[PATCH man-pages v5] madvise.2: add documentation for MADV_COLLAPSE

[PATCH man-pages v5] madvise.2: add documentation for MADV_COLLAPSE

[Zach OKeefe]

From: Zach O'Keefe <zokeefe@google.com>

Linux 6.1 introduced MADV_COLLAPSE in upstream commit 7d8faaf15545
("mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse") and
upstream commit 34488399fa08 ("mm/madvise: add file and shmem support to
MADV_COLLAPSE").  Update the man-pages for madvise(2) and
process_madvise(2).

Link: https://lore.kernel.org/linux-mm/20220922224046.1143204-1-zokeefe@google.com/
Link: https://lore.kernel.org/linux-mm/20220706235936.2197195-1-zokeefe@google.com/
Signed-off-by: Zach O'Keefe <zokeefe@google.com>
---

v4[1] -> v5
- Rebased to latest master
- (Alejandro Colomar) Applied diff to remove spurious file and fix
  semantic newlines.
- (Alejandro Colomar) Reworded documentation describing behavior of
  setting errno when multiple hugepage-aligned/sized regions fail to
  collapse.

v3[2] -> v4
- Rebased to latest master
- (Alejandro Colomar) Fixed weird, non-ascii chars: e2 80 99 -> "'"
- (Alejandro Colomar) Replaced .BR with .B directive when the entire
  line was bold (no non-bold part)

[1] https://lore.kernel.org/linux-man/20221031225500.3994542-1-zokeefe@google.com/
[2] https://lore.kernel.org/linux-man/bb3b5c3c-3966-ea1a-6d84-4f7f3afa37ca@gmail.com/T/#u

 man2/madvise.2         | 91 +++++++++++++++++++++++++++++++++++++++++-
 man2/process_madvise.2 | 10 +++++
 2 files changed, 99 insertions(+), 2 deletions(-)

diff --git a/man2/madvise.2 b/man2/madvise.2
index edf805740..038e6023d 100644
--- a/man2/madvise.2
+++ b/man2/madvise.2
@@ -386,9 +386,10 @@ set (see
 .BR prctl (2)).
 .IP
 The
-.B MADV_HUGEPAGE
+.BR MADV_HUGEPAGE ,
+.BR MADV_NOHUGEPAGE ,
 and
-.B MADV_NOHUGEPAGE
+.B MADV_COLLAPSE
 operations are available only if the kernel was configured with
 .B CONFIG_TRANSPARENT_HUGEPAGE
 and file/shmem memory is only supported if the kernel was configured with
@@ -401,6 +402,82 @@ and
 .I length
 will not be backed by transparent hugepages.
 .TP
+.BR MADV_COLLAPSE " (since Linux 6.1)"
+.\" commit 7d8faaf155454f8798ec56404faca29a82689c77
+.\" commit 34488399fa08faaf664743fa54b271eb6f9e1321
+Perform a best-effort synchronous collapse of
+the native pages mapped by the memory range
+into Transparent Huge Pages (THPs).
+.B MADV_COLLAPSE
+operates on the current state of memory of the calling process and
+makes no persistent changes or guarantees on how pages will be mapped,
+constructed,
+or faulted in the future.
+.IP
+.B MADV_COLLAPSE
+supports private anonymous pages (see
+.BR mmap (2)),
+shmem pages,
+and file-backed pages.
+See
+.B MADV_HUGEPAGE
+for general information on memory requirements for THP.
+If the range provided spans multiple VMAs,
+the semantics of the collapse over each VMA is independent from the others.
+If collapse of a given huge page-aligned/sized region fails,
+the operation may continue to attempt collapsing
+the remainder of the specified memory.
+.B MADV_COLLAPSE
+will automatically clamp the provided range to be hugepage-aligned.
+.IP
+All non-resident pages covered by the range
+will first be swapped/faulted-in,
+before being copied onto a freshly allocated hugepage.
+If the native pages compose the same PTE-mapped hugepage,
+and are suitably aligned,
+allocation of a new hugepage may be elided and
+collapse may happen in-place.
+Unmapped pages will have their data directly initialized to 0
+in the new hugepage.
+However,
+for every eligible hugepage-aligned/sized region to be collapsed,
+at least one page must currently be backed by physical memory.
+.IP
+.B MADV_COLLAPSE
+is independent of any sysfs
+(see
+.BR sysfs (5))
+setting under
+.IR /sys/kernel/mm/transparent_hugepage ,
+both in terms of determining THP eligibility,
+and allocation semantics.
+See Linux kernel source file
+.I Documentation/admin\-guide/mm/transhuge.rst
+for more information.
+.B MADV_COLLAPSE
+also ignores
+.B huge=
+tmpfs mount when operating on tmpfs files.
+Allocation for the new hugepage may enter direct reclaim and/or compaction,
+regardless of VMA flags
+(though
+.B VM_NOHUGEPAGE
+is still respected).
+.IP
+When the system has multiple NUMA nodes,
+the hugepage will be allocated from
+the node providing the most native pages.
+.IP
+If all hugepage-sized/aligned regions covered by the provided range were
+either successfully collapsed,
+or were already PMD-mapped THPs,
+this operation will be deemed successful.
+Note that this doesn't guarantee anything about
+other possible mappings of the memory.
+In the event multiple hugepage-aligned/sized areas fail to collapse,
+only the most recently-failed code will be set in
+.IR errno .
+.TP
 .BR MADV_DONTDUMP " (since Linux 3.4)"
 .\" commit 909af768e88867016f427264ae39d27a57b6a8ed
 .\" commit accb61fe7bb0f5c2a4102239e4981650f9048519
@@ -620,6 +697,11 @@ A kernel resource was temporarily unavailable.
 .B EBADF
 The map exists, but the area maps something that isn't a file.
 .TP
+.B EBUSY
+(for
+.BR MADV_COLLAPSE )
+Could not charge hugepage to cgroup: cgroup limit exceeded.
+.TP
 .B EFAULT
 .I advice
 is
@@ -717,6 +799,11 @@ maximum resident set size.
 Not enough memory: paging in failed.
 .TP
 .B ENOMEM
+(for
+.BR MADV_COLLAPSE )
+Not enough memory: could not allocate hugepage.
+.TP
+.B ENOMEM
 Addresses in the specified range are not currently
 mapped, or are outside the address space of the process.
 .TP
diff --git a/man2/process_madvise.2 b/man2/process_madvise.2
index ac98850a9..92878286b 100644
--- a/man2/process_madvise.2
+++ b/man2/process_madvise.2
@@ -73,6 +73,10 @@ argument is one of the following values:
 See
 .BR madvise (2).
 .TP
+.B MADV_COLLAPSE
+See
+.BR madvise (2).
+.TP
 .B MADV_PAGEOUT
 See
 .BR madvise (2).
@@ -173,6 +177,12 @@ The caller does not have permission to access the address space of the process
 .TP
 .B ESRCH
 The target process does not exist (i.e., it has terminated and been waited on).
+.PP
+See
+.BR madvise (2)
+for
+.IR advice -specific
+errors.
 .SH VERSIONS
 This system call first appeared in Linux 5.10.
 .\" commit ecb8ac8b1f146915aa6b96449b66dd48984caacc
-- 
2.38.1.273.g43a17bfeac-goog

Re: [PATCH man-pages v5] madvise.2: add documentation for MADV_COLLAPSE

[Alejandro Colomar]

[-- Attachment #1.1: Type: text/plain, Size: 7505 bytes --]

Hi Zach!

On 11/1/22 16:03, Zach OKeefe wrote:
> From: Zach O'Keefe <zokeefe@google.com>
> 
> Linux 6.1 introduced MADV_COLLAPSE in upstream commit 7d8faaf15545
> ("mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse") and
> upstream commit 34488399fa08 ("mm/madvise: add file and shmem support to
> MADV_COLLAPSE").  Update the man-pages for madvise(2) and
> process_madvise(2).
> 
> Link: https://lore.kernel.org/linux-mm/20220922224046.1143204-1-zokeefe@google.com/
> Link: https://lore.kernel.org/linux-mm/20220706235936.2197195-1-zokeefe@google.com/
> Signed-off-by: Zach O'Keefe <zokeefe@google.com>

Patch applied.
See a minor edit below for curiosity.
It was very nice to get this patch set improved and applied!

Cheers,

Alex

> ---
> 
> v4[1] -> v5
> - Rebased to latest master
> - (Alejandro Colomar) Applied diff to remove spurious file and fix
>    semantic newlines.
> - (Alejandro Colomar) Reworded documentation describing behavior of
>    setting errno when multiple hugepage-aligned/sized regions fail to
>    collapse.
> 
> v3[2] -> v4
> - Rebased to latest master
> - (Alejandro Colomar) Fixed weird, non-ascii chars: e2 80 99 -> "'"
> - (Alejandro Colomar) Replaced .BR with .B directive when the entire
>    line was bold (no non-bold part)
> 
> [1] https://lore.kernel.org/linux-man/20221031225500.3994542-1-zokeefe@google.com/
> [2] https://lore.kernel.org/linux-man/bb3b5c3c-3966-ea1a-6d84-4f7f3afa37ca@gmail.com/T/#u
> 
>   man2/madvise.2         | 91 +++++++++++++++++++++++++++++++++++++++++-
>   man2/process_madvise.2 | 10 +++++
>   2 files changed, 99 insertions(+), 2 deletions(-)
> 
> diff --git a/man2/madvise.2 b/man2/madvise.2
> index edf805740..038e6023d 100644
> --- a/man2/madvise.2
> +++ b/man2/madvise.2
> @@ -386,9 +386,10 @@ set (see
>   .BR prctl (2)).
>   .IP
>   The
> -.B MADV_HUGEPAGE
> +.BR MADV_HUGEPAGE ,
> +.BR MADV_NOHUGEPAGE ,
>   and
> -.B MADV_NOHUGEPAGE
> +.B MADV_COLLAPSE
>   operations are available only if the kernel was configured with
>   .B CONFIG_TRANSPARENT_HUGEPAGE
>   and file/shmem memory is only supported if the kernel was configured with
> @@ -401,6 +402,82 @@ and
>   .I length
>   will not be backed by transparent hugepages.
>   .TP
> +.BR MADV_COLLAPSE " (since Linux 6.1)"
> +.\" commit 7d8faaf155454f8798ec56404faca29a82689c77
> +.\" commit 34488399fa08faaf664743fa54b271eb6f9e1321
> +Perform a best-effort synchronous collapse of
> +the native pages mapped by the memory range
> +into Transparent Huge Pages (THPs).
> +.B MADV_COLLAPSE
> +operates on the current state of memory of the calling process and
> +makes no persistent changes or guarantees on how pages will be mapped,
> +constructed,
> +or faulted in the future.
> +.IP
> +.B MADV_COLLAPSE
> +supports private anonymous pages (see
> +.BR mmap (2)),
> +shmem pages,
> +and file-backed pages.
> +See
> +.B MADV_HUGEPAGE
> +for general information on memory requirements for THP.
> +If the range provided spans multiple VMAs,
> +the semantics of the collapse over each VMA is independent from the others.
> +If collapse of a given huge page-aligned/sized region fails,
> +the operation may continue to attempt collapsing
> +the remainder of the specified memory.
> +.B MADV_COLLAPSE
> +will automatically clamp the provided range to be hugepage-aligned.
> +.IP
> +All non-resident pages covered by the range
> +will first be swapped/faulted-in,
> +before being copied onto a freshly allocated hugepage.
> +If the native pages compose the same PTE-mapped hugepage,
> +and are suitably aligned,
> +allocation of a new hugepage may be elided and
> +collapse may happen in-place.
> +Unmapped pages will have their data directly initialized to 0
> +in the new hugepage.
> +However,
> +for every eligible hugepage-aligned/sized region to be collapsed,
> +at least one page must currently be backed by physical memory.
> +.IP
> +.B MADV_COLLAPSE
> +is independent of any sysfs
> +(see
> +.BR sysfs (5))
> +setting under
> +.IR /sys/kernel/mm/transparent_hugepage ,
> +both in terms of determining THP eligibility,
> +and allocation semantics.
> +See Linux kernel source file
> +.I Documentation/admin\-guide/mm/transhuge.rst
> +for more information.
> +.B MADV_COLLAPSE
> +also ignores
> +.B huge=
> +tmpfs mount when operating on tmpfs files.
> +Allocation for the new hugepage may enter direct reclaim and/or compaction,
> +regardless of VMA flags
> +(though
> +.B VM_NOHUGEPAGE
> +is still respected).
> +.IP
> +When the system has multiple NUMA nodes,
> +the hugepage will be allocated from
> +the node providing the most native pages.
> +.IP
> +If all hugepage-sized/aligned regions covered by the provided range were
> +either successfully collapsed,
> +or were already PMD-mapped THPs,
> +this operation will be deemed successful.
> +Note that this doesn't guarantee anything about
> +other possible mappings of the memory.
> +In the event multiple hugepage-aligned/sized areas fail to collapse,
> +only the most recently-failed code will be set in

I slightly changed the use of hyphens above with the following diff:

diff --git a/man2/madvise.2 b/man2/madvise.2
index 038e6023d..331465cfc 100644
--- a/man2/madvise.2
+++ b/man2/madvise.2
@@ -475,7 +475,7 @@ .SS Linux-specific advice values
  Note that this doesn't guarantee anything about
  other possible mappings of the memory.
  In the event multiple hugepage-aligned/sized areas fail to collapse,
-only the most recently-failed code will be set in
+only the most-recently\[en]failed code will be set in
  .IR errno .
  .TP
  .BR MADV_DONTDUMP " (since Linux 3.4)"


Rationale:
<https://lists.gnu.org/archive/html/groff/2022-10/msg00019.html>


> +.IR errno .
> +.TP
>   .BR MADV_DONTDUMP " (since Linux 3.4)"
>   .\" commit 909af768e88867016f427264ae39d27a57b6a8ed
>   .\" commit accb61fe7bb0f5c2a4102239e4981650f9048519
> @@ -620,6 +697,11 @@ A kernel resource was temporarily unavailable.
>   .B EBADF
>   The map exists, but the area maps something that isn't a file.
>   .TP
> +.B EBUSY
> +(for
> +.BR MADV_COLLAPSE )
> +Could not charge hugepage to cgroup: cgroup limit exceeded.
> +.TP
>   .B EFAULT
>   .I advice
>   is
> @@ -717,6 +799,11 @@ maximum resident set size.
>   Not enough memory: paging in failed.
>   .TP
>   .B ENOMEM
> +(for
> +.BR MADV_COLLAPSE )
> +Not enough memory: could not allocate hugepage.
> +.TP
> +.B ENOMEM
>   Addresses in the specified range are not currently
>   mapped, or are outside the address space of the process.
>   .TP
> diff --git a/man2/process_madvise.2 b/man2/process_madvise.2
> index ac98850a9..92878286b 100644
> --- a/man2/process_madvise.2
> +++ b/man2/process_madvise.2
> @@ -73,6 +73,10 @@ argument is one of the following values:
>   See
>   .BR madvise (2).
>   .TP
> +.B MADV_COLLAPSE
> +See
> +.BR madvise (2).
> +.TP
>   .B MADV_PAGEOUT
>   See
>   .BR madvise (2).
> @@ -173,6 +177,12 @@ The caller does not have permission to access the address space of the process
>   .TP
>   .B ESRCH
>   The target process does not exist (i.e., it has terminated and been waited on).
> +.PP
> +See
> +.BR madvise (2)
> +for
> +.IR advice -specific
> +errors.
>   .SH VERSIONS
>   This system call first appeared in Linux 5.10.
>   .\" commit ecb8ac8b1f146915aa6b96449b66dd48984caacc

-- 
<http://www.alejandro-colomar.es/>

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Re: [PATCH man-pages v5] madvise.2: add documentation for MADV_COLLAPSE

[Zach O'Keefe]

Hey Alex!

On Tue, Nov 1, 2022 at 8:47 AM Alejandro Colomar <alx.manpages@gmail.com> wrote:
>
> Hi Zach!
>
> On 11/1/22 16:03, Zach OKeefe wrote:
> > From: Zach O'Keefe <zokeefe@google.com>
> >
> > Linux 6.1 introduced MADV_COLLAPSE in upstream commit 7d8faaf15545
> > ("mm/madvise: introduce MADV_COLLAPSE sync hugepage collapse") and
> > upstream commit 34488399fa08 ("mm/madvise: add file and shmem support to
> > MADV_COLLAPSE").  Update the man-pages for madvise(2) and
> > process_madvise(2).
> >
> > Link: https://lore.kernel.org/linux-mm/20220922224046.1143204-1-zokeefe@google.com/
> > Link: https://lore.kernel.org/linux-mm/20220706235936.2197195-1-zokeefe@google.com/
> > Signed-off-by: Zach O'Keefe <zokeefe@google.com>
>
> Patch applied.
> See a minor edit below for curiosity.
> It was very nice to get this patch set improved and applied!
>

Awesome! Very excited to see it in :)

> Cheers,
>
> Alex
>
> > ---
> >
> > v4[1] -> v5
> > - Rebased to latest master
> > - (Alejandro Colomar) Applied diff to remove spurious file and fix
> >    semantic newlines.
> > - (Alejandro Colomar) Reworded documentation describing behavior of
> >    setting errno when multiple hugepage-aligned/sized regions fail to
> >    collapse.
> >
> > v3[2] -> v4
> > - Rebased to latest master
> > - (Alejandro Colomar) Fixed weird, non-ascii chars: e2 80 99 -> "'"
> > - (Alejandro Colomar) Replaced .BR with .B directive when the entire
> >    line was bold (no non-bold part)
> >
> > [1] https://lore.kernel.org/linux-man/20221031225500.3994542-1-zokeefe@google.com/
> > [2] https://lore.kernel.org/linux-man/bb3b5c3c-3966-ea1a-6d84-4f7f3afa37ca@gmail.com/T/#u
> >
> >   man2/madvise.2         | 91 +++++++++++++++++++++++++++++++++++++++++-
> >   man2/process_madvise.2 | 10 +++++
> >   2 files changed, 99 insertions(+), 2 deletions(-)
> >
> > diff --git a/man2/madvise.2 b/man2/madvise.2
> > index edf805740..038e6023d 100644
> > --- a/man2/madvise.2
> > +++ b/man2/madvise.2
> > @@ -386,9 +386,10 @@ set (see
> >   .BR prctl (2)).
> >   .IP
> >   The
> > -.B MADV_HUGEPAGE
> > +.BR MADV_HUGEPAGE ,
> > +.BR MADV_NOHUGEPAGE ,
> >   and
> > -.B MADV_NOHUGEPAGE
> > +.B MADV_COLLAPSE
> >   operations are available only if the kernel was configured with
> >   .B CONFIG_TRANSPARENT_HUGEPAGE
> >   and file/shmem memory is only supported if the kernel was configured with
> > @@ -401,6 +402,82 @@ and
> >   .I length
> >   will not be backed by transparent hugepages.
> >   .TP
> > +.BR MADV_COLLAPSE " (since Linux 6.1)"
> > +.\" commit 7d8faaf155454f8798ec56404faca29a82689c77
> > +.\" commit 34488399fa08faaf664743fa54b271eb6f9e1321
> > +Perform a best-effort synchronous collapse of
> > +the native pages mapped by the memory range
> > +into Transparent Huge Pages (THPs).
> > +.B MADV_COLLAPSE
> > +operates on the current state of memory of the calling process and
> > +makes no persistent changes or guarantees on how pages will be mapped,
> > +constructed,
> > +or faulted in the future.
> > +.IP
> > +.B MADV_COLLAPSE
> > +supports private anonymous pages (see
> > +.BR mmap (2)),
> > +shmem pages,
> > +and file-backed pages.
> > +See
> > +.B MADV_HUGEPAGE
> > +for general information on memory requirements for THP.
> > +If the range provided spans multiple VMAs,
> > +the semantics of the collapse over each VMA is independent from the others.
> > +If collapse of a given huge page-aligned/sized region fails,
> > +the operation may continue to attempt collapsing
> > +the remainder of the specified memory.
> > +.B MADV_COLLAPSE
> > +will automatically clamp the provided range to be hugepage-aligned.
> > +.IP
> > +All non-resident pages covered by the range
> > +will first be swapped/faulted-in,
> > +before being copied onto a freshly allocated hugepage.
> > +If the native pages compose the same PTE-mapped hugepage,
> > +and are suitably aligned,
> > +allocation of a new hugepage may be elided and
> > +collapse may happen in-place.
> > +Unmapped pages will have their data directly initialized to 0
> > +in the new hugepage.
> > +However,
> > +for every eligible hugepage-aligned/sized region to be collapsed,
> > +at least one page must currently be backed by physical memory.
> > +.IP
> > +.B MADV_COLLAPSE
> > +is independent of any sysfs
> > +(see
> > +.BR sysfs (5))
> > +setting under
> > +.IR /sys/kernel/mm/transparent_hugepage ,
> > +both in terms of determining THP eligibility,
> > +and allocation semantics.
> > +See Linux kernel source file
> > +.I Documentation/admin\-guide/mm/transhuge.rst
> > +for more information.
> > +.B MADV_COLLAPSE
> > +also ignores
> > +.B huge=
> > +tmpfs mount when operating on tmpfs files.
> > +Allocation for the new hugepage may enter direct reclaim and/or compaction,
> > +regardless of VMA flags
> > +(though
> > +.B VM_NOHUGEPAGE
> > +is still respected).
> > +.IP
> > +When the system has multiple NUMA nodes,
> > +the hugepage will be allocated from
> > +the node providing the most native pages.
> > +.IP
> > +If all hugepage-sized/aligned regions covered by the provided range were
> > +either successfully collapsed,
> > +or were already PMD-mapped THPs,
> > +this operation will be deemed successful.
> > +Note that this doesn't guarantee anything about
> > +other possible mappings of the memory.
> > +In the event multiple hugepage-aligned/sized areas fail to collapse,
> > +only the most recently-failed code will be set in
>
> I slightly changed the use of hyphens above with the following diff:
>
> diff --git a/man2/madvise.2 b/man2/madvise.2
> index 038e6023d..331465cfc 100644
> --- a/man2/madvise.2
> +++ b/man2/madvise.2
> @@ -475,7 +475,7 @@ .SS Linux-specific advice values
>   Note that this doesn't guarantee anything about
>   other possible mappings of the memory.
>   In the event multiple hugepage-aligned/sized areas fail to collapse,
> -only the most recently-failed code will be set in
> +only the most-recently\[en]failed code will be set in
>   .IR errno .
>   .TP
>   .BR MADV_DONTDUMP " (since Linux 3.4)"
>
>
> Rationale:
> <https://lists.gnu.org/archive/html/groff/2022-10/msg00019.html>
>

Appreciate the change, and thanks for the link -- very subtle. The
differences between various dashes (which I was only made aware of by
yourself) is still a little unclear to me.

Again, thank you so much for your patience and help throughout this
process -- I really appreciate it.

Best,
Zach

>
> > +.IR errno .
> > +.TP
> >   .BR MADV_DONTDUMP " (since Linux 3.4)"
> >   .\" commit 909af768e88867016f427264ae39d27a57b6a8ed
> >   .\" commit accb61fe7bb0f5c2a4102239e4981650f9048519
> > @@ -620,6 +697,11 @@ A kernel resource was temporarily unavailable.
> >   .B EBADF
> >   The map exists, but the area maps something that isn't a file.
> >   .TP
> > +.B EBUSY
> > +(for
> > +.BR MADV_COLLAPSE )
> > +Could not charge hugepage to cgroup: cgroup limit exceeded.
> > +.TP
> >   .B EFAULT
> >   .I advice
> >   is
> > @@ -717,6 +799,11 @@ maximum resident set size.
> >   Not enough memory: paging in failed.
> >   .TP
> >   .B ENOMEM
> > +(for
> > +.BR MADV_COLLAPSE )
> > +Not enough memory: could not allocate hugepage.
> > +.TP
> > +.B ENOMEM
> >   Addresses in the specified range are not currently
> >   mapped, or are outside the address space of the process.
> >   .TP
> > diff --git a/man2/process_madvise.2 b/man2/process_madvise.2
> > index ac98850a9..92878286b 100644
> > --- a/man2/process_madvise.2
> > +++ b/man2/process_madvise.2
> > @@ -73,6 +73,10 @@ argument is one of the following values:
> >   See
> >   .BR madvise (2).
> >   .TP
> > +.B MADV_COLLAPSE
> > +See
> > +.BR madvise (2).
> > +.TP
> >   .B MADV_PAGEOUT
> >   See
> >   .BR madvise (2).
> > @@ -173,6 +177,12 @@ The caller does not have permission to access the address space of the process
> >   .TP
> >   .B ESRCH
> >   The target process does not exist (i.e., it has terminated and been waited on).
> > +.PP
> > +See
> > +.BR madvise (2)
> > +for
> > +.IR advice -specific
> > +errors.
> >   .SH VERSIONS
> >   This system call first appeared in Linux 5.10.
> >   .\" commit ecb8ac8b1f146915aa6b96449b66dd48984caacc
>
> --
> <http://www.alejandro-colomar.es/>