From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757238AbZEESe7 (ORCPT ); Tue, 5 May 2009 14:34:59 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754316AbZEESer (ORCPT ); Tue, 5 May 2009 14:34:47 -0400 Received: from hera.kernel.org ([140.211.167.34]:58290 "EHLO hera.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752676AbZEESeq (ORCPT ); Tue, 5 May 2009 14:34:46 -0400 Date: Tue, 5 May 2009 18:34:01 GMT From: tip-bot for Peter Zijlstra To: linux-tip-commits@vger.kernel.org Cc: linux-kernel@vger.kernel.org, paulus@samba.org, hpa@zytor.com, mingo@redhat.com, a.p.zijlstra@chello.nl, tglx@linutronix.de, cjashfor@linux.vnet.ibm.com, mingo@elte.hu Reply-To: mingo@redhat.com, hpa@zytor.com, paulus@samba.org, linux-kernel@vger.kernel.org, a.p.zijlstra@chello.nl, tglx@linutronix.de, cjashfor@linux.vnet.ibm.com, mingo@elte.hu In-Reply-To: <20090505155436.925084300@chello.nl> References: <20090505155436.925084300@chello.nl> Subject: [tip:perfcounters/core] perf_counter: uncouple data_head updates from wakeups Message-ID: Git-Commit-ID: c66de4a5be7913247bd83d79168f8e4420c9cfbc X-Mailer: tip-git-log-daemon MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8 Content-Disposition: inline X-Greylist: Sender IP whitelisted, not delayed by milter-greylist-4.0 (hera.kernel.org [127.0.0.1]); Tue, 05 May 2009 18:34:05 +0000 (UTC) Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Commit-ID: c66de4a5be7913247bd83d79168f8e4420c9cfbc Gitweb: http://git.kernel.org/tip/c66de4a5be7913247bd83d79168f8e4420c9cfbc Author: Peter Zijlstra AuthorDate: Tue, 5 May 2009 17:50:22 +0200 Committer: Ingo Molnar CommitDate: Tue, 5 May 2009 20:18:30 +0200 perf_counter: uncouple data_head updates from wakeups Keep data_head up-to-date irrespective of notifications. This fixes the case where you disable a counter and don't get a notification for the last few pending events, and it also allows polling usage. [ Impact: increase precision of perfcounter mmap-ed fields ] Suggested-by: Corey Ashford Signed-off-by: Peter Zijlstra Cc: Paul Mackerras LKML-Reference: <20090505155436.925084300@chello.nl> Signed-off-by: Ingo Molnar --- include/linux/perf_counter.h | 4 +++- kernel/perf_counter.c | 20 +++++++++----------- 2 files changed, 12 insertions(+), 12 deletions(-) diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index a356fa6..17b6310 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -362,9 +362,11 @@ struct perf_mmap_data { atomic_t head; /* write position */ atomic_t events; /* event limit */ - atomic_t wakeup_head; /* completed head */ + atomic_t done_head; /* completed head */ atomic_t lock; /* concurrent writes */ + atomic_t wakeup; /* needs a wakeup */ + struct perf_counter_mmap_page *user_page; void *data_pages[0]; }; diff --git a/kernel/perf_counter.c b/kernel/perf_counter.c index 5f86a11..ba5e921 100644 --- a/kernel/perf_counter.c +++ b/kernel/perf_counter.c @@ -1696,7 +1696,6 @@ struct perf_output_handle { struct perf_mmap_data *data; unsigned int offset; unsigned int head; - int wakeup; int nmi; int overflow; int locked; @@ -1752,8 +1751,7 @@ static void perf_output_unlock(struct perf_output_handle *handle) struct perf_mmap_data *data = handle->data; int head, cpu; - if (handle->wakeup) - data->wakeup_head = data->head; + data->done_head = data->head; if (!handle->locked) goto out; @@ -1764,13 +1762,11 @@ again: * before we publish the new head, matched by a rmb() in userspace when * reading this position. */ - while ((head = atomic_xchg(&data->wakeup_head, 0))) { + while ((head = atomic_xchg(&data->done_head, 0))) data->user_page->data_head = head; - handle->wakeup = 1; - } /* - * NMI can happen here, which means we can miss a wakeup_head update. + * NMI can happen here, which means we can miss a done_head update. */ cpu = atomic_xchg(&data->lock, 0); @@ -1779,7 +1775,7 @@ again: /* * Therefore we have to validate we did not indeed do so. */ - if (unlikely(atomic_read(&data->wakeup_head))) { + if (unlikely(atomic_read(&data->done_head))) { /* * Since we had it locked, we can lock it again. */ @@ -1789,7 +1785,7 @@ again: goto again; } - if (handle->wakeup) + if (atomic_xchg(&data->wakeup, 0)) perf_output_wakeup(handle); out: local_irq_restore(handle->flags); @@ -1824,7 +1820,9 @@ static int perf_output_begin(struct perf_output_handle *handle, handle->offset = offset; handle->head = head; - handle->wakeup = (offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT); + + if ((offset >> PAGE_SHIFT) != (head >> PAGE_SHIFT)) + atomic_set(&data->wakeup, 1); return 0; @@ -1882,7 +1880,7 @@ static void perf_output_end(struct perf_output_handle *handle) int events = atomic_inc_return(&data->events); if (events >= wakeup_events) { atomic_sub(wakeup_events, &data->events); - handle->wakeup = 1; + atomic_set(&data->wakeup, 1); } }