include: posix.mman += MADV_* (MADV_NORMAL, MADV_DONTNEED, etc ...) #3012
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I was going to use posix_madvise(POSIX_MADV_DONTNEED) in my tests to make sure a memory page should be evicted from kernel cache, but found out that this operation is hardcoded to be NOOP on Glibc/Linux systems: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/posix_madvise.c;h=c89fa64f0749;hb=HEAD#l25 https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=8889e7aa461a On the other hand, as also verified by strace, `madvise(MADV_DONTNEED)` is not a NOOP as it actually goes to kernel by making syscall. Since it is not possible to use posix_madvise for what should be POSIX_MADV_DONTNEED behaviour, let's add all raw madvise behaviour flags as documented on http://man7.org/linux/man-pages/man2/madvise.2.html Presumably MADV_NORMAL and other behaviours that should translate 1-1 to POSIX ones were omitted in 59ac999 (Add pxd for mmap & friends from "sys/mman.h" covering POSIX/Linux/BSD) to make people use the standardised POSIX interface. However given that it turned out to be not possible to use posix_madvise for all standard behaviours, system-specific madvise behaviours have to be used.
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( CI failures: while most variants passed tests ok, if I read logs correctly, there are several failures due to some network or travis flakiness - the failures are not related to the patch ) |
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@scoder, CI failure here is untrue; please have a look. Thanks beforehand, |
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Thanks |
navytux
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…ythonGH-3012) I was going to use posix_madvise(POSIX_MADV_DONTNEED) in my tests to make sure a memory page should be evicted from kernel cache, but found out that this operation is hardcoded to be NOOP on Glibc/Linux systems: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/posix_madvise.c;h=c89fa64f0749;hb=HEAD#l25 https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=8889e7aa461a On the other hand, as also verified by strace, `madvise(MADV_DONTNEED)` is not a NOOP as it actually goes to kernel by making syscall. Since it is not possible to use posix_madvise for what should be POSIX_MADV_DONTNEED behaviour, let's add all raw madvise behaviour flags as documented on http://man7.org/linux/man-pages/man2/madvise.2.html Presumably MADV_NORMAL and other behaviours that should translate 1-1 to POSIX ones were omitted in 59ac999 (Add pxd for mmap & friends from "sys/mman.h" covering POSIX/Linux/BSD) to make people use the standardised POSIX interface. However given that it turned out to be not possible to use posix_madvise for all standard behaviours, system-specific madvise behaviours have to be used. (cherry picked from commit b394295)
scoder
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Jul 19, 2019
…H-3012) I was going to use posix_madvise(POSIX_MADV_DONTNEED) in my tests to make sure a memory page should be evicted from kernel cache, but found out that this operation is hardcoded to be NOOP on Glibc/Linux systems: https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/posix_madvise.c;h=c89fa64f0749;hb=HEAD#l25 https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=8889e7aa461a On the other hand, as also verified by strace, `madvise(MADV_DONTNEED)` is not a NOOP as it actually goes to kernel by making syscall. Since it is not possible to use posix_madvise for what should be POSIX_MADV_DONTNEED behaviour, let's add all raw madvise behaviour flags as documented on http://man7.org/linux/man-pages/man2/madvise.2.html Presumably MADV_NORMAL and other behaviours that should translate 1-1 to POSIX ones were omitted in 59ac999 (Add pxd for mmap & friends from "sys/mman.h" covering POSIX/Linux/BSD) to make people use the standardised POSIX interface. However given that it turned out to be not possible to use posix_madvise for all standard behaviours, system-specific madvise behaviours have to be used. (cherry picked from commit b394295)
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I was going to use posix_madvise(POSIX_MADV_DONTNEED) in my tests to
make sure a memory page should be evicted from kernel cache, but found
out that this operation is hardcoded to be NOOP on Glibc/Linux systems:
https://sourceware.org/git/?p=glibc.git;a=blob;f=sysdeps/unix/sysv/linux/posix_madvise.c;h=c89fa64f0749;hb=HEAD#l25
https://sourceware.org/git/?p=glibc.git;a=commitdiff;h=8889e7aa461a
On the other hand, as also verified by strace,
madvise(MADV_DONTNEED)is not a NOOP as it actually goes to kernel by making syscall.
Since it is not possible to use posix_madvise for what should be
POSIX_MADV_DONTNEED behaviour, let's add all raw madvise behaviour flags
as documented on http://man7.org/linux/man-pages/man2/madvise.2.html
Presumably MADV_NORMAL and other behaviours that should translate 1-1 to
POSIX ones were omitted in 59ac999 (Add pxd for mmap & friends
from "sys/mman.h" covering POSIX/Linux/BSD) to make people use the
standardised POSIX interface. However given that it turned out to be not
possible to use posix_madvise for all standard behaviours,
system-specific madvise behaviours have to be used.