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    Subject[PATCH 0/5 v3] Binary ftrace_printk
    Changelog V3:

    Rebase the whole against latest tip/master

    Changelog V2:

    This new iteration addresses Steven's reviews.

    - 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.

    Changelog V1:

    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

    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
    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/ | 9 +
    include/linux/ftrace.h | 1 -
    include/linux/kernel.h | 34 +-
    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 | 41 ++-
    kernel/trace/trace_output.h | 2 +
    kernel/trace/trace_printk.c | 138 +++++
    lib/Kconfig | 3 +
    lib/vsprintf.c | 1006 ++++++++++++++++++++++++++--------
    17 files changed, 1096 insertions(+), 322 deletions(-)
    create mode 100644 kernel/trace/trace_printk.c

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      Last update: 2009-03-06 17:33    [W:0.033 / U:14.456 seconds]
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