lkml.org 
[lkml]   [2009]   [Mar]   [4]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
Subject[RFC PATCH] perfcounters: provide expansion room in the ABI
Impact: ABI change

This expands several fields in the perf_counter_hw_event struct and adds
a "flags" argument to the perf_counter_open system call, in order that
features can be added in future without ABI changes.

In particular the record_type field is expanded to 64 bits, and the
space for flag bits has been expanded from 32 to 64 bits.

This also adds some new fields:

* read_format (64 bits) is intended to provide a way to specify what
userspace wants to get back when it does a read() on a simple
(non-interrupting) counter;

* exclude_idle (1 bit) provides a way for userspace to ask that events
that occur when the cpu is idle be excluded;

* extra_config_len will provide a way for userspace to supply an
arbitrary amount of extra machine-specific PMU configuration data
immediately following the perf_counter_hw_event struct, to allow
sophisticated users to program things such as instruction matching
CAMs and address range registers;

* __reserved_3 and __reserved_4 provide space for future expansion.

Signed-off-by: Paul Mackerras <paulus@samba.org>
---
This should provide plenty of room for future expansion, in fact maybe
it's a little over the top.
Ingo, if this looks OK, you can pull it from the rfc branch of my
perfcounters.git tree at:

git://git.kernel.org/pub/scm/linux/kernel/git/paulus/perfcounters.git rfc

include/linux/perf_counter.h | 12 +++++++++---
include/linux/syscalls.h | 2 +-
kernel/perf_counter.c | 10 +++++++---
3 files changed, 17 insertions(+), 7 deletions(-)
diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h
index 186efaf..c42455a 100644
--- a/include/linux/perf_counter.h
+++ b/include/linux/perf_counter.h
@@ -69,9 +69,10 @@ struct perf_counter_hw_event {
__s64 type;

__u64 irq_period;
- __u32 record_type;
+ __u64 record_type;
+ __u64 read_format;

- __u32 disabled : 1, /* off by default */
+ __u64 disabled : 1, /* off by default */
nmi : 1, /* NMI sampling */
raw : 1, /* raw event type */
inherit : 1, /* children inherit it */
@@ -80,10 +81,15 @@ struct perf_counter_hw_event {
exclude_user : 1, /* don't count user */
exclude_kernel : 1, /* ditto kernel */
exclude_hv : 1, /* ditto hypervisor */
+ exclude_idle : 1, /* don't count when idle */

- __reserved_1 : 23;
+ __reserved_1 : 55;
+
+ __u32 extra_config_len;
+ __u32 __reserved_4;

__u64 __reserved_2;
+ __u64 __reserved_3;
};

/*
diff --git a/include/linux/syscalls.h b/include/linux/syscalls.h
index 28ef2be..ab1d772 100644
--- a/include/linux/syscalls.h
+++ b/include/linux/syscalls.h
@@ -698,5 +698,5 @@ int kernel_execve(const char *filename, char *const argv[], char *const envp[]);

asmlinkage long sys_perf_counter_open(
const struct perf_counter_hw_event __user *hw_event_uptr,
- pid_t pid, int cpu, int group_fd);
+ pid_t pid, int cpu, int group_fd, unsigned long flags);
#endif
diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c
index 16b14ba..b2e8389 100644
--- a/kernel/perf_counter.c
+++ b/kernel/perf_counter.c
@@ -1683,16 +1683,16 @@ perf_counter_alloc(struct perf_counter_hw_event *hw_event,
}

/**
- * sys_perf_task_open - open a performance counter, associate it to a task/cpu
+ * sys_perf_counter_open - open a performance counter, associate it to a task/cpu
*
* @hw_event_uptr: event type attributes for monitoring/sampling
* @pid: target pid
* @cpu: target cpu
* @group_fd: group leader counter fd
*/
-SYSCALL_DEFINE4(perf_counter_open,
+SYSCALL_DEFINE5(perf_counter_open,
const struct perf_counter_hw_event __user *, hw_event_uptr,
- pid_t, pid, int, cpu, int, group_fd)
+ pid_t, pid, int, cpu, int, group_fd, unsigned long, flags)
{
struct perf_counter *counter, *group_leader;
struct perf_counter_hw_event hw_event;
@@ -1703,6 +1703,10 @@ SYSCALL_DEFINE4(perf_counter_open,
int fput_needed2 = 0;
int ret;

+ /* for future expandability... */
+ if (flags)
+ return -EINVAL;
+
if (copy_from_user(&hw_event, hw_event_uptr, sizeof(hw_event)) != 0)
return -EFAULT;

--
1.5.6.3


\
 
 \ /
  Last update: 2009-03-04 10:43    [from the cache]
©2003-2011 Jasper Spaans