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3f4b61a0b8
Add x86_rep_movsb_threshold and x86_rep_stosb_threshold to tunables to update thresholds for "rep movsb" and "rep stosb" at run-time. Note that the user specified threshold for "rep movsb" smaller than the minimum threshold will be ignored. Reviewed-by: Carlos O'Donell <carlos@redhat.com>
65 lines
2.2 KiB
Plaintext
65 lines
2.2 KiB
Plaintext
# x86 specific tunables.
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# Copyright (C) 2017-2020 Free Software Foundation, Inc.
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# This file is part of the GNU C Library.
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# The GNU C Library is free software; you can redistribute it and/or
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# modify it under the terms of the GNU Lesser General Public
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# License as published by the Free Software Foundation; either
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# version 2.1 of the License, or (at your option) any later version.
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# The GNU C Library is distributed in the hope that it will be useful,
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# but WITHOUT ANY WARRANTY; without even the implied warranty of
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# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
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# Lesser General Public License for more details.
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# You should have received a copy of the GNU Lesser General Public
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# License along with the GNU C Library; if not, see
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# <https://www.gnu.org/licenses/>.
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glibc {
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cpu {
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hwcaps {
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type: STRING
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}
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x86_ibt {
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type: STRING
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}
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x86_shstk {
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type: STRING
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}
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x86_non_temporal_threshold {
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type: SIZE_T
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}
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x86_rep_movsb_threshold {
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type: SIZE_T
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# Since there is overhead to set up REP MOVSB operation, REP MOVSB
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# isn't faster on short data. The memcpy micro benchmark in glibc
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# shows that 2KB is the approximate value above which REP MOVSB
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# becomes faster than SSE2 optimization on processors with Enhanced
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# REP MOVSB. Since larger register size can move more data with a
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# single load and store, the threshold is higher with larger register
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# size. Note: Since the REP MOVSB threshold must be greater than 8
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# times of vector size, the minium value must be updated at run-time.
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minval: 1
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default: 2048
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}
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x86_rep_stosb_threshold {
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type: SIZE_T
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# Since there is overhead to set up REP STOSB operation, REP STOSB
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# isn't faster on short data. The memset micro benchmark in glibc
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# shows that 2KB is the approximate value above which REP STOSB
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# becomes faster on processors with Enhanced REP STOSB. Since the
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# stored value is fixed, larger register size has minimal impact
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# on threshold.
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minval: 1
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default: 2048
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}
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x86_data_cache_size {
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type: SIZE_T
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}
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x86_shared_cache_size {
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type: SIZE_T
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}
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}
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}
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