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    Subject[tip:perf/core] perf: Optimize perf_output_copy()
    Commit-ID:  5d967a8be636a4f301a8daad642bd1007299d9ec
    Gitweb: http://git.kernel.org/tip/5d967a8be636a4f301a8daad642bd1007299d9ec
    Author: Peter Zijlstra <a.p.zijlstra@chello.nl>
    AuthorDate: Thu, 20 May 2010 16:46:39 +0200
    Committer: Ingo Molnar <mingo@elte.hu>
    CommitDate: Fri, 21 May 2010 11:37:59 +0200

    perf: Optimize perf_output_copy()

    Reduce the clutter in perf_output_copy() by keeping
    an interator in perf_output_handle.

    Signed-off-by: Peter Zijlstra <a.p.zijlstra@chello.nl>
    Cc: Arnaldo Carvalho de Melo <acme@redhat.com>
    Cc: Frederic Weisbecker <fweisbec@gmail.com>
    Cc: Paul Mackerras <paulus@samba.org>
    Cc: Mike Galbraith <efault@gmx.de>
    Cc: Steven Rostedt <rostedt@goodmis.org>
    LKML-Reference: <20100521090710.742809176@chello.nl>
    Signed-off-by: Ingo Molnar <mingo@elte.hu>
    ---
    include/linux/perf_event.h | 3 ++
    kernel/perf_event.c | 54 +++++++++++++++++++++----------------------
    2 files changed, 29 insertions(+), 28 deletions(-)

    diff --git a/include/linux/perf_event.h b/include/linux/perf_event.h
    index 7098ebb..7bd17f0 100644
    --- a/include/linux/perf_event.h
    +++ b/include/linux/perf_event.h
    @@ -806,6 +806,9 @@ struct perf_output_handle {
    unsigned long head;
    unsigned long offset;
    unsigned long wakeup;
    + unsigned long size;
    + void *addr;
    + int page;
    int nmi;
    int sample;
    };
    diff --git a/kernel/perf_event.c b/kernel/perf_event.c
    index 1531e0b..b67549a 100644
    --- a/kernel/perf_event.c
    +++ b/kernel/perf_event.c
    @@ -2961,39 +2961,30 @@ again:
    void perf_output_copy(struct perf_output_handle *handle,
    const void *buf, unsigned int len)
    {
    - unsigned int pages_mask;
    - unsigned long offset;
    - unsigned int size;
    - void **pages;
    -
    - offset = handle->offset;
    - pages_mask = handle->data->nr_pages - 1;
    - pages = handle->data->data_pages;
    -
    - do {
    - unsigned long page_offset;
    - unsigned long page_size;
    - int nr;
    -
    - nr = (offset >> PAGE_SHIFT) & pages_mask;
    - page_size = 1UL << (handle->data->data_order + PAGE_SHIFT);
    - page_offset = offset & (page_size - 1);
    - size = min_t(unsigned int, page_size - page_offset, len);
    -
    - memcpy(pages[nr] + page_offset, buf, size);
    -
    - len -= size;
    - buf += size;
    - offset += size;
    - } while (len);
    -
    - handle->offset = offset;
    + handle->offset += len;

    /*
    * Check we didn't copy past our reservation window, taking the
    * possible unsigned int wrap into account.
    */
    - WARN_ON_ONCE(((long)(handle->head - handle->offset)) < 0);
    + if (WARN_ON_ONCE(((long)(handle->head - handle->offset)) < 0))
    + return;
    +
    + do {
    + unsigned long size = min(handle->size, len);
    +
    + memcpy(handle->addr, buf, size);
    +
    + len -= size;
    + handle->addr += size;
    + handle->size -= size;
    + if (!handle->size) {
    + handle->page++;
    + handle->page &= handle->data->nr_pages - 1;
    + handle->addr = handle->data->data_pages[handle->page];
    + handle->size = PAGE_SIZE << handle->data->data_order;
    + }
    + } while (len);
    }

    int perf_output_begin(struct perf_output_handle *handle,
    @@ -3059,6 +3050,13 @@ int perf_output_begin(struct perf_output_handle *handle,
    if (head - local_read(&data->wakeup) > data->watermark)
    local_add(data->watermark, &data->wakeup);

    + handle->page = handle->offset >> (PAGE_SHIFT + data->data_order);
    + handle->page &= data->nr_pages - 1;
    + handle->size = handle->offset & ((PAGE_SIZE << data->data_order) - 1);
    + handle->addr = data->data_pages[handle->page];
    + handle->addr += handle->size;
    + handle->size = (PAGE_SIZE << data->data_order) - handle->size;
    +
    if (have_lost) {
    lost_event.header.type = PERF_RECORD_LOST;
    lost_event.header.misc = 0;

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