git.ipfire.org Git - thirdparty/openembedded/openembedded-core-contrib.git/blob

   1 Upstream-Status: Backport
   2 Signed-off-by: Ross Burton <ross.burton@arm.com>
   3
   4 PR28804: tune default stap -s ## buffer size on small RAM machines
   5
   6 Insert a forgotten division by num_online_cpu() to adjust downward the
   7 calculated bufsize.  Tweak normal defaults back to 128 * 2 * 64K
   8 (16MB) per CPU, as the stap man page indicates.  This may need further
   9 tweaking when balancing against staprun consumption performance, but
  10 at least we have the docs lined up with the code at the moment.
  11
  12 PR28804: tune default stap -s ## buffer size on small RAM machines
  13
  14 Use si_meminfo to limit default buffer size.  Note in the man page
  15 that the "-s ##" parameter is per-CPU.
  16
  17 diff --git a/man/stap.1.in b/man/stap.1.in
  18 index 55dbc2c93..285a27b34 100644
  19 --- a/man/stap.1.in
  20 +++ b/man/stap.1.in
  21 @@ -239,8 +239,8 @@ and average amount of time spent in each probe-point. Also shows
  22  the derivation for each probe-point.
  23  .TP
  24  .BI \-s " NUM"
  25 -Use NUM megabyte buffers for kernel-to-user data transfer.  On a
  26 -multiprocessor in bulk mode, this is a per-processor amount.
  27 +Use NUM megabyte buffers for kernel-to-user data transfer per processor.
  28 +The default is 16MB, or less on smaller memory machines.
  29  .TP
  30  .BI \-I " DIR"
  31  Add the given directory to the tapset search directory.  See the
  32 diff --git a/runtime/transport/transport.c b/runtime/transport/transport.c
  33 index 18ecccea2..44afff814 100644
  34 --- a/runtime/transport/transport.c
  35 +++ b/runtime/transport/transport.c
  36 @@ -72,8 +72,11 @@ static inline void _stp_unlock_inode(struct inode *inode);
  37  #include "procfs.c"
  38  #include "control.c"
  39
  40 -static unsigned _stp_nsubbufs = 256;
  41 -static unsigned _stp_subbuf_size = 8 * STP_BUFFER_SIZE; /* 64K */
  42 +/* set default buffer parameters.  User may override these via stap -s #, and
  43 +   the runtime may auto-shrink it on low memory machines too. */
  44 +/* NB: Note default in man/stap.1.in */
  45 +static unsigned _stp_nsubbufs = 128;
  46 +static unsigned _stp_subbuf_size = 2 * STP_BUFFER_SIZE; /* 2 * 64K */
  47
  48  /* module parameters */
  49  static int _stp_bufsize;
  50 @@ -602,17 +605,30 @@ static int _stp_transport_init(void)
  51          _stp_need_kallsyms_stext = 0;
  52  #endif
  53
  54 -       if (_stp_bufsize) {
  55 -               unsigned size = _stp_bufsize * 1024 * 1024;
  56 +        if (_stp_bufsize == 0) { // option not specified?
  57 +               struct sysinfo si;
  58 +                long _stp_bufsize_avail;
  59 +                si_meminfo(&si);
  60 +                _stp_bufsize_avail = (long)((si.freeram + si.bufferram) / 4 / num_online_cpus())
  61 +                        << PAGE_SHIFT; // limit to quarter of free ram total
  62 +                if ((_stp_nsubbufs * _stp_subbuf_size * num_online_cpus()) > _stp_bufsize_avail) {
  63 +                        _stp_bufsize = max_t (int, 1, _stp_bufsize_avail / 1024 / 1024);
  64 +                        dbug_trans(1, "Shrinking default _stp_bufsize to %d MB/cpu due to low free memory\n", _stp_bufsize);
  65 +                }
  66 +        }
  67 +
  68 +       if (_stp_bufsize) { // overridden by user or by si_meminfo heuristic?
  69 +               long size = _stp_bufsize * 1024 * 1024;
  70                 _stp_subbuf_size = 65536;
  71 +                // bump up subbuf size from 64K to 1M to keep _stp_nsubbufs not too large
  72                 while (size / _stp_subbuf_size > 64 &&
  73                        _stp_subbuf_size < 1024 * 1024) {
  74                         _stp_subbuf_size <<= 1;
  75                 }
  76                 _stp_nsubbufs = size / _stp_subbuf_size;
  77 -               dbug_trans(1, "Using %d subbufs of size %d\n", _stp_nsubbufs, _stp_subbuf_size);
  78         }
  79 -
  80 +        dbug_trans(1, "Using %d subbufs of size %d\n", _stp_nsubbufs, _stp_subbuf_size);
  81 +
  82         ret = _stp_transport_fs_init(THIS_MODULE->name);
  83         if (ret)
  84                 goto err0;