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Commit d3d36e71 authored by Josh Gao's avatar Josh Gao
Browse files

atrace: don't use sendfile. 

sendfile appears to have horrendous performance when used with the
ftrace output file, being up to 100x slower than the naive read/write
loop.

Switch to doing that instead, speeding up atrace from:

    $ atrace --async_start sched freq; sleep 1; time atrace --async_stop > dummy
    c apturing trace...    0m08.93s real     0m00.08s user     0m07.98s system

to:

    $ atrace --async_start sched freq; sleep 1; time atrace --async_stop > dummy
    capturing trace...    0m00.78s real     0m00.07s user     0m00.21s system

Bug: http://b/37164190
Test: atrace --async_start sched freq; sleep 1; time atrace --async_stop > dummy
Change-Id: I22fe1871e263867f9ac54c8f5b474df824b4bc69
parent b7003ce5

cmds/atrace/atrace.cpp

+10 −6
Original line number Diff line number Diff line
@@ -26,7 +26,6 @@ 
#include <stdio.h>

#include <stdlib.h>

#include <string.h>

#include <sys/sendfile.h>

#include <time.h>

#include <unistd.h>

#include <zlib.h>
@@ -974,11 +973,16 @@ static void dumpTrace(int outFd) 
            fprintf(stderr, "error cleaning up zlib: %d\n", result);

        }

    } else {

        ssize_t sent = 0;

        while ((sent = sendfile(outFd, traceFD, NULL, 64*1024*1024)) > 0);

        if (sent == -1) {

            fprintf(stderr, "error dumping trace: %s (%d)\n", strerror(errno),

                    errno);

        char buf[4096];

        ssize_t rc;

        while ((rc = TEMP_FAILURE_RETRY(read(traceFD, buf, sizeof(buf)))) > 0) {

            if (!android::base::WriteFully(outFd, buf, rc)) {

                fprintf(stderr, "error writing trace: %s\n", strerror(errno));

                break;

            }

        }

        if (rc == -1) {

            fprintf(stderr, "error dumping trace: %s\n", strerror(errno));

        }

    }