Commit f554af28 authored by Trond Myklebust's avatar Trond Myklebust
Browse files

SUNRPC: Optimise transport balancing code 



Moves the balancing code to avoid doing cursor changes on every search
iteration.

Signed-off-by: default avatarTrond Myklebust <trond.myklebust@hammerspace.com>
parent 75369089

net/sunrpc/xprtmultipath.c

+38 −29
Original line number Diff line number Diff line
@@ -19,7 +19,7 @@ 
#include <linux/sunrpc/addr.h>

#include <linux/sunrpc/xprtmultipath.h>



typedef struct rpc_xprt *(*xprt_switch_find_xprt_t)(struct list_head *head,

typedef struct rpc_xprt *(*xprt_switch_find_xprt_t)(struct rpc_xprt_switch *xps,

		const struct rpc_xprt *cur);



static const struct rpc_xprt_iter_ops rpc_xprt_iter_singular;
@@ -291,22 +291,15 @@ struct rpc_xprt *xprt_switch_find_next_entry(struct list_head *head, 
}



static

struct rpc_xprt *xprt_switch_set_next_cursor(struct list_head *head,

struct rpc_xprt *xprt_switch_set_next_cursor(struct rpc_xprt_switch *xps,

		struct rpc_xprt **cursor,

		xprt_switch_find_xprt_t find_next)

{

	struct rpc_xprt *cur, *pos, *old;

	struct rpc_xprt *pos, *old;



	cur = READ_ONCE(*cursor);

	for (;;) {

		old = cur;

		pos = find_next(head, old);

		if (pos == NULL)

			break;

		cur = cmpxchg_relaxed(cursor, old, pos);

		if (cur == old)

			break;

	}

	old = smp_load_acquire(cursor);

	pos = find_next(xps, old);

	smp_store_release(cursor, pos);

	return pos;

}
@@ -318,13 +311,11 @@ struct rpc_xprt *xprt_iter_next_entry_multiple(struct rpc_xprt_iter *xpi, 


	if (xps == NULL)

		return NULL;

	return xprt_switch_set_next_cursor(&xps->xps_xprt_list,

			&xpi->xpi_cursor,

			find_next);

	return xprt_switch_set_next_cursor(xps, &xpi->xpi_cursor, find_next);

}



static

struct rpc_xprt *xprt_switch_find_next_entry_roundrobin(struct list_head *head,

struct rpc_xprt *__xprt_switch_find_next_entry_roundrobin(struct list_head *head,

		const struct rpc_xprt *cur)

{

	struct rpc_xprt *ret;
@@ -336,31 +327,49 @@ struct rpc_xprt *xprt_switch_find_next_entry_roundrobin(struct list_head *head, 
}



static

struct rpc_xprt *xprt_iter_next_entry_roundrobin(struct rpc_xprt_iter *xpi)

struct rpc_xprt *xprt_switch_find_next_entry_roundrobin(struct rpc_xprt_switch *xps,

		const struct rpc_xprt *cur)

{

	struct rpc_xprt_switch *xps = rcu_dereference(xpi->xpi_xpswitch);

	struct list_head *head = &xps->xps_xprt_list;

	struct rpc_xprt *xprt;

	unsigned long xprt_queuelen;

	unsigned long xps_queuelen;

	unsigned int nactive;



	do {

		xprt = xprt_iter_next_entry_multiple(xpi,

			xprt_switch_find_next_entry_roundrobin);

		if (xprt == NULL)

	for (;;) {

		unsigned long xprt_queuelen, xps_queuelen;



		xprt = __xprt_switch_find_next_entry_roundrobin(head, cur);

		if (!xprt)

			break;

		xprt_queuelen = atomic_long_read(&xprt->queuelen);

		if (xprt_queuelen <= 2)

			break;

		xps_queuelen = atomic_long_read(&xps->xps_queuelen);

		nactive = READ_ONCE(xps->xps_nactive);

		/* Exit loop if xprt_queuelen <= average queue length */

	} while (xprt_queuelen * READ_ONCE(xps->xps_nactive) > xps_queuelen);

		if (xprt_queuelen * nactive <= xps_queuelen)

			break;

		cur = xprt;

	}

	return xprt;

}



static

struct rpc_xprt *xprt_iter_next_entry_roundrobin(struct rpc_xprt_iter *xpi)

{

	return xprt_iter_next_entry_multiple(xpi,

			xprt_switch_find_next_entry_roundrobin);

}



static

struct rpc_xprt *xprt_switch_find_next_entry_all(struct rpc_xprt_switch *xps,

		const struct rpc_xprt *cur)

{

	return xprt_switch_find_next_entry(&xps->xps_xprt_list, cur);

}



static

struct rpc_xprt *xprt_iter_next_entry_all(struct rpc_xprt_iter *xpi)

{

	return xprt_iter_next_entry_multiple(xpi, xprt_switch_find_next_entry);

	return xprt_iter_next_entry_multiple(xpi,

			xprt_switch_find_next_entry_all);

}



/*