Until we have better performance numbers on the lazy reclaim path,
we can just alias MADV_FREE to MADV_DONTNEED with this trivial
patch.
This way glibc can go ahead with the optimization on their side
and we can figure out the kernel side later.
Signed-off-by: Rik van Riel <[email protected]>
---
When I get back from the Red Hat Summit (Saturday), I will run more
performance numbers with and without the lazy reclaiming of pages.
Nick Piggin wrote:
Ulrich Drepper wrote:
Nick Piggin wrote:
What I found is that, on this system, MADV_FREE performance improvement
was in the noise when you look at it on top of the MADV_DONTNEED glibc
and down_read(mmap_sem) patch in sysbench.
I don't want to judge the numbers since I cannot but I want to make an
observations: even if in the SMP case MADV_FREE turns out to not be a
bigger boost then there is still the UP case to keep in mind where Rik
measured a significant speed-up. As long as the SMP case isn't hurt
this is reaosn enough to use the patch. With more and more cores on one
processor SMP systems are pushed evermore to the high-end side. You'll
find many installations which today use SMP will be happy enough with
many-core UP machines.
OK, sure. I think we need more numbers though.
And even if this was a patch with _no_ possibility for regressions and it
was a completely trivial one that improves performance in some cases...
one big problem is that it uses another page flag.
I literally have about 4 or 5 new page flags I'd like to add today :) I
can't of course, because we have very few spare ones left.
From the MySQL numbers on this system, it seems like performance is in the
noise, and MADV_DONTNEED makes the _vast_ majority of the improvement.
This is also the case with Rik's benchmarks, and while he did see some
improvement, I found the runs to be quite variable, so it would be ideal
to get a larger sample.
And the fact that the poor behaviour of the old style malloc/free went
unnoticed for so long indicates that it won't be the end of the world if
we didn't merge MADV_FREE right now.
--
Politics is the struggle between those who want to make their country
the best in the world, and those who believe it already is. Each group
calls the other unpatriotic.
include/asm-alpha/mman.h | 1 +
include/asm-generic/mman.h | 1 +
include/asm-mips/mman.h | 1 +
include/asm-parisc/mman.h | 1 +
include/asm-sparc/mman.h | 2 --
include/asm-sparc64/mman.h | 2 --
include/asm-xtensa/mman.h | 1 +
mm/madvise.c | 2 ++
8 files changed, 7 insertions(+), 4 deletions(-)
diff --git a/include/asm-alpha/mman.h b/include/asm-alpha/mman.h
index 90d7c35..d47b5a3 100644
--- a/include/asm-alpha/mman.h
+++ b/include/asm-alpha/mman.h
@@ -42,6 +42,7 @@ #define MADV_SEQUENTIAL 2 /* expect seq
#define MADV_WILLNEED 3 /* will need these pages */
#define MADV_SPACEAVAIL 5 /* ensure resources are available */
#define MADV_DONTNEED 6 /* don't need these pages */
+#define MADV_FREE 7 /* don't need the pages or the data */
/* common/generic parameters */
#define MADV_REMOVE 9 /* remove these pages & resources */
diff --git a/include/asm-generic/mman.h b/include/asm-generic/mman.h
index 5e3dde2..34a9ff1 100644
--- a/include/asm-generic/mman.h
+++ b/include/asm-generic/mman.h
@@ -29,6 +29,7 @@ #define MADV_RANDOM 1 /* expect random
#define MADV_SEQUENTIAL 2 /* expect sequential page references */
#define MADV_WILLNEED 3 /* will need these pages */
#define MADV_DONTNEED 4 /* don't need these pages */
+#define MADV_FREE 5 /* don't need the pages or the data */
/* common parameters: try to keep these consistent across architectures */
#define MADV_REMOVE 9 /* remove these pages & resources */
diff --git a/include/asm-mips/mman.h b/include/asm-mips/mman.h
index e4d6f1f..68067ff 100644
--- a/include/asm-mips/mman.h
+++ b/include/asm-mips/mman.h
@@ -65,6 +65,7 @@ #define MADV_RANDOM 1 /* expect random
#define MADV_SEQUENTIAL 2 /* expect sequential page references */
#define MADV_WILLNEED 3 /* will need these pages */
#define MADV_DONTNEED 4 /* don't need these pages */
+#define MADV_FREE 5 /* don't need the pages or the data */
/* common parameters: try to keep these consistent across architectures */
#define MADV_REMOVE 9 /* remove these pages & resources */
diff --git a/include/asm-parisc/mman.h b/include/asm-parisc/mman.h
index defe752..347fbca 100644
--- a/include/asm-parisc/mman.h
+++ b/include/asm-parisc/mman.h
@@ -38,6 +38,7 @@ #define MADV_DONTNEED 4
#define MADV_SPACEAVAIL 5 /* insure that resources are reserved */
#define MADV_VPS_PURGE 6 /* Purge pages from VM page cache */
#define MADV_VPS_INHERIT 7 /* Inherit parents page size */
+#define MADV_FREE 8 /* don't need the pages or the data */
/* common/generic parameters */
#define MADV_REMOVE 9 /* remove these pages & resources */
diff --git a/include/asm-sparc/mman.h b/include/asm-sparc/mman.h
index b7dc40b..5ec7106 100644
--- a/include/asm-sparc/mman.h
+++ b/include/asm-sparc/mman.h
@@ -33,8 +33,6 @@ #define MC_UNLOCK 3 /* Unlock pag
#define MC_LOCKAS 5 /* Lock an entire address space of the calling process */
#define MC_UNLOCKAS 6 /* Unlock entire address space of calling process */
-#define MADV_FREE 0x5 /* (Solaris) contents can be freed */
-
#ifdef __KERNEL__
#ifndef __ASSEMBLY__
#define arch_mmap_check sparc_mmap_check
diff --git a/include/asm-sparc64/mman.h b/include/asm-sparc64/mman.h
index 8cc1860..03b05d5 100644
--- a/include/asm-sparc64/mman.h
+++ b/include/asm-sparc64/mman.h
@@ -33,8 +33,6 @@ #define MC_UNLOCK 3 /* Unlock pag
#define MC_LOCKAS 5 /* Lock an entire address space of the calling process */
#define MC_UNLOCKAS 6 /* Unlock entire address space of calling process */
-#define MADV_FREE 0x5 /* (Solaris) contents can be freed */
-
#ifdef __KERNEL__
#ifndef __ASSEMBLY__
#define arch_mmap_check sparc64_mmap_check
diff --git a/include/asm-xtensa/mman.h b/include/asm-xtensa/mman.h
index 9b92620..1345703 100644
--- a/include/asm-xtensa/mman.h
+++ b/include/asm-xtensa/mman.h
@@ -72,6 +72,7 @@ #define MADV_RANDOM 1 /* expect random
#define MADV_SEQUENTIAL 2 /* expect sequential page references */
#define MADV_WILLNEED 3 /* will need these pages */
#define MADV_DONTNEED 4 /* don't need these pages */
+#define MADV_FREE 5 /* don't need the pages or the data */
/* common parameters: try to keep these consistent across architectures */
#define MADV_REMOVE 9 /* remove these pages & resources */
diff --git a/mm/madvise.c b/mm/madvise.c
index e75096b..ad067f2 100644
--- a/mm/madvise.c
+++ b/mm/madvise.c
@@ -22,6 +22,7 @@ static int madvise_need_mmap_write(int b
case MADV_REMOVE:
case MADV_WILLNEED:
case MADV_DONTNEED:
+ case MADV_FREE:
return 0;
default:
/* be safe, default to 1. list exceptions explicitly */
@@ -234,6 +235,7 @@ madvise_vma(struct vm_area_struct *vma,
break;
case MADV_DONTNEED:
+ case MADV_FREE:
error = madvise_dontneed(vma, prev, start, end);
break;
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