From: Steven Rostedt When the pages are removed from the ring buffer for things like splice they are freed with ring_buffer_free_read_page(). They are also allocated with ring_buffer_alloc_read_page(). Currently the ring buffer does not take advantage of this situation. Every time the page is freed, the ring buffer simply frees it. When a new page is needed, it allocates it. This means that reading several pages with splice will cause a page to be freed and allocated several times. This is simply a waste. This patch adds a cache of the pages freed (16 max). This allows the pages to be reused quickly without need to go back to the memory pool. v2: Added in locking that should have been there in the first release. Reported-by: Mathieu Desnoyers Signed-off-by: Steven Rostedt --- kernel/trace/ring_buffer.c | 52 ++++++++++++++++++++++++++++++++++++++------ 1 files changed, 45 insertions(+), 7 deletions(-) diff --git a/kernel/trace/ring_buffer.c b/kernel/trace/ring_buffer.c index 7f6059c..7aded7d 100644 --- a/kernel/trace/ring_buffer.c +++ b/kernel/trace/ring_buffer.c @@ -157,6 +157,8 @@ static unsigned long ring_buffer_flags __read_mostly = RB_BUFFERS_ON; #define BUF_PAGE_HDR_SIZE offsetof(struct buffer_data_page, data) +#define RB_MAX_FREE_PAGES 16 + /** * tracing_on - enable all tracing buffers * @@ -325,7 +327,10 @@ EXPORT_SYMBOL_GPL(ring_buffer_event_data); #define RB_MISSED_STORED (1 << 30) struct buffer_data_page { - u64 time_stamp; /* page time stamp */ + union { + struct buffer_data_page *next; /* for free pages */ + u64 time_stamp; /* page time stamp */ + }; local_t commit; /* write committed index */ unsigned char data[]; /* data of buffer page */ }; @@ -472,6 +477,10 @@ struct ring_buffer { atomic_t record_disabled; cpumask_var_t cpumask; + struct buffer_data_page *free_pages; + int nr_free_pages; + spinlock_t free_pages_lock; + struct lock_class_key *reader_lock_key; struct mutex mutex; @@ -1118,6 +1127,7 @@ struct ring_buffer *__ring_buffer_alloc(unsigned long size, unsigned flags, buffer->flags = flags; buffer->clock = trace_clock_local; buffer->reader_lock_key = key; + spin_lock_init(&buffer->free_pages_lock); /* need at least two pages */ if (buffer->pages < 2) @@ -1184,6 +1194,7 @@ EXPORT_SYMBOL_GPL(__ring_buffer_alloc); void ring_buffer_free(struct ring_buffer *buffer) { + struct buffer_data_page *bpage; int cpu; get_online_cpus(); @@ -1200,6 +1211,11 @@ ring_buffer_free(struct ring_buffer *buffer) kfree(buffer->buffers); free_cpumask_var(buffer->cpumask); + while (buffer->free_pages) { + bpage = buffer->free_pages; + buffer->free_pages = bpage->next; + free_page((unsigned long)bpage); + }; kfree(buffer); } EXPORT_SYMBOL_GPL(ring_buffer_free); @@ -3714,14 +3730,24 @@ EXPORT_SYMBOL_GPL(ring_buffer_swap_cpu); */ void *ring_buffer_alloc_read_page(struct ring_buffer *buffer) { - struct buffer_data_page *bpage; + struct buffer_data_page *bpage = NULL; unsigned long addr; - addr = __get_free_page(GFP_KERNEL); - if (!addr) - return NULL; + spin_lock(&buffer->free_pages_lock); + if (buffer->free_pages) { + bpage = buffer->free_pages; + buffer->free_pages = bpage->next; + buffer->nr_free_pages--; + } + spin_unlock(&buffer->free_pages_lock); - bpage = (void *)addr; + if (!bpage) { + addr = __get_free_page(GFP_KERNEL); + if (!addr) + return NULL; + + bpage = (void *)addr; + } rb_init_page(bpage); @@ -3738,7 +3764,19 @@ EXPORT_SYMBOL_GPL(ring_buffer_alloc_read_page); */ void ring_buffer_free_read_page(struct ring_buffer *buffer, void *data) { - free_page((unsigned long)data); + struct buffer_data_page *bpage = data; + + spin_lock(&buffer->free_pages_lock); + if (buffer->nr_free_pages >= RB_MAX_FREE_PAGES) { + spin_unlock(&buffer->free_pages_lock); + free_page((unsigned long)data); + return; + } + + bpage->next = buffer->free_pages; + buffer->free_pages = bpage; + buffer->nr_free_pages++; + spin_unlock(&buffer->free_pages_lock); } EXPORT_SYMBOL_GPL(ring_buffer_free_read_page); -- 1.7.0 -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/