glibc/sysdeps/x86/dl-tunables.list

# x86 specific tunables.
# Copyright (C) 2017-2020 Free Software Foundation, Inc.
# This file is part of the GNU C Library.

# The GNU C Library is free software; you can redistribute it and/or
# modify it under the terms of the GNU Lesser General Public
# License as published by the Free Software Foundation; either
# version 2.1 of the License, or (at your option) any later version.

# The GNU C Library is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
# Lesser General Public License for more details.

# You should have received a copy of the GNU Lesser General Public
# License along with the GNU C Library; if not, see
# <https://www.gnu.org/licenses/>.

glibc {
  cpu {
    hwcaps {
      type: STRING
    }
    x86_ibt {
      type: STRING
    }
    x86_shstk {
      type: STRING
    }
    x86_non_temporal_threshold {
      type: SIZE_T
    }
    x86_rep_movsb_threshold {
      type: SIZE_T
      # Since there is overhead to set up REP MOVSB operation, REP MOVSB
      # isn't faster on short data.  The memcpy micro benchmark in glibc
      # shows that 2KB is the approximate value above which REP MOVSB
      # becomes faster than SSE2 optimization on processors with Enhanced
      # REP MOVSB.  Since larger register size can move more data with a
      # single load and store, the threshold is higher with larger register
      # size.  Note: Since the REP MOVSB threshold must be greater than 8
      # times of vector size and the default value is 2048 * (vector size
      # / 16), the default value and the minimum value must be updated at
      # run-time.  NB: Don't set the default value since we can't tell if
      # the tunable value is set by user or not [BZ #27069].
      minval: 1
    }
    x86_rep_stosb_threshold {
      type: SIZE_T
      # Since there is overhead to set up REP STOSB operation, REP STOSB
      # isn't faster on short data.  The memset micro benchmark in glibc
      # shows that 2KB is the approximate value above which REP STOSB
      # becomes faster on processors with Enhanced REP STOSB.  Since the
      # stored value is fixed, larger register size has minimal impact
      # on threshold.
      minval: 1
      default: 2048
    }
    x86_data_cache_size {
      type: SIZE_T
    }
    x86_shared_cache_size {
      type: SIZE_T
    }
  }
}