The svc_procedure structure contains a number of very static fields
which describe each RPC call that can be made. However the pc_count
field is a counter of calls received. For any given workload there
will be some of these that are very hot cachelines indeed.
This patch moves the counters to a dynamically allocated per-cpu
area at the end of the svc_stat structure attached to the svc_serv.
The pc_count field is used only as an index into that area, so that the
svc_procedure cachelines remain constant after service initialisation.
The result is dramatically less time spent in svc_process() and
nfsd_dispatch() waiting for svc_procedure cachelines to bounce.
Tests on a 16 CPU Altix A4700 with 2 10gige Myricom cards, configured
separately (no bonding). Workload is 640 client threads doing directory
traverals with random small reads, from server RAM.
Before
======
Kernel profile:
% cumulative self self total
time samples samples calls 1/call 1/call name
6.33 2813.00 2813.00 29979 0.09 1.01 svc_process <----
^^^^
4.66 4883.00 2070.00 2065 1.00 1.00 spin_unlock_irqrestore
4.06 6687.00 1804.00 2182 0.83 1.00 nfsd_ofcache_lookup
3.20 8110.00 1423.00 10932 0.13 1.00 nfsd_dispatch <----
^^^^
3.03 9456.00 1346.00 1343 1.00 1.00 nfsd_cache_lookup
2.62 10622.00 1166.00 4645 0.25 1.01 svc_tcp_recvfrom
2.47 11720.00 1098.00 1096 1.00 1.00 ia64_spinlock_contention
Call rate:
nullarbor:~ # pmdumptext nfs3.server.calls
...
Thu Dec 13 01:45:27 194796.183
Thu Dec 13 01:45:28 194677.118
Thu Dec 13 01:45:29 193932.692
Thu Dec 13 01:45:30 194294.364
Thu Dec 13 01:45:31 194971.276
Thu Dec 13 01:45:32 194111.207
Thu Dec 13 01:45:33 194999.635
Thu Dec 13 01:45:34 195312.594
Thu Dec 13 01:45:35 195707.293
Thu Dec 13 01:45:36 194610.353
Thu Dec 13 01:45:37 195913.662
After
=====
Kernel profile:
% cumulative self self total
time samples samples calls 1/call 1/call name
5.32 2420.00 2420.00 2793 0.87 1.00 nfsd_ofcache_lookup
4.21 4337.00 1917.00 1894 1.01 1.01 spin_unlock_irqrestore
3.05 5723.00 1386.00 1375 1.01 1.01 ia64_spinlock_contention
2.76 6977.00 1254.00 1250 1.00 1.00 svc_export_put
2.67 8193.00 1216.00 1210 1.00 1.01 find_get_page
2.57 9362.00 1169.00 1247 0.94 1.01 svcauth_unix_set_client
...
0.93 29904.00 425.00 29154 0.01 1.02 svc_process <----
^^^^
...
0.35 38663.00 159.00 11859 0.01 1.01 nfsd_dispatch <----
^^^^
call rate:
nullarbor:~ # pmdumptext nfs3.server.calls
...
Thu Dec 13 06:35:43 242547.513
Thu Dec 13 06:35:44 242257.033
Thu Dec 13 06:35:45 242144.719
Thu Dec 13 06:35:46 242857.100
Thu Dec 13 06:35:47 241464.156
Thu Dec 13 06:35:48 241182.933
Thu Dec 13 06:35:49 241294.968
Thu Dec 13 06:35:50 241606.887
i.e. about a 24.2% improvement in call rate. Note, this includes the
performance gain from the previous patch which made svc_stat per-cpu.
Signed-off-by: Greg Banks <gnb@xxxxxxx>
Reviewed-by: David Chinner <dgc@xxxxxxx>
Reviewed-by: Peter Leckie <pleckie@xxxxxxxxxxxxxxxxx>
---
include/linux/sunrpc/stats.h | 1 +
include/linux/sunrpc/svc.h | 2 +-
net/sunrpc/stats.c | 2 +-
net/sunrpc/svc.c | 10 +++++++---
4 files changed, 10 insertions(+), 5 deletions(-)
Index: bfields/include/linux/sunrpc/stats.h
===================================================================
--- bfields.orig/include/linux/sunrpc/stats.h
+++ bfields/include/linux/sunrpc/stats.h
@@ -34,6 +34,7 @@ struct svc_stat {
rpcbadfmt,
rpcbadauth,
rpcbadclnt;
+ unsigned int callcnt[];
};
void rpc_proc_init(void);
Index: bfields/include/linux/sunrpc/svc.h
===================================================================
--- bfields.orig/include/linux/sunrpc/svc.h
+++ bfields/include/linux/sunrpc/svc.h
@@ -77,6 +77,7 @@ struct svc_pool {
struct svc_serv {
struct svc_program * sv_program; /* RPC program */
struct svc_stat * sv_stats_percpu;/* RPC statistics */
+ unsigned int sv_stats_ncalls;/* how many slots in svc_stat.callcnt[] */
spinlock_t sv_lock;
unsigned int sv_nrthreads; /* # of server threads */
unsigned int sv_maxconn; /* max connections allowed or
@@ -408,7 +409,7 @@ struct svc_procedure {
kxdrproc_t pc_release; /* XDR free result */
unsigned int pc_argsize; /* argument struct size */
unsigned int pc_ressize; /* result struct size */
- unsigned int pc_count; /* call count */
+ unsigned int pc_countidx; /* index into svc_stat.callcnt[] */
unsigned int pc_cachetype; /* cache info (NFS) */
unsigned int pc_xdrressize; /* maximum size of XDR reply */
};
Index: bfields/net/sunrpc/stats.c
===================================================================
--- bfields.orig/net/sunrpc/stats.c
+++ bfields/net/sunrpc/stats.c
@@ -91,12 +91,13 @@ static void svc_stat_accum(const struct
unsigned int *usp = (unsigned int *)sp;
int cpu;
int i;
+ int n = sizeof(*sp)/sizeof(unsigned int) + serv->sv_stats_ncalls;
memset(sp, 0, sizeof(*sp));
for_each_possible_cpu(cpu) {
unsigned int *ucsp = (unsigned int *)
per_cpu_ptr(serv->sv_stats_percpu, cpu);
- for (i = 0 ; i < sizeof(*sp)/sizeof(unsigned int) ; i++)
+ for (i = 0 ; i < n ; i++)
usp[i] += ucsp[i];
}
}
@@ -109,13 +110,17 @@ void svc_seq_show(struct seq_file *seq,
{
/* TODO: report call counts from the non-primary programs */
const struct svc_program *prog = serv->sv_program;
- struct svc_stat accum;
- struct svc_stat *statp = &accum;
+ struct svc_stat *statp;
const struct svc_procedure *proc;
const struct svc_version *vers;
unsigned int i, j;
- svc_stat_accum(serv, &accum);
+ statp = kzalloc(sizeof(struct svc_stat) +
+ sizeof(unsigned int) * serv->sv_stats_ncalls,
+ GFP_KERNEL);
+ if (!statp)
+ return;
+ svc_stat_accum(serv, statp);
seq_printf(seq,
"net %u %u %u %u\n",
@@ -136,9 +141,11 @@ void svc_seq_show(struct seq_file *seq,
continue;
seq_printf(seq, "proc%d %u", i, vers->vs_nproc);
for (j = 0; j < vers->vs_nproc; j++, proc++)
- seq_printf(seq, " %u", proc->pc_count);
+ seq_printf(seq, " %u", statp->callcnt[proc->pc_countidx]);
seq_putc(seq, '\n');
}
+
+ kfree(statp);
}
EXPORT_SYMBOL_GPL(svc_seq_show);
Index: bfields/net/sunrpc/svc.c
===================================================================
--- bfields.orig/net/sunrpc/svc.c
+++ bfields/net/sunrpc/svc.c
@@ -365,6 +365,7 @@ __svc_create(struct svc_program *prog, u
unsigned int vers;
unsigned int xdrsize;
unsigned int i;
+ unsigned int countidx = 0;
if (!(serv = kzalloc(sizeof(*serv), GFP_KERNEL)))
return NULL;
@@ -386,6 +387,8 @@ __svc_create(struct svc_program *prog, u
prog->pg_lovers = vers;
if (prog->pg_vers[vers]->vs_xdrsize > xdrsize)
xdrsize = prog->pg_vers[vers]->vs_xdrsize;
+ for (i = 0 ; i < prog->pg_vers[vers]->vs_nproc ; i++)
+ prog->pg_vers[vers]->vs_proc[i].pc_countidx = countidx++;
}
prog = prog->pg_next;
}
@@ -395,7 +398,9 @@ __svc_create(struct svc_program *prog, u
init_timer(&serv->sv_temptimer);
spin_lock_init(&serv->sv_lock);
- serv->sv_stats_percpu = __alloc_percpu(sizeof(struct svc_stat),
+ serv->sv_stats_ncalls = countidx;
+ serv->sv_stats_percpu = __alloc_percpu(sizeof(struct svc_stat) +
+ sizeof(unsigned int) * countidx,
__alignof__(struct svc_stat));
if (!serv->sv_stats_percpu) {
kfree(serv);
@@ -1098,8 +1103,8 @@ svc_process(struct svc_rqst *rqstp)
statp = resv->iov_base +resv->iov_len;
svc_putnl(resv, RPC_SUCCESS);
- /* Bump per-procedure stats counter */
- procp->pc_count++;
+ /* Bump per-procedure per-cpu stats counter */
+ SVC_INC_STAT(serv, callcnt[procp->pc_countidx]);
/* Initialize storage for argp and resp */
memset(rqstp->rq_argp, 0, procp->pc_argsize);
--
Greg
--
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