* [PATCH v5 00/12] MADV_FREE support
@ 2015-11-30 6:39 Minchan Kim
2016-01-28 7:16 ` Michael Kerrisk (man-pages)
0 siblings, 1 reply; 6+ messages in thread
From: Minchan Kim @ 2015-11-30 6:39 UTC (permalink / raw)
To: Andrew Morton
Cc: linux-kernel, linux-mm, Michael Kerrisk, linux-api, Hugh Dickins,
Johannes Weiner, Rik van Riel, Mel Gorman, KOSAKI Motohiro,
Jason Evans, Daniel Micay, Kirill A. Shutemov, Shaohua Li,
Michal Hocko, yalin.wang2010, Andy Lutomirski, Minchan Kim
In v4, Andrew wanted to settle in old basic MADV_FREE and introduces
new stuffs(ie, lazyfree LRU, swapless support and lazyfreeness) later
so this version doesn't include them.
I have been tested it on mmotm-2015-11-25-17-08 with additional
patch[1] from Kirill to prevent BUG_ON which he didn't send to
linux-mm yet as formal patch. With it, I couldn't find any
problem so far.
Note that this version is based on THP refcount redesign so
I needed some modification on MADV_FREE because split_huge_pmd
doesn't split a THP page any more and pmd_trans_huge(pmd) is not
enough to guarantee the page is not THP page.
As well, for MAVD_FREE lazy-split, THP split should respect
pmd's dirtiness rather than marking ptes of all subpages dirty
unconditionally. Please, review last patch in this patchset.
mm: don't split THP page when syscall is called
[1] https://lkml.org/lkml/2015/11/17/134
git: git://git.kernel.org/pub/scm/linux/kernel/git/minchan/linux.git
branch: mm/madv_free-v4.4-rc2-mmotm-2015-11-25-17-08-v5r2
In this stage, I don't think we need to write man page.
It could be done after solid policy and implementation.
* Change from v4
* drop lazyfree LRU
* drop swapless support
* drop lazyfreeness
* rebase on recent mmotom with THP refcount redesign
* Change from v3
* some bug fix
* code refactoring
* lazyfree reclaim logic change
* reordering patch
* Change from v2
* vm_lazyfreeness tuning knob
* add new LRU list - Johannes, Shaohua
* support swapless - Johannes
* Change from v1
* Don't do unnecessary TLB flush - Shaohua
* Added Acked-by - Hugh, Michal
* Merge deactivate_page and deactivate_file_page
* Add pmd_dirty/pmd_mkclean patches for several arches
* Add lazy THP split patch
* Drop zhangyanfei@cn.fujitsu.com - Delivery Failure
Chen Gang (1):
arch: uapi: asm: mman.h: Let MADV_FREE have same value for all
architectures
Minchan Kim (11):
mm: support madvise(MADV_FREE)
mm: define MADV_FREE for some arches
mm: free swp_entry in madvise_free
mm: move lazily freed pages to inactive list
mm: mark stable page dirty in KSM
x86: add pmd_[dirty|mkclean] for THP
sparc: add pmd_[dirty|mkclean] for THP
powerpc: add pmd_[dirty|mkclean] for THP
arm: add pmd_mkclean for THP
arm64: add pmd_mkclean for THP
mm: don't split THP page when syscall is called
arch/alpha/include/uapi/asm/mman.h | 2 +
arch/arm/include/asm/pgtable-3level.h | 1 +
arch/arm64/include/asm/pgtable.h | 1 +
arch/mips/include/uapi/asm/mman.h | 2 +
arch/parisc/include/uapi/asm/mman.h | 2 +
arch/powerpc/include/asm/pgtable-ppc64.h | 2 +
arch/sparc/include/asm/pgtable_64.h | 9 ++
arch/x86/include/asm/pgtable.h | 5 +
arch/xtensa/include/uapi/asm/mman.h | 2 +
include/linux/huge_mm.h | 3 +
include/linux/rmap.h | 1 +
include/linux/swap.h | 1 +
include/linux/vm_event_item.h | 1 +
include/uapi/asm-generic/mman-common.h | 1 +
mm/huge_memory.c | 87 +++++++++++++-
mm/ksm.c | 6 +
mm/madvise.c | 199 +++++++++++++++++++++++++++++++
mm/rmap.c | 8 ++
mm/swap.c | 44 +++++++
mm/swap_state.c | 5 +-
mm/vmscan.c | 10 +-
mm/vmstat.c | 1 +
22 files changed, 383 insertions(+), 10 deletions(-)
--
1.9.1
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v5 00/12] MADV_FREE support
2015-11-30 6:39 Minchan Kim
@ 2016-01-28 7:16 ` Michael Kerrisk (man-pages)
2016-01-29 7:32 ` Minchan Kim
0 siblings, 1 reply; 6+ messages in thread
From: Michael Kerrisk (man-pages) @ 2016-01-28 7:16 UTC (permalink / raw)
To: Minchan Kim, Andrew Morton
Cc: mtk.manpages, linux-kernel, linux-mm, linux-api, Hugh Dickins,
Johannes Weiner, Rik van Riel, Mel Gorman, KOSAKI Motohiro,
Jason Evans, Daniel Micay, Kirill A. Shutemov, Shaohua Li,
Michal Hocko, yalin.wang2010, Andy Lutomirski
Hello Minchan,
On 11/30/2015 07:39 AM, Minchan Kim wrote:
> In v4, Andrew wanted to settle in old basic MADV_FREE and introduces
> new stuffs(ie, lazyfree LRU, swapless support and lazyfreeness) later
> so this version doesn't include them.
>
> I have been tested it on mmotm-2015-11-25-17-08 with additional
> patch[1] from Kirill to prevent BUG_ON which he didn't send to
> linux-mm yet as formal patch. With it, I couldn't find any
> problem so far.
>
> Note that this version is based on THP refcount redesign so
> I needed some modification on MADV_FREE because split_huge_pmd
> doesn't split a THP page any more and pmd_trans_huge(pmd) is not
> enough to guarantee the page is not THP page.
> As well, for MAVD_FREE lazy-split, THP split should respect
> pmd's dirtiness rather than marking ptes of all subpages dirty
> unconditionally. Please, review last patch in this patchset.
Now that MADV_FREE has been merged, would you be willing to write
patch to the madvise(2) man page that describes the semantics,
noes limitations and restrictions, and (ideally) has some sentences
describing use cases?
Thanks,
Michael
> mm: don't split THP page when syscall is called
>
> [1] https://lkml.org/lkml/2015/11/17/134
>
> git: git://git.kernel.org/pub/scm/linux/kernel/git/minchan/linux.git
> branch: mm/madv_free-v4.4-rc2-mmotm-2015-11-25-17-08-v5r2
>
> In this stage, I don't think we need to write man page.
> It could be done after solid policy and implementation.
>
> * Change from v4
> * drop lazyfree LRU
> * drop swapless support
> * drop lazyfreeness
> * rebase on recent mmotom with THP refcount redesign
>
> * Change from v3
> * some bug fix
> * code refactoring
> * lazyfree reclaim logic change
> * reordering patch
>
> * Change from v2
> * vm_lazyfreeness tuning knob
> * add new LRU list - Johannes, Shaohua
> * support swapless - Johannes
>
> * Change from v1
> * Don't do unnecessary TLB flush - Shaohua
> * Added Acked-by - Hugh, Michal
> * Merge deactivate_page and deactivate_file_page
> * Add pmd_dirty/pmd_mkclean patches for several arches
> * Add lazy THP split patch
> * Drop zhangyanfei@cn.fujitsu.com - Delivery Failure
>
> Chen Gang (1):
> arch: uapi: asm: mman.h: Let MADV_FREE have same value for all
> architectures
>
> Minchan Kim (11):
> mm: support madvise(MADV_FREE)
> mm: define MADV_FREE for some arches
> mm: free swp_entry in madvise_free
> mm: move lazily freed pages to inactive list
> mm: mark stable page dirty in KSM
> x86: add pmd_[dirty|mkclean] for THP
> sparc: add pmd_[dirty|mkclean] for THP
> powerpc: add pmd_[dirty|mkclean] for THP
> arm: add pmd_mkclean for THP
> arm64: add pmd_mkclean for THP
> mm: don't split THP page when syscall is called
>
> arch/alpha/include/uapi/asm/mman.h | 2 +
> arch/arm/include/asm/pgtable-3level.h | 1 +
> arch/arm64/include/asm/pgtable.h | 1 +
> arch/mips/include/uapi/asm/mman.h | 2 +
> arch/parisc/include/uapi/asm/mman.h | 2 +
> arch/powerpc/include/asm/pgtable-ppc64.h | 2 +
> arch/sparc/include/asm/pgtable_64.h | 9 ++
> arch/x86/include/asm/pgtable.h | 5 +
> arch/xtensa/include/uapi/asm/mman.h | 2 +
> include/linux/huge_mm.h | 3 +
> include/linux/rmap.h | 1 +
> include/linux/swap.h | 1 +
> include/linux/vm_event_item.h | 1 +
> include/uapi/asm-generic/mman-common.h | 1 +
> mm/huge_memory.c | 87 +++++++++++++-
> mm/ksm.c | 6 +
> mm/madvise.c | 199 +++++++++++++++++++++++++++++++
> mm/rmap.c | 8 ++
> mm/swap.c | 44 +++++++
> mm/swap_state.c | 5 +-
> mm/vmscan.c | 10 +-
> mm/vmstat.c | 1 +
> 22 files changed, 383 insertions(+), 10 deletions(-)
>
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v5 00/12] MADV_FREE support
2016-01-28 7:16 ` Michael Kerrisk (man-pages)
@ 2016-01-29 7:32 ` Minchan Kim
0 siblings, 0 replies; 6+ messages in thread
From: Minchan Kim @ 2016-01-29 7:32 UTC (permalink / raw)
To: Michael Kerrisk (man-pages)
Cc: Andrew Morton, linux-kernel, linux-mm, linux-api, Hugh Dickins,
Johannes Weiner, Rik van Riel, Mel Gorman, KOSAKI Motohiro,
Jason Evans, Daniel Micay, Kirill A. Shutemov, Shaohua Li,
Michal Hocko, yalin.wang2010, Andy Lutomirski
Hello Michael,
On Thu, Jan 28, 2016 at 08:16:25AM +0100, Michael Kerrisk (man-pages) wrote:
> Hello Minchan,
>
> On 11/30/2015 07:39 AM, Minchan Kim wrote:
> > In v4, Andrew wanted to settle in old basic MADV_FREE and introduces
> > new stuffs(ie, lazyfree LRU, swapless support and lazyfreeness) later
> > so this version doesn't include them.
> >
> > I have been tested it on mmotm-2015-11-25-17-08 with additional
> > patch[1] from Kirill to prevent BUG_ON which he didn't send to
> > linux-mm yet as formal patch. With it, I couldn't find any
> > problem so far.
> >
> > Note that this version is based on THP refcount redesign so
> > I needed some modification on MADV_FREE because split_huge_pmd
> > doesn't split a THP page any more and pmd_trans_huge(pmd) is not
> > enough to guarantee the page is not THP page.
> > As well, for MAVD_FREE lazy-split, THP split should respect
> > pmd's dirtiness rather than marking ptes of all subpages dirty
> > unconditionally. Please, review last patch in this patchset.
>
> Now that MADV_FREE has been merged, would you be willing to write
> patch to the madvise(2) man page that describes the semantics,
> noes limitations and restrictions, and (ideally) has some sentences
> describing use cases?
I will try next week.
Thanks for the heads up.
>
> Thanks,
>
> Michael
>
>
> > mm: don't split THP page when syscall is called
> >
> > [1] https://lkml.org/lkml/2015/11/17/134
> >
> > git: git://git.kernel.org/pub/scm/linux/kernel/git/minchan/linux.git
> > branch: mm/madv_free-v4.4-rc2-mmotm-2015-11-25-17-08-v5r2
> >
> > In this stage, I don't think we need to write man page.
> > It could be done after solid policy and implementation.
> >
> > * Change from v4
> > * drop lazyfree LRU
> > * drop swapless support
> > * drop lazyfreeness
> > * rebase on recent mmotom with THP refcount redesign
> >
> > * Change from v3
> > * some bug fix
> > * code refactoring
> > * lazyfree reclaim logic change
> > * reordering patch
> >
> > * Change from v2
> > * vm_lazyfreeness tuning knob
> > * add new LRU list - Johannes, Shaohua
> > * support swapless - Johannes
> >
> > * Change from v1
> > * Don't do unnecessary TLB flush - Shaohua
> > * Added Acked-by - Hugh, Michal
> > * Merge deactivate_page and deactivate_file_page
> > * Add pmd_dirty/pmd_mkclean patches for several arches
> > * Add lazy THP split patch
> > * Drop zhangyanfei@cn.fujitsu.com - Delivery Failure
> >
> > Chen Gang (1):
> > arch: uapi: asm: mman.h: Let MADV_FREE have same value for all
> > architectures
> >
> > Minchan Kim (11):
> > mm: support madvise(MADV_FREE)
> > mm: define MADV_FREE for some arches
> > mm: free swp_entry in madvise_free
> > mm: move lazily freed pages to inactive list
> > mm: mark stable page dirty in KSM
> > x86: add pmd_[dirty|mkclean] for THP
> > sparc: add pmd_[dirty|mkclean] for THP
> > powerpc: add pmd_[dirty|mkclean] for THP
> > arm: add pmd_mkclean for THP
> > arm64: add pmd_mkclean for THP
> > mm: don't split THP page when syscall is called
> >
> > arch/alpha/include/uapi/asm/mman.h | 2 +
> > arch/arm/include/asm/pgtable-3level.h | 1 +
> > arch/arm64/include/asm/pgtable.h | 1 +
> > arch/mips/include/uapi/asm/mman.h | 2 +
> > arch/parisc/include/uapi/asm/mman.h | 2 +
> > arch/powerpc/include/asm/pgtable-ppc64.h | 2 +
> > arch/sparc/include/asm/pgtable_64.h | 9 ++
> > arch/x86/include/asm/pgtable.h | 5 +
> > arch/xtensa/include/uapi/asm/mman.h | 2 +
> > include/linux/huge_mm.h | 3 +
> > include/linux/rmap.h | 1 +
> > include/linux/swap.h | 1 +
> > include/linux/vm_event_item.h | 1 +
> > include/uapi/asm-generic/mman-common.h | 1 +
> > mm/huge_memory.c | 87 +++++++++++++-
> > mm/ksm.c | 6 +
> > mm/madvise.c | 199 +++++++++++++++++++++++++++++++
> > mm/rmap.c | 8 ++
> > mm/swap.c | 44 +++++++
> > mm/swap_state.c | 5 +-
> > mm/vmscan.c | 10 +-
> > mm/vmstat.c | 1 +
> > 22 files changed, 383 insertions(+), 10 deletions(-)
> >
>
>
> --
> Michael Kerrisk
> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> Linux/UNIX System Programming Training: http://man7.org/training/
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v5 00/12] MADV_FREE support
@ 2016-02-05 2:15 Minchan Kim
2016-02-06 13:32 ` Michael Kerrisk (man-pages)
0 siblings, 1 reply; 6+ messages in thread
From: Minchan Kim @ 2016-02-05 2:15 UTC (permalink / raw)
To: Michael Kerrisk (man-pages)
Cc: Andrew Morton, linux-kernel, linux-mm, linux-api, Hugh Dickins,
Johannes Weiner, Rik van Riel, Mel Gorman, KOSAKI Motohiro,
Jason Evans, Daniel Micay, Kirill A. Shutemov, Shaohua Li,
Michal Hocko, yalin.wang2010, Andy Lutomirski
On Thu, Jan 28, 2016 at 08:16:25AM +0100, Michael Kerrisk (man-pages) wrote:
> Hello Minchan,
>
> On 11/30/2015 07:39 AM, Minchan Kim wrote:
> > In v4, Andrew wanted to settle in old basic MADV_FREE and introduces
> > new stuffs(ie, lazyfree LRU, swapless support and lazyfreeness) later
> > so this version doesn't include them.
> >
> > I have been tested it on mmotm-2015-11-25-17-08 with additional
> > patch[1] from Kirill to prevent BUG_ON which he didn't send to
> > linux-mm yet as formal patch. With it, I couldn't find any
> > problem so far.
> >
> > Note that this version is based on THP refcount redesign so
> > I needed some modification on MADV_FREE because split_huge_pmd
> > doesn't split a THP page any more and pmd_trans_huge(pmd) is not
> > enough to guarantee the page is not THP page.
> > As well, for MAVD_FREE lazy-split, THP split should respect
> > pmd's dirtiness rather than marking ptes of all subpages dirty
> > unconditionally. Please, review last patch in this patchset.
>
> Now that MADV_FREE has been merged, would you be willing to write
> patch to the madvise(2) man page that describes the semantics,
> noes limitations and restrictions, and (ideally) has some sentences
> describing use cases?
>
Hello Michael,
Could you review this patch?
Thanks.
>From 203372f901f574e991215fdff6907608ba53f932 Mon Sep 17 00:00:00 2001
From: Minchan Kim <minchan@kernel.org>
Date: Fri, 5 Feb 2016 11:09:54 +0900
Subject: [PATCH] madvise.2: Add MADV_FREE
Document the MADV_FREE flags added to madvise() in Linux 4.5
Signed-off-by: Minchan Kim <minchan@kernel.org>
---
man2/madvise.2 | 19 +++++++++++++++++++
1 file changed, 19 insertions(+)
diff --git a/man2/madvise.2 b/man2/madvise.2
index c1df67c..4704304 100644
--- a/man2/madvise.2
+++ b/man2/madvise.2
@@ -143,6 +143,25 @@ flag are special memory areas that are not managed
by the virtual memory subsystem.
Such pages are typically created by device drivers that
map the pages into user space.)
+.TP
+.B MADV_FREE " (since Linux 4.5)"
+Application is finished with the given range, so kernel can free
+resources associated with it but the freeing could be delayed until
+memory pressure happens or canceld by write operation by user.
+
+After a successful MADV_FREE operation, user shouldn't expect kernel
+keeps stale data on the page. However, subsequent write of pages
+in the range will succeed and then kernel cannot free those dirtied pages
+so user can always see just written data. If there was no subsequent
+write, kernel can free those clean pages any time. In such case,
+user can see zero-fill-on-demand pages.
+
+Note that, it works only with private anonymous pages (see
+.BR mmap (2)).
+On swapless system, freeing pages in given range happens instantly
+regardless of memory pressure.
+
+
.\"
.\" ======================================================================
.\"
--
1.9.1
^ permalink raw reply related [flat|nested] 6+ messages in thread
* Re: [PATCH v5 00/12] MADV_FREE support
2016-02-05 2:15 [PATCH v5 00/12] MADV_FREE support Minchan Kim
@ 2016-02-06 13:32 ` Michael Kerrisk (man-pages)
2016-02-07 12:31 ` Minchan Kim
0 siblings, 1 reply; 6+ messages in thread
From: Michael Kerrisk (man-pages) @ 2016-02-06 13:32 UTC (permalink / raw)
To: Minchan Kim
Cc: mtk.manpages, Andrew Morton, linux-kernel, linux-mm, linux-api,
Hugh Dickins, Johannes Weiner, Rik van Riel, Mel Gorman,
KOSAKI Motohiro, Jason Evans, Daniel Micay, Kirill A. Shutemov,
Shaohua Li, Michal Hocko, yalin.wang2010, Andy Lutomirski
Hello Minchan,
On 02/05/2016 03:15 AM, Minchan Kim wrote:
> On Thu, Jan 28, 2016 at 08:16:25AM +0100, Michael Kerrisk (man-pages) wrote:
>> Hello Minchan,
>>
>> On 11/30/2015 07:39 AM, Minchan Kim wrote:
>>> In v4, Andrew wanted to settle in old basic MADV_FREE and introduces
>>> new stuffs(ie, lazyfree LRU, swapless support and lazyfreeness) later
>>> so this version doesn't include them.
>>>
>>> I have been tested it on mmotm-2015-11-25-17-08 with additional
>>> patch[1] from Kirill to prevent BUG_ON which he didn't send to
>>> linux-mm yet as formal patch. With it, I couldn't find any
>>> problem so far.
>>>
>>> Note that this version is based on THP refcount redesign so
>>> I needed some modification on MADV_FREE because split_huge_pmd
>>> doesn't split a THP page any more and pmd_trans_huge(pmd) is not
>>> enough to guarantee the page is not THP page.
>>> As well, for MAVD_FREE lazy-split, THP split should respect
>>> pmd's dirtiness rather than marking ptes of all subpages dirty
>>> unconditionally. Please, review last patch in this patchset.
>>
>> Now that MADV_FREE has been merged, would you be willing to write
>> patch to the madvise(2) man page that describes the semantics,
>> noes limitations and restrictions, and (ideally) has some sentences
>> describing use cases?
>>
>
> Hello Michael,
>
> Could you review this patch?
>
> Thanks.
>
>>From 203372f901f574e991215fdff6907608ba53f932 Mon Sep 17 00:00:00 2001
> From: Minchan Kim <minchan@kernel.org>
> Date: Fri, 5 Feb 2016 11:09:54 +0900
> Subject: [PATCH] madvise.2: Add MADV_FREE
>
> Document the MADV_FREE flags added to madvise() in Linux 4.5
>
> Signed-off-by: Minchan Kim <minchan@kernel.org>
> ---
> man2/madvise.2 | 19 +++++++++++++++++++
> 1 file changed, 19 insertions(+)
>
> diff --git a/man2/madvise.2 b/man2/madvise.2
> index c1df67c..4704304 100644
> --- a/man2/madvise.2
> +++ b/man2/madvise.2
> @@ -143,6 +143,25 @@ flag are special memory areas that are not managed
> by the virtual memory subsystem.
> Such pages are typically created by device drivers that
> map the pages into user space.)
> +.TP
> +.B MADV_FREE " (since Linux 4.5)"
> +Application is finished with the given range, so kernel can free
> +resources associated with it but the freeing could be delayed until
> +memory pressure happens or canceld by write operation by user.
> +
> +After a successful MADV_FREE operation, user shouldn't expect kernel
> +keeps stale data on the page. However, subsequent write of pages
> +in the range will succeed and then kernel cannot free those dirtied pages
> +so user can always see just written data. If there was no subsequent
> +write, kernel can free those clean pages any time. In such case,
> +user can see zero-fill-on-demand pages.
> +
> +Note that, it works only with private anonymous pages (see
> +.BR mmap (2)).
> +On swapless system, freeing pages in given range happens instantly
> +regardless of memory pressure.
> +
> +
> .\"
> .\" ======================================================================
> .\"
>
Thanks for the nice text! I reworked somewhat, trying to fill out a
few details about how I understand things work, but I may have introduced
errors, so I would be happy if you would check the following text:
MADV_FREE (since Linux 4.5)
The application no longer requires the pages in the
range specified by addr and len. The kernel can thus
free these pages, but the freeing could be delayed until
memory pressure occurs. For each of the pages that has
been marked to be freed but has not yet been freed, the
free operation will be canceled if the caller writes
into the page. After a successful MADV_FREE operation,
any stale data (i.e., dirty, unwritten pages) will be
lost when the kernel frees the pages. However, subse‐
quent writes to pages in the range will succeed and then
kernel cannot free those dirtied pages, so that the
caller can always see just written data. If there is no
subsequent write, the kernel can free the pages at any
time. Once pages in the range have been freed, the
caller will see zero-fill-on-demand pages upon subse‐
quent page references.
The MADV_FREE operation can be applied only to private
anonymous pages (see mmap(2)). On a swapless system,
freeing pages in a given range happens instantly,
regardless of memory pressure.
Thanks,
Michael
--
Michael Kerrisk
Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
Linux/UNIX System Programming Training: http://man7.org/training/
^ permalink raw reply [flat|nested] 6+ messages in thread
* Re: [PATCH v5 00/12] MADV_FREE support
2016-02-06 13:32 ` Michael Kerrisk (man-pages)
@ 2016-02-07 12:31 ` Minchan Kim
0 siblings, 0 replies; 6+ messages in thread
From: Minchan Kim @ 2016-02-07 12:31 UTC (permalink / raw)
To: Michael Kerrisk (man-pages)
Cc: Andrew Morton, linux-kernel, linux-mm, linux-api, Hugh Dickins,
Johannes Weiner, Rik van Riel, Mel Gorman, KOSAKI Motohiro,
Jason Evans, Daniel Micay, Kirill A. Shutemov, Shaohua Li,
Michal Hocko, yalin.wang2010, Andy Lutomirski
On Sat, Feb 06, 2016 at 02:32:02PM +0100, Michael Kerrisk (man-pages) wrote:
> Hello Minchan,
>
> On 02/05/2016 03:15 AM, Minchan Kim wrote:
> > On Thu, Jan 28, 2016 at 08:16:25AM +0100, Michael Kerrisk (man-pages) wrote:
> >> Hello Minchan,
> >>
> >> On 11/30/2015 07:39 AM, Minchan Kim wrote:
> >>> In v4, Andrew wanted to settle in old basic MADV_FREE and introduces
> >>> new stuffs(ie, lazyfree LRU, swapless support and lazyfreeness) later
> >>> so this version doesn't include them.
> >>>
> >>> I have been tested it on mmotm-2015-11-25-17-08 with additional
> >>> patch[1] from Kirill to prevent BUG_ON which he didn't send to
> >>> linux-mm yet as formal patch. With it, I couldn't find any
> >>> problem so far.
> >>>
> >>> Note that this version is based on THP refcount redesign so
> >>> I needed some modification on MADV_FREE because split_huge_pmd
> >>> doesn't split a THP page any more and pmd_trans_huge(pmd) is not
> >>> enough to guarantee the page is not THP page.
> >>> As well, for MAVD_FREE lazy-split, THP split should respect
> >>> pmd's dirtiness rather than marking ptes of all subpages dirty
> >>> unconditionally. Please, review last patch in this patchset.
> >>
> >> Now that MADV_FREE has been merged, would you be willing to write
> >> patch to the madvise(2) man page that describes the semantics,
> >> noes limitations and restrictions, and (ideally) has some sentences
> >> describing use cases?
> >>
> >
> > Hello Michael,
> >
> > Could you review this patch?
> >
> > Thanks.
> >
> >>From 203372f901f574e991215fdff6907608ba53f932 Mon Sep 17 00:00:00 2001
> > From: Minchan Kim <minchan@kernel.org>
> > Date: Fri, 5 Feb 2016 11:09:54 +0900
> > Subject: [PATCH] madvise.2: Add MADV_FREE
> >
> > Document the MADV_FREE flags added to madvise() in Linux 4.5
> >
> > Signed-off-by: Minchan Kim <minchan@kernel.org>
> > ---
> > man2/madvise.2 | 19 +++++++++++++++++++
> > 1 file changed, 19 insertions(+)
> >
> > diff --git a/man2/madvise.2 b/man2/madvise.2
> > index c1df67c..4704304 100644
> > --- a/man2/madvise.2
> > +++ b/man2/madvise.2
> > @@ -143,6 +143,25 @@ flag are special memory areas that are not managed
> > by the virtual memory subsystem.
> > Such pages are typically created by device drivers that
> > map the pages into user space.)
> > +.TP
> > +.B MADV_FREE " (since Linux 4.5)"
> > +Application is finished with the given range, so kernel can free
> > +resources associated with it but the freeing could be delayed until
> > +memory pressure happens or canceld by write operation by user.
> > +
> > +After a successful MADV_FREE operation, user shouldn't expect kernel
> > +keeps stale data on the page. However, subsequent write of pages
> > +in the range will succeed and then kernel cannot free those dirtied pages
> > +so user can always see just written data. If there was no subsequent
> > +write, kernel can free those clean pages any time. In such case,
> > +user can see zero-fill-on-demand pages.
> > +
> > +Note that, it works only with private anonymous pages (see
> > +.BR mmap (2)).
> > +On swapless system, freeing pages in given range happens instantly
> > +regardless of memory pressure.
> > +
> > +
> > .\"
> > .\" ======================================================================
> > .\"
> >
>
> Thanks for the nice text! I reworked somewhat, trying to fill out a
> few details about how I understand things work, but I may have introduced
> errors, so I would be happy if you would check the following text:
Below looks good to me.
Thanks, Michael
>
> MADV_FREE (since Linux 4.5)
> The application no longer requires the pages in the
> range specified by addr and len. The kernel can thus
> free these pages, but the freeing could be delayed until
> memory pressure occurs. For each of the pages that has
> been marked to be freed but has not yet been freed, the
> free operation will be canceled if the caller writes
> into the page. After a successful MADV_FREE operation,
> any stale data (i.e., dirty, unwritten pages) will be
> lost when the kernel frees the pages. However, subse‐
> quent writes to pages in the range will succeed and then
> kernel cannot free those dirtied pages, so that the
> caller can always see just written data. If there is no
> subsequent write, the kernel can free the pages at any
> time. Once pages in the range have been freed, the
> caller will see zero-fill-on-demand pages upon subse‐
> quent page references.
>
> The MADV_FREE operation can be applied only to private
> anonymous pages (see mmap(2)). On a swapless system,
> freeing pages in a given range happens instantly,
> regardless of memory pressure.
>
> Thanks,
>
> Michael
>
> --
> Michael Kerrisk
> Linux man-pages maintainer; http://www.kernel.org/doc/man-pages/
> Linux/UNIX System Programming Training: http://man7.org/training/
>
> --
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^ permalink raw reply [flat|nested] 6+ messages in thread
end of thread, other threads:[~2016-02-07 12:31 UTC | newest]
Thread overview: 6+ messages (download: mbox.gz / follow: Atom feed)
-- links below jump to the message on this page --
2016-02-05 2:15 [PATCH v5 00/12] MADV_FREE support Minchan Kim
2016-02-06 13:32 ` Michael Kerrisk (man-pages)
2016-02-07 12:31 ` Minchan Kim
-- strict thread matches above, loose matches on Subject: below --
2015-11-30 6:39 Minchan Kim
2016-01-28 7:16 ` Michael Kerrisk (man-pages)
2016-01-29 7:32 ` Minchan Kim
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