Commit-ID: 6a279230391b63130070e0219b0ad09d34d28c89 Gitweb: http://git.kernel.org/tip/6a279230391b63130070e0219b0ad09d34d28c89 Author: Alexander Shishkin <[email protected]> AuthorDate: Wed, 14 Jan 2015 14:18:13 +0200 Committer: Ingo Molnar <[email protected]> CommitDate: Thu, 2 Apr 2015 17:14:10 +0200
perf: Add a capability for AUX_NO_SG pmus to do software double buffering For pmus that don't support scatter-gather for AUX data in hardware, it might still make sense to implement software double buffering to avoid losing data while the user is reading data out. For this purpose, add a pmu capability that guarantees multiple high-order chunks for AUX buffer, so that the pmu driver can do switchover tricks. To make use of this feature, add PERF_PMU_CAP_AUX_SW_DOUBLEBUF to your pmu's capability mask. This will make the ring buffer AUX allocation code ensure that the biggest high order allocation for the aux buffer pages is no bigger than half of the total requested buffer size, thus making sure that the buffer has at least two high order allocations. Signed-off-by: Alexander Shishkin <[email protected]> Signed-off-by: Peter Zijlstra (Intel) <[email protected]> Cc: Borislav Petkov <[email protected]> Cc: Frederic Weisbecker <[email protected]> Cc: H. Peter Anvin <[email protected]> Cc: Kaixu Xia <[email protected]> Cc: Linus Torvalds <[email protected]> Cc: Mike Galbraith <[email protected]> Cc: Paul Mackerras <[email protected]> Cc: Robert Richter <[email protected]> Cc: Stephane Eranian <[email protected]> Cc: Thomas Gleixner <[email protected]> Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Cc: [email protected] Link: http://lkml.kernel.org/r/1421237903-181015-5-git-send-email-alexander.shish...@linux.intel.com Signed-off-by: Ingo Molnar <[email protected]> --- include/linux/perf_event.h | 1 + kernel/events/ring_buffer.c | 15 ++++++++++++++- 2 files changed, 15 insertions(+), 1 deletion(-) diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h index d5a4a8e..13a1eb3 100644 --- a/include/linux/perf_event.h +++ b/include/linux/perf_event.h @@ -175,6 +175,7 @@ struct perf_event; #define PERF_PMU_CAP_NO_INTERRUPT 0x01 #define PERF_PMU_CAP_NO_NMI 0x02 #define PERF_PMU_CAP_AUX_NO_SG 0x04 +#define PERF_PMU_CAP_AUX_SW_DOUBLEBUF 0x08 /** * struct pmu - generic performance monitoring unit diff --git a/kernel/events/ring_buffer.c b/kernel/events/ring_buffer.c index ed0859e..6e3be7a 100644 --- a/kernel/events/ring_buffer.c +++ b/kernel/events/ring_buffer.c @@ -287,13 +287,26 @@ int rb_alloc_aux(struct ring_buffer *rb, struct perf_event *event, if (!has_aux(event)) return -ENOTSUPP; - if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) + if (event->pmu->capabilities & PERF_PMU_CAP_AUX_NO_SG) { /* * We need to start with the max_order that fits in nr_pages, * not the other way around, hence ilog2() and not get_order. */ max_order = ilog2(nr_pages); + /* + * PMU requests more than one contiguous chunks of memory + * for SW double buffering + */ + if ((event->pmu->capabilities & PERF_PMU_CAP_AUX_SW_DOUBLEBUF) && + !overwrite) { + if (!max_order) + return -EINVAL; + + max_order--; + } + } + rb->aux_pages = kzalloc_node(nr_pages * sizeof(void *), GFP_KERNEL, node); if (!rb->aux_pages) return -ENOMEM; -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to [email protected] More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
