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SUNRPC: Optimise transport balancing code 

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

Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
This commit is contained in:
Trond Myklebust 2019-07-16 13:27:23 -04:00
parent 7536908982
commit f554af280a
1 changed files with 38 additions and 29 deletions
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67
net/sunrpc/xprtmultipath.c
View File

@ -19,7 +19,7 @@
#include <linux/sunrpc/addr.h> #include <linux/sunrpc/addr.h>
#include <linux/sunrpc/xprtmultipath.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); const struct rpc_xprt *cur);
static const struct rpc_xprt_iter_ops rpc_xprt_iter_singular; 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 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, struct rpc_xprt **cursor,
xprt_switch_find_xprt_t find_next) xprt_switch_find_xprt_t find_next)
{ {
struct rpc_xprt *cur, *pos, *old; struct rpc_xprt *pos, *old;
cur = READ_ONCE(*cursor); old = smp_load_acquire(cursor);
for (;;) { pos = find_next(xps, old);
old = cur; smp_store_release(cursor, pos);
pos = find_next(head, old);
if (pos == NULL)
break;
cur = cmpxchg_relaxed(cursor, old, pos);
if (cur == old)
break;
}
return pos; return pos;
} }
@ -318,13 +311,11 @@ struct rpc_xprt *xprt_iter_next_entry_multiple(struct rpc_xprt_iter *xpi,
if (xps == NULL) if (xps == NULL)
return NULL; return NULL;
return xprt_switch_set_next_cursor(&xps->xps_xprt_list, return xprt_switch_set_next_cursor(xps, &xpi->xpi_cursor, find_next);
&xpi->xpi_cursor,
find_next);
} }
static 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) const struct rpc_xprt *cur)
{ {
struct rpc_xprt *ret; struct rpc_xprt *ret;
@ -336,31 +327,49 @@ struct rpc_xprt *xprt_switch_find_next_entry_roundrobin(struct list_head *head,
} }
static 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; struct rpc_xprt *xprt;
unsigned long xprt_queuelen; unsigned int nactive;
unsigned long xps_queuelen;
do { for (;;) {
xprt = xprt_iter_next_entry_multiple(xpi, unsigned long xprt_queuelen, xps_queuelen;
xprt_switch_find_next_entry_roundrobin);
if (xprt == NULL) xprt = __xprt_switch_find_next_entry_roundrobin(head, cur);
if (!xprt)
break; break;
xprt_queuelen = atomic_long_read(&xprt->queuelen); xprt_queuelen = atomic_long_read(&xprt->queuelen);
if (xprt_queuelen <= 2)
break;
xps_queuelen = atomic_long_read(&xps->xps_queuelen); xps_queuelen = atomic_long_read(&xps->xps_queuelen);
nactive = READ_ONCE(xps->xps_nactive);
/* Exit loop if xprt_queuelen <= average queue length */ /* 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; 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 static
struct rpc_xprt *xprt_iter_next_entry_all(struct rpc_xprt_iter *xpi) 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);
} }
/* /*