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Commit f18650ac authored by Ilya Dryomov's avatar Ilya Dryomov
Browse files

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: default avatarIlya Dryomov <ilya.dryomov@inktank.com>
Reviewed-by: default avatarSage Weil <sage@inktank.com>
parent be3226ac

include/linux/crush/crush.h

+4 −1
Original line number Diff line number Diff line
@@ -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;

};

net/ceph/crush/mapper.c

+10 −4
Original line number Diff line number Diff line
@@ -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 @@ static int crush_choose_firstn(const struct crush_map *map, 
						 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);