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Date: Wed, 25 Mar 2009 12:06:27 GMT
From: Peter Zijlstra <a.p.zijlstra@...llo.nl>
To: linux-tip-commits@...r.kernel.org
Cc: linux-kernel@...r.kernel.org, paulus@...ba.org, hpa@...or.com,
mingo@...hat.com, a.p.zijlstra@...llo.nl, efault@....de,
arjan@...radead.org, tglx@...utronix.de, fengguang.wu@...el.com,
mingo@...e.hu
Subject: [tip:perfcounters/core] perf_counter: more elaborate write API
Commit-ID: c3f81c52021ae1c90c2718aba5114fbd54db20ff
Gitweb: http://git.kernel.org/tip/c3f81c52021ae1c90c2718aba5114fbd54db20ff
Author: Peter Zijlstra <a.p.zijlstra@...llo.nl>
AuthorDate: Wed, 25 Mar 2009 12:30:22 +0100
Committer: Ingo Molnar <mingo@...e.hu>
CommitDate: Wed, 25 Mar 2009 13:02:51 +0100
perf_counter: more elaborate write API
Provide a begin, copy, end interface to the output buffer.
begin() reserves the space,
copy() copies the data over, considering page boundaries,
end() finalizes the event and does the wakeup.
Signed-off-by: Peter Zijlstra <a.p.zijlstra@...llo.nl>
Cc: Paul Mackerras <paulus@...ba.org>
Cc: Mike Galbraith <efault@....de>
Cc: Arjan van de Ven <arjan@...radead.org>
Cc: Wu Fengguang <fengguang.wu@...el.com>
LKML-Reference: <20090325113316.740550870@...llo.nl>
Signed-off-by: Ingo Molnar <mingo@...e.hu>
---
kernel/perf_counter.c | 109 +++++++++++++++++++++++++++++++++---------------
1 files changed, 75 insertions(+), 34 deletions(-)
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index affe227..0422fd9 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -9,6 +9,7 @@
*/
#include <linux/fs.h>
+#include <linux/mm.h>
#include <linux/cpu.h>
#include <linux/smp.h>
#include <linux/file.h>
@@ -16,15 +17,14 @@
#include <linux/sysfs.h>
#include <linux/ptrace.h>
#include <linux/percpu.h>
+#include <linux/vmstat.h>
+#include <linux/hardirq.h>
+#include <linux/rculist.h>
#include <linux/uaccess.h>
#include <linux/syscalls.h>
#include <linux/anon_inodes.h>
#include <linux/kernel_stat.h>
#include <linux/perf_counter.h>
-#include <linux/mm.h>
-#include <linux/vmstat.h>
-#include <linux/rculist.h>
-#include <linux/hardirq.h>
#include <asm/irq_regs.h>
@@ -1411,16 +1411,20 @@ static const struct file_operations perf_fops = {
* Output
*/
-static int perf_output_write(struct perf_counter *counter, int nmi,
- void *buf, ssize_t size)
+struct perf_output_handle {
+ struct perf_counter *counter;
+ struct perf_mmap_data *data;
+ unsigned int offset;
+ int wakeup;
+};
+
+static int perf_output_begin(struct perf_output_handle *handle,
+ struct perf_counter *counter, unsigned int size)
{
struct perf_mmap_data *data;
- unsigned int offset, head, nr;
- unsigned int len;
- int ret, wakeup;
+ unsigned int offset, head;
rcu_read_lock();
- ret = -ENOSPC;
data = rcu_dereference(counter->data);
if (!data)
goto out;
@@ -1428,45 +1432,82 @@ static int perf_output_write(struct perf_counter *counter, int nmi,
if (!data->nr_pages)
goto out;
- ret = -EINVAL;
- if (size > PAGE_SIZE)
- goto out;
-
do {
offset = head = atomic_read(&data->head);
head += size;
} while (atomic_cmpxchg(&data->head, offset, head) != offset);
- wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT);
+ handle->counter = counter;
+ handle->data = data;
+ handle->offset = offset;
+ handle->wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT);
- nr = (offset >> PAGE_SHIFT) & (data->nr_pages - 1);
- offset &= PAGE_SIZE - 1;
+ return 0;
- len = min_t(unsigned int, PAGE_SIZE - offset, size);
- memcpy(data->data_pages[nr] + offset, buf, len);
- size -= len;
+out:
+ rcu_read_unlock();
- if (size) {
- nr = (nr + 1) & (data->nr_pages - 1);
- memcpy(data->data_pages[nr], buf + len, size);
- }
+ return -ENOSPC;
+}
- /*
- * generate a poll() wakeup for every page boundary crossed
- */
- if (wakeup) {
- atomic_xchg(&data->wakeup, POLL_IN);
- __perf_counter_update_userpage(counter, data);
+static void perf_output_copy(struct perf_output_handle *handle,
+ void *buf, unsigned int len)
+{
+ unsigned int pages_mask;
+ unsigned int offset;
+ unsigned int size;
+ void **pages;
+
+ offset = handle->offset;
+ pages_mask = handle->data->nr_pages - 1;
+ pages = handle->data->data_pages;
+
+ do {
+ unsigned int page_offset;
+ int nr;
+
+ nr = (offset >> PAGE_SHIFT) & pages_mask;
+ page_offset = offset & (PAGE_SIZE - 1);
+ size = min_t(unsigned int, PAGE_SIZE - page_offset, len);
+
+ memcpy(pages[nr] + page_offset, buf, size);
+
+ len -= size;
+ buf += size;
+ offset += size;
+ } while (len);
+
+ handle->offset = offset;
+}
+
+static void perf_output_end(struct perf_output_handle *handle, int nmi)
+{
+ if (handle->wakeup) {
+ (void)atomic_xchg(&handle->data->wakeup, POLL_IN);
+ __perf_counter_update_userpage(handle->counter, handle->data);
if (nmi) {
- counter->wakeup_pending = 1;
+ handle->counter->wakeup_pending = 1;
set_perf_counter_pending();
} else
- wake_up(&counter->waitq);
+ wake_up(&handle->counter->waitq);
}
- ret = 0;
-out:
rcu_read_unlock();
+}
+
+static int perf_output_write(struct perf_counter *counter, int nmi,
+ void *buf, ssize_t size)
+{
+ struct perf_output_handle handle;
+ int ret;
+ ret = perf_output_begin(&handle, counter, size);
+ if (ret)
+ goto out;
+
+ perf_output_copy(&handle, buf, size);
+ perf_output_end(&handle, nmi);
+
+out:
return ret;
}
--
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