From: Trond Myklebust <trondmy@gmail.com>
To: linux-nfs@vger.kernel.org
Subject: [PATCH] SUNRPC: Optimise transport balancing code
Date: Thu, 18 Jul 2019 08:08:04 -0400 [thread overview]
Message-ID: <20190718120804.108146-3-trond.myklebust@hammerspace.com> (raw)
In-Reply-To: <20190718120804.108146-2-trond.myklebust@hammerspace.com>
Moves the balancing code to avoid doing cursor changes on every search
iteration.
Signed-off-by: Trond Myklebust <trond.myklebust@hammerspace.com>
---
net/sunrpc/xprtmultipath.c | 67 +++++++++++++++++++++-----------------
1 file changed, 38 insertions(+), 29 deletions(-)
diff --git a/net/sunrpc/xprtmultipath.c b/net/sunrpc/xprtmultipath.c
index f3ecd0bee484..78c075a68c04 100644
--- a/net/sunrpc/xprtmultipath.c
+++ b/net/sunrpc/xprtmultipath.c
@@ -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);
}
/*
--
2.21.0
prev parent reply other threads:[~2019-07-18 12:11 UTC|newest]
Thread overview: 3+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-07-18 12:08 [PATCH] SUNRPC: Ensure the bvecs are reset when we re-encode the RPC request Trond Myklebust
2019-07-18 12:08 ` [PATCH] SUNRPC: Fix initialisation of struct rpc_xprt_switch Trond Myklebust
2019-07-18 12:08 ` Trond Myklebust [this message]
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