leaf_tries : choose_tries,
                                                recurse_to_leaf,
                                                descend_once, c+osize);
                                } else {
@@ -711,8 +717,8 @@ int crush_do_rule(const struct crush_map *map,
                                                x, numrep, numrep,
                                                curstep->arg2,
                                                o+osize, j,
-                                               map->choose_total_tries,
-                                               choose_leaf_tries,
+                                               choose_tries,
+                                               choose_leaf_tries ? choose_leaf_tries : 1,
                                                recurse_to_leaf,
                                                c+osize,
                                                0);