From 7b732a75047738e4f85438ed2f9cd34bf5f2a19a Mon Sep 17 00:00:00 2001 From: Peter Zijlstra Date: Mon, 23 Mar 2009 18:22:10 +0100 Subject: perf_counter: new output ABI - part 1 Impact: Rework the perfcounter output ABI use sys_read() only for instant data and provide mmap() output for all async overflow data. The first mmap() determines the size of the output buffer. The mmap() size must be a PAGE_SIZE multiple of 1+pages, where pages must be a power of 2 or 0. Further mmap()s of the same fd must have the same size. Once all maps are gone, you can again mmap() with a new size. In case of 0 extra pages there is no data output and the first page only contains meta data. When there are data pages, a poll() event will be generated for each full page of data. Furthermore, the output is circular. This means that although 1 page is a valid configuration, its useless, since we'll start overwriting it the instant we report a full page. Future work will focus on the output format (currently maintained) where we'll likey want each entry denoted by a header which includes a type and length. Further future work will allow to splice() the fd, also containing the async overflow data -- splice() would be mutually exclusive with mmap() of the data. Signed-off-by: Peter Zijlstra Cc: Paul Mackerras Orig-LKML-Reference: <20090323172417.470536358@chello.nl> Signed-off-by: Ingo Molnar --- include/linux/perf_counter.h | 36 +++++++++++++++--------------------- 1 file changed, 15 insertions(+), 21 deletions(-) (limited to 'include/linux/perf_counter.h') diff --git a/include/linux/perf_counter.h b/include/linux/perf_counter.h index 40b324e91bf6..2b5e66d5ebdf 100644 --- a/include/linux/perf_counter.h +++ b/include/linux/perf_counter.h @@ -152,6 +152,8 @@ struct perf_counter_mmap_page { __u32 lock; /* seqlock for synchronization */ __u32 index; /* hardware counter identifier */ __s64 offset; /* add to hardware counter value */ + + __u32 data_head; /* head in the data section */ }; #ifdef __KERNEL__ @@ -218,21 +220,6 @@ struct hw_perf_counter { #endif }; -/* - * Hardcoded buffer length limit for now, for IRQ-fed events: - */ -#define PERF_DATA_BUFLEN 2048 - -/** - * struct perf_data - performance counter IRQ data sampling ... - */ -struct perf_data { - int len; - int rd_idx; - int overrun; - u8 data[PERF_DATA_BUFLEN]; -}; - struct perf_counter; /** @@ -256,6 +243,14 @@ enum perf_counter_active_state { struct file; +struct perf_mmap_data { + struct rcu_head rcu_head; + int nr_pages; + atomic_t head; + struct perf_counter_mmap_page *user_page; + void *data_pages[0]; +}; + /** * struct perf_counter - performance counter kernel representation: */ @@ -289,16 +284,15 @@ struct perf_counter { int oncpu; int cpu; - /* pointer to page shared with userspace via mmap */ - unsigned long user_page; + /* mmap bits */ + struct mutex mmap_mutex; + atomic_t mmap_count; + struct perf_mmap_data *data; - /* read() / irq related data */ + /* poll related */ wait_queue_head_t waitq; /* optional: for NMIs */ int wakeup_pending; - struct perf_data *irqdata; - struct perf_data *usrdata; - struct perf_data data[2]; void (*destroy)(struct perf_counter *); struct rcu_head rcu_head; -- cgit v1.2.2