COMPACTION and TRANSPARENT_HUGEPAGE config warning
Subsystems (2)
Hello Andrea,
this commit:
commit 5d6892407cab23d4bf2f6de065ca351a53849323
Author: Andrea Arcangeli <[email protected]> Date: Thu Jan 13 15:47:07 2011 -0800
thp: select CONFIG_COMPACTION if TRANSPARENT_HUGEPAGE enabled
causes this warning during the configuration process:
warning: (TRANSPARENT_HUGEPAGE) selects COMPACTION which has unmet direct dependencies (EXPERIMENTAL && HUGETLB_PAGE && MMU)
This happens because 'select' does not enable the dependencies of its target, so when I selected THP it also enabled COMPATION but I don't have HUGETLBFS (=HUGETLB_PAGE) enabled.
Making THP select HUGETLB_PAGE fixes the warning but I'm not 100% sure that's correct (does it work without HUGETLBFS?).
Luca
PATCH 1/1 compaction: don't depend on HUGETLB_PAGE
Hello,
Quoted 11 lines · Luca Tettamanti
Hello Andrea,
this commit:commit
5d6892407cab23d4bf2f6de065ca351a53849323Author: Andrea Arcangeli <[email protected]> Date: Thu Jan 13 15:47:07 2011 -0800thp: select
CONFIG_COMPACTIONifTRANSPARENT_HUGEPAGEenabledcauses this warning during the configuration process:
Quoted 8 lines
warning: (
TRANSPARENT_HUGEPAGE) selects COMPACTION which has unmet direct dependencies (EXPERIMENTAL &&HUGETLB_PAGE&& MMU)This happens because 'select' does not enable the dependencies of its target, so when I selected THP it also enabled COMPATION but I don't have HUGETLBFS (=HUGETLB_PAGE) enabled.
Making THP selectHUGETLB_PAGEfixes the warning but I'm not 100% sure that's correct (does it work without HUGETLBFS?).
Mel, what's your take about this issue?
Luca does the below fix all your .config problems?
====
Subject: compaction: don't depend on HUGETLB_PAGE
From: Andrea Arcangeli <[email protected]>
COMPACTION doesn't depend on HUGETLB_PAGE, it doesn't depend on THP either, it is also useful for regular alloc_pages(order > 0) including the very kernel stack during fork (THREAD_ORDER = 1). It's always better to enable COMPACTION.
The warning should be an error because we would end up with MIGRATION not selected, and COMPACTION wouldn't work without migration (despite it seems to build with an inline migrate_pages returning -ENOSYS).
I'd also like to remove EXPERIMENTAL: compaction has been in the kernel for some releases (for full safety the default remains disabled which I think is enough).
---
mm/Kconfig +1 -1
@@ -179,7 +179,7 @@ config SPLIT_PTLOCK_CPUS config COMPACTION bool "Allow for memory compaction" select MIGRATION - depends on EXPERIMENTAL && HUGETLB_PAGE && MMU + depends on MMU help Allows the compaction of memory for the allocation of huge pages.
Re: [PATCH] compaction: don't depend on HUGETLB_PAGE
Quoted 23 lines · Andrea Arcangeli
Hello,
Quoted 11 lines · Luca Tettamanti
Hello Andrea,
this commit:commit
5d6892407cab23d4bf2f6de065ca351a53849323
Author: Andrea Arcangeli <[email protected]>
Date: Thu Jan 13 15:47:07 2011 -0800thp: select
CONFIG_COMPACTIONifTRANSPARENT_HUGEPAGEenabledcauses this warning during the configuration process:
Quoted 8 lines
warning: (
TRANSPARENT_HUGEPAGE) selects COMPACTION which has unmet direct dependencies (EXPERIMENTAL &&HUGETLB_PAGE&& MMU)This happens because 'select' does not enable the dependencies of its target, so when I selected THP it also enabled COMPATION but I don't have HUGETLBFS (=HUGETLB_PAGE) enabled.
Making THP selectHUGETLB_PAGEfixes the warning but I'm not 100% sure that's correct (does it work without HUGETLBFS?).
Quoted 3 lines
Mel, what's your take about this issue?
Luca does the below fix all your .config problems?
Yes, no more warnings; I haven't tested the kernel though.
Luca
Quoted 12 lines
mm/Kconfig +0
-0@@ -179,7 +179,7 @@ config SPLIT_PTLOCK_CPUSconfig COMPACTION
bool "Allow for memory compaction"
select MIGRATION
- depends on EXPERIMENTAL &&HUGETLB_PAGE&& MMU
+ depends on MMU
help
Allows the compaction of memory for the allocation of huge pages.
Re: [PATCH] compaction: don't depend on HUGETLB_PAGE
In reply to Andrea ArcangeliQuoted 17 lines · Andrea Arcangeli
Hello,
Quoted 14 lines · Luca Tettamanti
Hello Andrea,
this commit:commit
5d6892407cab23d4bf2f6de065ca351a53849323Author: Andrea Arcangeli <[email protected]> Date: Thu Jan 13 15:47:07 2011 -0800thp: select
CONFIG_COMPACTIONifTRANSPARENT_HUGEPAGEenabledcauses this warning during the configuration process:
warning: (
TRANSPARENT_HUGEPAGE) selects COMPACTION which has unmet direct dependencies (EXPERIMENTAL &&HUGETLB_PAGE&& MMU)
Quoted 8 lines
Quoted 5 lines
This happens because 'select' does not enable the dependencies of its target, so when I selected THP it also enabled COMPATION but I don't have HUGETLBFS (=HUGETLB_PAGE) enabled.
Making THP selectHUGETLB_PAGEfixes the warning but I'm not 100% sure that's correct (does it work without HUGETLBFS?).Mel, what's your take about this issue?
The dependencies were only in the name of being conservative. Hugetlbfs was initially the only expected user of compaction so making it depend was meant to restrict who might enable it and is not a true dependency. It was marked experimental at the start for obvious reasons.
Quoted 16 lines
Luca does the below fix all your .config problems?
====
Subject: compaction: don't depend onHUGETLB_PAGEFrom: Andrea Arcangeli <[email protected]>
COMPACTION doesn't depend on
HUGETLB_PAGE, it doesn't depend on THP either, it is also useful for regularalloc_pages(order > 0)including the very kernel stack during fork (THREAD_ORDER= 1). It's always better to enable COMPACTION.The warning should be an error because we would end up with MIGRATION not selected, and COMPACTION wouldn't work without migration (despite it seems to build with an inline
migrate_pagesreturning-ENOSYS).
Quoted 5 lines
I'd also like to remove EXPERIMENTAL: compaction has been in the kernel for some releases (for full safety the default remains disabled which I think is enough).
Signed-off-by Andrea Arcangeli <[email protected]>
I think this is reasonable;
Quoted 16 lines
---
mm/Kconfig +1
-1@@ -179,7 +179,7 @@ config SPLIT_PTLOCK_CPUS config COMPACTION bool "Allow for memory compaction" select MIGRATION - depends on EXPERIMENTAL && HUGETLB_PAGE && MMU + depends on MMU help Allows the compaction of memory for the allocation of huge pages.
Signature · 3 lines
Mel Gorman Linux Technology Center IBM Dublin Software Lab