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Date: Thu, 5 Mar 2009 05:53:58 +0100 From: Frederic Weisbecker <fweisbec@...il.com> To: Ingo Molnar <mingo@...e.hu> Cc: Andrew Morton <akpm@...ux-foundation.org>, Lai Jiangshan <laijs@...fujitsu.com>, Linus Torvalds <torvalds@...ux-foundation.org>, Steven Rostedt <rostedt@...dmis.org>, Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org Subject: [PATCH 0/5 v2] Binary ftrace_printk This new iteration addresses Steven's reviews. Notably: - only build the ftrace_printk format section if CONFIG_TRACING is set - be scheduler tracing safe (don't use preempt_enable directly from ftrace_printk to avoid tracing recursion) - fix a loss of format string when a module is unloaded. Since we can loose it on the ring-buffer if it is in overwrite mode, we don't keep track of the format given by the modules to free them. We just copy their ftrace_printk string format forever. Note that it is safe against duplicate strings since we verify if the string is already present in our list before allocating a new one. --- An new optimization is making its way to ftrace. Its purpose is to make ftrace_printk() consuming less memory and become faster. Written by Lai Jiangshan, the approach is to delay the formatting job from tracing time to output time. Currently, a call to ftrace_printk will format the whole string and insert it into the ring buffer. Then you can read it on /debug/tracing/trace file. The new implementation stores the address of the format string and the binary parameters into the ring buffer, making the packet more compact and faster to insert. Later, when the user exports the traces, the format string is retrieved with the binary parameters and the formatting job is eventually done. Here is the result of a small comparative benchmark while putting the following ftrace_printk on the timer interrupt. ftrace_printk is the old implementation, ftrace_bprintk is a the new one: ftrace_printk("This is the timer interrupt: %llu", jiffies_64); After some time running on low load (no X, no really active processes): ftrace_printk: duration average: 2044 ns, avg of bytes stored per entry: 39 ftrace_bprintk: duration average: 1426 ns, avg of bytes stored per entry: 16 Higher load (started X and launched a cat running on a X console looping on traces printing): ftrace_printk: duration average: 8812 ns ftrace_bprintk: duration average: 2611 ns Which means the new implementation can be 70 % faster on higher load. And it consumes lesser memory on the ring buffer. The three first patches rebase against latest -tip the ftrace_bprintk work done by Lai few monthes ago. The two others integrate ftrace_bprintk as a replacement for the old ftrace_printk implementation and factorize the printf style format decoding which is now used by three functions. Frederic Weisbecker (2): tracing/core: drop the old ftrace_printk implementation in favour of ftrace_bprintk vsprintf: unify the format decoding layer for its 3 users Lai Jiangshan (3): add binary printf ftrace: infrastructure for supporting binary record ftrace: add ftrace_bprintk() include/asm-generic/vmlinux.lds.h | 3 + include/linux/ftrace.h | 44 ++- include/linux/module.h | 5 + include/linux/string.h | 7 + kernel/module.c | 6 + kernel/trace/Kconfig | 1 + kernel/trace/Makefile | 1 + kernel/trace/trace.c | 141 +++--- kernel/trace/trace.h | 8 +- kernel/trace/trace_functions_graph.c | 6 +- kernel/trace/trace_mmiotrace.c | 9 +- kernel/trace/trace_output.c | 31 +- kernel/trace/trace_output.h | 2 + kernel/trace/trace_printk.c | 138 +++++ lib/Kconfig | 3 + lib/vsprintf.c | 1006 ++++++++++++++++++++++++++-------- 16 files changed, 1087 insertions(+), 324 deletions(-) create mode 100644 kernel/trace/trace_printk.c -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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