The patch titled
Subject: relay: Use per CPU constructs for the relay channel buffer pointers
has been added to the -mm tree. Its filename is
relay-use-per-cpu-constructs-for-the-relay-channel-buffer-pointers.patch
This patch should soon appear at
http://ozlabs.org/~akpm/mmots/broken-out/relay-use-per-cpu-constructs-for-the-relay-channel-buffer-pointers.patch
and later at
http://ozlabs.org/~akpm/mmotm/broken-out/relay-use-per-cpu-constructs-for-the-relay-channel-buffer-pointers.patch
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*** Remember to use Documentation/SubmitChecklist when testing your code ***
The -mm tree is included into linux-next and is updated
there every 3-4 working days
------------------------------------------------------
From: Akash Goel <akash.goel@xxxxxxxxx>
Subject: relay: Use per CPU constructs for the relay channel buffer pointers
relay essentially needs to maintain the per CPU array of channel buffer
pointers but it manually creates that array. Instead its better to avail
the per CPU constructs, provided by the kernel, to allocate & access the
array of pointer to channel buffers.
Link: http://lkml.kernel.org/r/1470909140-25919-1-git-send-email-akash.goel@xxxxxxxxx
Signed-off-by: Akash Goel <akash.goel@xxxxxxxxx>
Reviewed-by: Chris Wilson <chris@xxxxxxxxxxxxxxxxxx>
Cc: Tvrtko Ursulin <tvrtko.ursulin@xxxxxxxxx>
Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx>
---
include/linux/relay.h | 17 +++++----
kernel/relay.c | 74 ++++++++++++++++++++++------------------
2 files changed, 52 insertions(+), 39 deletions(-)
diff -puN include/linux/relay.h~relay-use-per-cpu-constructs-for-the-relay-channel-buffer-pointers include/linux/relay.h
--- a/include/linux/relay.h~relay-use-per-cpu-constructs-for-the-relay-channel-buffer-pointers
+++ a/include/linux/relay.h
@@ -19,6 +19,7 @@
#include <linux/fs.h>
#include <linux/poll.h>
#include <linux/kref.h>
+#include <linux/percpu.h>
/*
* Tracks changes to rchan/rchan_buf structs
@@ -63,7 +64,7 @@ struct rchan
struct kref kref; /* channel refcount */
void *private_data; /* for user-defined data */
size_t last_toobig; /* tried to log event > subbuf size */
- struct rchan_buf *buf[NR_CPUS]; /* per-cpu channel buffers */
+ struct rchan_buf ** __percpu buf; /* per-cpu channel buffers */
int is_global; /* One global buffer ? */
struct list_head list; /* for channel list */
struct dentry *parent; /* parent dentry passed to open */
@@ -204,7 +205,7 @@ static inline void relay_write(struct rc
struct rchan_buf *buf;
local_irq_save(flags);
- buf = chan->buf[smp_processor_id()];
+ buf = *this_cpu_ptr(chan->buf);
if (unlikely(buf->offset + length > chan->subbuf_size))
length = relay_switch_subbuf(buf, length);
memcpy(buf->data + buf->offset, data, length);
@@ -230,12 +231,12 @@ static inline void __relay_write(struct
{
struct rchan_buf *buf;
- buf = chan->buf[get_cpu()];
+ buf = *get_cpu_ptr(chan->buf);
if (unlikely(buf->offset + length > buf->chan->subbuf_size))
length = relay_switch_subbuf(buf, length);
memcpy(buf->data + buf->offset, data, length);
buf->offset += length;
- put_cpu();
+ put_cpu_ptr(chan->buf);
}
/**
@@ -251,17 +252,19 @@ static inline void __relay_write(struct
*/
static inline void *relay_reserve(struct rchan *chan, size_t length)
{
- void *reserved;
- struct rchan_buf *buf = chan->buf[smp_processor_id()];
+ void *reserved = NULL;
+ struct rchan_buf *buf = *get_cpu_ptr(chan->buf);
if (unlikely(buf->offset + length > buf->chan->subbuf_size)) {
length = relay_switch_subbuf(buf, length);
if (!length)
- return NULL;
+ goto end;
}
reserved = buf->data + buf->offset;
buf->offset += length;
+end:
+ put_cpu_ptr(chan->buf);
return reserved;
}
diff -puN kernel/relay.c~relay-use-per-cpu-constructs-for-the-relay-channel-buffer-pointers kernel/relay.c
--- a/kernel/relay.c~relay-use-per-cpu-constructs-for-the-relay-channel-buffer-pointers
+++ a/kernel/relay.c
@@ -214,7 +214,7 @@ static void relay_destroy_buf(struct rch
__free_page(buf->page_array[i]);
relay_free_page_array(buf->page_array);
}
- chan->buf[buf->cpu] = NULL;
+ *per_cpu_ptr(chan->buf, buf->cpu) = NULL;
kfree(buf->padding);
kfree(buf);
kref_put(&chan->kref, relay_destroy_channel);
@@ -382,20 +382,21 @@ static void __relay_reset(struct rchan_b
*/
void relay_reset(struct rchan *chan)
{
+ struct rchan_buf *buf;
unsigned int i;
if (!chan)
return;
- if (chan->is_global && chan->buf[0]) {
- __relay_reset(chan->buf[0], 0);
+ if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
+ __relay_reset(buf, 0);
return;
}
mutex_lock(&relay_channels_mutex);
for_each_possible_cpu(i)
- if (chan->buf[i])
- __relay_reset(chan->buf[i], 0);
+ if ((buf = *per_cpu_ptr(chan->buf, i)))
+ __relay_reset(buf, 0);
mutex_unlock(&relay_channels_mutex);
}
EXPORT_SYMBOL_GPL(relay_reset);
@@ -440,7 +441,7 @@ static struct rchan_buf *relay_open_buf(
struct dentry *dentry;
if (chan->is_global)
- return chan->buf[0];
+ return *per_cpu_ptr(chan->buf, 0);
buf = relay_create_buf(chan);
if (!buf)
@@ -464,7 +465,7 @@ static struct rchan_buf *relay_open_buf(
__relay_reset(buf, 1);
if(chan->is_global) {
- chan->buf[0] = buf;
+ *per_cpu_ptr(chan->buf, 0) = buf;
buf->cpu = 0;
}
@@ -526,22 +527,24 @@ static int relay_hotcpu_callback(struct
{
unsigned int hotcpu = (unsigned long)hcpu;
struct rchan *chan;
+ struct rchan_buf *buf;
switch(action) {
case CPU_UP_PREPARE:
case CPU_UP_PREPARE_FROZEN:
mutex_lock(&relay_channels_mutex);
list_for_each_entry(chan, &relay_channels, list) {
- if (chan->buf[hotcpu])
+ if ((buf = *per_cpu_ptr(chan->buf, hotcpu)))
continue;
- chan->buf[hotcpu] = relay_open_buf(chan, hotcpu);
- if(!chan->buf[hotcpu]) {
+ buf = relay_open_buf(chan, hotcpu);
+ if(!buf) {
printk(KERN_ERR
"relay_hotcpu_callback: cpu %d buffer "
"creation failed\n", hotcpu);
mutex_unlock(&relay_channels_mutex);
return notifier_from_errno(-ENOMEM);
}
+ *per_cpu_ptr(chan->buf, hotcpu) = buf;
}
mutex_unlock(&relay_channels_mutex);
break;
@@ -583,6 +586,7 @@ struct rchan *relay_open(const char *bas
{
unsigned int i;
struct rchan *chan;
+ struct rchan_buf *buf;
if (!(subbuf_size && n_subbufs))
return NULL;
@@ -593,6 +597,7 @@ struct rchan *relay_open(const char *bas
if (!chan)
return NULL;
+ chan->buf = alloc_percpu(struct rchan_buf *);
chan->version = RELAYFS_CHANNEL_VERSION;
chan->n_subbufs = n_subbufs;
chan->subbuf_size = subbuf_size;
@@ -608,9 +613,10 @@ struct rchan *relay_open(const char *bas
mutex_lock(&relay_channels_mutex);
for_each_online_cpu(i) {
- chan->buf[i] = relay_open_buf(chan, i);
- if (!chan->buf[i])
+ buf = relay_open_buf(chan, i);
+ if (!buf)
goto free_bufs;
+ *per_cpu_ptr(chan->buf, i) = buf;
}
list_add(&chan->list, &relay_channels);
mutex_unlock(&relay_channels_mutex);
@@ -619,8 +625,8 @@ struct rchan *relay_open(const char *bas
free_bufs:
for_each_possible_cpu(i) {
- if (chan->buf[i])
- relay_close_buf(chan->buf[i]);
+ if ((buf = *per_cpu_ptr(chan->buf, i)))
+ relay_close_buf(buf);
}
kref_put(&chan->kref, relay_destroy_channel);
@@ -666,6 +672,7 @@ int relay_late_setup_files(struct rchan
unsigned int i, curr_cpu;
unsigned long flags;
struct dentry *dentry;
+ struct rchan_buf *buf;
struct rchan_percpu_buf_dispatcher disp;
if (!chan || !base_filename)
@@ -684,10 +691,11 @@ int relay_late_setup_files(struct rchan
if (chan->is_global) {
err = -EINVAL;
- if (!WARN_ON_ONCE(!chan->buf[0])) {
- dentry = relay_create_buf_file(chan, chan->buf[0], 0);
+ buf = *per_cpu_ptr(chan->buf, 0);
+ if (!WARN_ON_ONCE(!buf)) {
+ dentry = relay_create_buf_file(chan, buf, 0);
if (dentry && !WARN_ON_ONCE(!chan->is_global)) {
- relay_set_buf_dentry(chan->buf[0], dentry);
+ relay_set_buf_dentry(buf, dentry);
err = 0;
}
}
@@ -702,13 +710,14 @@ int relay_late_setup_files(struct rchan
* on all currently online CPUs.
*/
for_each_online_cpu(i) {
- if (unlikely(!chan->buf[i])) {
+ buf = *per_cpu_ptr(chan->buf, i);
+ if (unlikely(!buf)) {
WARN_ONCE(1, KERN_ERR "CPU has no buffer!\n");
err = -EINVAL;
break;
}
- dentry = relay_create_buf_file(chan, chan->buf[i], i);
+ dentry = relay_create_buf_file(chan, buf, i);
if (unlikely(!dentry)) {
err = -EINVAL;
break;
@@ -716,10 +725,10 @@ int relay_late_setup_files(struct rchan
if (curr_cpu == i) {
local_irq_save(flags);
- relay_set_buf_dentry(chan->buf[i], dentry);
+ relay_set_buf_dentry(buf, dentry);
local_irq_restore(flags);
} else {
- disp.buf = chan->buf[i];
+ disp.buf = buf;
disp.dentry = dentry;
smp_mb();
/* relay_channels_mutex must be held, so wait. */
@@ -822,11 +831,10 @@ void relay_subbufs_consumed(struct rchan
if (!chan)
return;
- if (cpu >= NR_CPUS || !chan->buf[cpu] ||
- subbufs_consumed > chan->n_subbufs)
+ buf = *per_cpu_ptr(chan->buf, cpu);
+ if (cpu >= NR_CPUS || !buf || subbufs_consumed > chan->n_subbufs)
return;
- buf = chan->buf[cpu];
if (subbufs_consumed > buf->subbufs_produced - buf->subbufs_consumed)
buf->subbufs_consumed = buf->subbufs_produced;
else
@@ -842,18 +850,19 @@ EXPORT_SYMBOL_GPL(relay_subbufs_consumed
*/
void relay_close(struct rchan *chan)
{
+ struct rchan_buf *buf;
unsigned int i;
if (!chan)
return;
mutex_lock(&relay_channels_mutex);
- if (chan->is_global && chan->buf[0])
- relay_close_buf(chan->buf[0]);
+ if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0)))
+ relay_close_buf(buf);
else
for_each_possible_cpu(i)
- if (chan->buf[i])
- relay_close_buf(chan->buf[i]);
+ if ((buf = *per_cpu_ptr(chan->buf, i)))
+ relay_close_buf(buf);
if (chan->last_toobig)
printk(KERN_WARNING "relay: one or more items not logged "
@@ -874,20 +883,21 @@ EXPORT_SYMBOL_GPL(relay_close);
*/
void relay_flush(struct rchan *chan)
{
+ struct rchan_buf *buf;
unsigned int i;
if (!chan)
return;
- if (chan->is_global && chan->buf[0]) {
- relay_switch_subbuf(chan->buf[0], 0);
+ if (chan->is_global && (buf = *per_cpu_ptr(chan->buf, 0))) {
+ relay_switch_subbuf(buf, 0);
return;
}
mutex_lock(&relay_channels_mutex);
for_each_possible_cpu(i)
- if (chan->buf[i])
- relay_switch_subbuf(chan->buf[i], 0);
+ if ((buf = *per_cpu_ptr(chan->buf, i)))
+ relay_switch_subbuf(buf, 0);
mutex_unlock(&relay_channels_mutex);
}
EXPORT_SYMBOL_GPL(relay_flush);
_
Patches currently in -mm which might be from akash.goel@xxxxxxxxx are
relay-use-per-cpu-constructs-for-the-relay-channel-buffer-pointers.patch
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