The patch titled
knfsd: make nfsd readahead params cache SMP-friendly
has been added to the -mm tree. Its filename is
knfsd-make-nfsd-readahead-params-cache-smp-friendly.patch
See http://www.zip.com.au/~akpm/linux/patches/stuff/added-to-mm.txt to find
out what to do about this
------------------------------------------------------
Subject: knfsd: make nfsd readahead params cache SMP-friendly
From: Greg Banks <gnb@xxxxxxxxxxxxxxxxx>
Make the nfsd read-ahead params cache more SMP-friendly by changing the single
global list and lock into a fixed 16-bucket hashtable with per-bucket locks.
This reduces spinlock contention in nfsd_read() on read-heavy workloads on
multiprocessor servers.
Testing was on a 4 CPU 4 NIC Altix using 4 IRIX clients each doing 1K
streaming reads at full line rate. The server had 128 nfsd threads, which
sizes the RA cache at 256 entries, of which only a handful were used. Flat
profiling shows nfsd_read(), including the inlined nfsd_get_raparms(), taking
10.4% of each CPU. This patch drops the contribution from nfsd() to 1.71% for
each CPU.
Signed-off-by: Greg Banks <gnb@xxxxxxxxxxxxxxxxx>
Signed-off-by: Neil Brown <neilb@xxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxx>
---
fs/nfsd/vfs.c | 60 +++++++++++++++++++++++++++++++++++-------------
1 files changed, 44 insertions(+), 16 deletions(-)
diff -puN fs/nfsd/vfs.c~knfsd-make-nfsd-readahead-params-cache-smp-friendly fs/nfsd/vfs.c
--- a/fs/nfsd/vfs.c~knfsd-make-nfsd-readahead-params-cache-smp-friendly
+++ a/fs/nfsd/vfs.c
@@ -54,6 +54,7 @@
#include <linux/nfsd_idmap.h>
#include <linux/security.h>
#endif /* CONFIG_NFSD_V4 */
+#include <linux/jhash.h>
#include <asm/uaccess.h>
@@ -81,10 +82,19 @@ struct raparms {
dev_t p_dev;
int p_set;
struct file_ra_state p_ra;
+ unsigned int p_hindex;
};
+struct raparm_hbucket {
+ struct raparms *pb_head;
+ spinlock_t pb_lock;
+} ____cacheline_aligned_in_smp;
+
static struct raparms * raparml;
-static struct raparms * raparm_cache;
+#define RAPARM_HASH_BITS 4
+#define RAPARM_HASH_SIZE (1<<RAPARM_HASH_BITS)
+#define RAPARM_HASH_MASK (RAPARM_HASH_SIZE-1)
+static struct raparm_hbucket raparm_hash[RAPARM_HASH_SIZE];
/*
* Called from nfsd_lookup and encode_dirent. Check if we have crossed
@@ -743,16 +753,20 @@ nfsd_sync_dir(struct dentry *dp)
* Obtain the readahead parameters for the file
* specified by (dev, ino).
*/
-static DEFINE_SPINLOCK(ra_lock);
static inline struct raparms *
nfsd_get_raparms(dev_t dev, ino_t ino)
{
struct raparms *ra, **rap, **frap = NULL;
int depth = 0;
+ unsigned int hash;
+ struct raparm_hbucket *rab;
+
+ hash = jhash_2words(dev, ino, 0xfeedbeef) & RAPARM_HASH_MASK;
+ rab = &raparm_hash[hash];
- spin_lock(&ra_lock);
- for (rap = &raparm_cache; (ra = *rap); rap = &ra->p_next) {
+ spin_lock(&rab->pb_lock);
+ for (rap = &rab->pb_head; (ra = *rap); rap = &ra->p_next) {
if (ra->p_ino == ino && ra->p_dev == dev)
goto found;
depth++;
@@ -761,7 +775,7 @@ nfsd_get_raparms(dev_t dev, ino_t ino)
}
depth = nfsdstats.ra_size*11/10;
if (!frap) {
- spin_unlock(&ra_lock);
+ spin_unlock(&rab->pb_lock);
return NULL;
}
rap = frap;
@@ -769,15 +783,16 @@ nfsd_get_raparms(dev_t dev, ino_t ino)
ra->p_dev = dev;
ra->p_ino = ino;
ra->p_set = 0;
+ ra->p_hindex = hash;
found:
- if (rap != &raparm_cache) {
+ if (rap != &rab->pb_head) {
*rap = ra->p_next;
- ra->p_next = raparm_cache;
- raparm_cache = ra;
+ ra->p_next = rab->pb_head;
+ rab->pb_head = ra;
}
ra->p_count++;
nfsdstats.ra_depth[depth*10/nfsdstats.ra_size]++;
- spin_unlock(&ra_lock);
+ spin_unlock(&rab->pb_lock);
return ra;
}
@@ -853,11 +868,12 @@ nfsd_vfs_read(struct svc_rqst *rqstp, st
/* Write back readahead params */
if (ra) {
- spin_lock(&ra_lock);
+ struct raparm_hbucket *rab = &raparm_hash[ra->p_hindex];
+ spin_lock(&rab->pb_lock);
ra->p_ra = file->f_ra;
ra->p_set = 1;
ra->p_count--;
- spin_unlock(&ra_lock);
+ spin_unlock(&rab->pb_lock);
}
if (err >= 0) {
@@ -1833,11 +1849,11 @@ nfsd_permission(struct svc_export *exp,
void
nfsd_racache_shutdown(void)
{
- if (!raparm_cache)
+ if (!raparml)
return;
dprintk("nfsd: freeing readahead buffers.\n");
kfree(raparml);
- raparm_cache = raparml = NULL;
+ raparml = NULL;
}
/*
* Initialize readahead param cache
@@ -1846,19 +1862,31 @@ int
nfsd_racache_init(int cache_size)
{
int i;
+ int j = 0;
+ int nperbucket;
- if (raparm_cache)
+
+ if (raparml)
return 0;
+ if (cache_size < 2*RAPARM_HASH_SIZE)
+ cache_size = 2*RAPARM_HASH_SIZE;
raparml = kmalloc(sizeof(struct raparms) * cache_size, GFP_KERNEL);
if (raparml != NULL) {
dprintk("nfsd: allocating %d readahead buffers.\n",
cache_size);
+ for (i = 0 ; i < RAPARM_HASH_SIZE ; i++) {
+ raparm_hash[i].pb_head = NULL;
+ spin_lock_init(&raparm_hash[i].pb_lock);
+ }
+ nperbucket = cache_size >> RAPARM_HASH_BITS;
memset(raparml, 0, sizeof(struct raparms) * cache_size);
for (i = 0; i < cache_size - 1; i++) {
- raparml[i].p_next = raparml + i + 1;
+ if (i % nperbucket == 0)
+ raparm_hash[j++].pb_head = raparml + i;
+ if (i % nperbucket < nperbucket-1)
+ raparml[i].p_next = raparml + i + 1;
}
- raparm_cache = raparml;
} else {
printk(KERN_WARNING
"nfsd: Could not allocate memory read-ahead cache.\n");
_
Patches currently in -mm which might be from gnb@xxxxxxxxxxxxxxxxx are
cpumask-add-highest_possible_node_id.patch
cpumask-export-cpu_online_map-and-cpu_possible_map.patch
cpumask-export-node_to_cpu_mask-consistently.patch
knfsd-knfsd-add-some-missing-newlines-in-printks.patch
knfsd-knfsd-remove-an-unused-variable-from-e_show.patch
knfsd-knfsd-remove-an-unused-variable-from-auth_unix_lookup.patch
knfsd-use-seq_start_token-instead-of-hardcoded-magic-void1.patch
knfsd-move-tempsock-aging-to-a-timer.patch
knfsd-move-tempsock-aging-to-a-timer-tidy.patch
knfsd-convert-sk_inuse-to-atomic_t.patch
knfsd-use-new-lock-for-svc_sock-deferred-list.patch
knfsd-convert-sk_reserved-to-atomic_t.patch
knfsd-test-and-set-sk_busy-atomically.patch
knfsd-split-svc_serv-into-pools.patch
knfsd-add-svc_get.patch
knfsd-add-svc_set_num_threads.patch
knfsd-use-svc_set_num_threads-to-manage-threads-in-knfsd.patch
knfsd-make-rpc-threads-pools-numa-aware.patch
knfsd-make-rpc-threads-pools-numa-aware-fix.patch
knfsd-allow-admin-to-set-nthreads-per-node.patch
knfsd-prepare-knfsd-for-support-of-rsize-wsize-of-up-to-1mb-over-tcp.patch
knfsd-make-nfsd-readahead-params-cache-smp-friendly.patch
knfsd-knfsd-cache-ipmap-per-tcp-socket.patch
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