As per the documentation, Kernel Samepage Merging (available
since 2.6.32) is a memory-saving de-duplication feature,
enabled by CONFIG_KSM=y and activated via sysfs. More
information can be found here:
https://www.kernel.org/doc/Documentation/vm/ksm.txt
When enabled in the kernel, the default is to not do anything
at all, until it is activated at run-time with:
echo 1 > /sys/kernel/mm/ksm/run
Signed-off-by: Daniel Díaz <[email protected]>
---
arch/x86/configs/x86_64_defconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/x86/configs/x86_64_defconfig b/arch/x86/configs/x86_64_defconfig
index e32fc1f..8fd7396 100644
--- a/arch/x86/configs/x86_64_defconfig
+++ b/arch/x86/configs/x86_64_defconfig
@@ -48,6 +48,7 @@ CONFIG_MICROCODE_AMD=y
CONFIG_X86_MSR=y
CONFIG_X86_CPUID=y
CONFIG_NUMA=y
+CONFIG_KSM=y
CONFIG_X86_CHECK_BIOS_CORRUPTION=y
# CONFIG_MTRR_SANITIZER is not set
CONFIG_EFI=y
--
2.7.4
As per the documentation, Kernel Samepage Merging (available
since 2.6.32) is a memory-saving de-duplication feature,
enabled by CONFIG_KSM=y and activated via sysfs. More
information can be found here:
https://www.kernel.org/doc/Documentation/vm/ksm.txt
When enabled in the kernel, the default is to not do anything
at all, until it is activated at run-time with:
echo 1 > /sys/kernel/mm/ksm/run
Signed-off-by: Daniel Díaz <[email protected]>
---
arch/arm/configs/multi_v7_defconfig | 1 +
1 file changed, 1 insertion(+)
diff --git a/arch/arm/configs/multi_v7_defconfig b/arch/arm/configs/multi_v7_defconfig
index 7e1c543..79eedf4d 100644
--- a/arch/arm/configs/multi_v7_defconfig
+++ b/arch/arm/configs/multi_v7_defconfig
@@ -133,6 +133,7 @@ CONFIG_SMP=y
CONFIG_NR_CPUS=16
CONFIG_HIGHPTE=y
CONFIG_CMA=y
+CONFIG_KSM=y
CONFIG_SECCOMP=y
CONFIG_ARM_APPENDED_DTB=y
CONFIG_ARM_ATAG_DTB_COMPAT=y
--
2.7.4
Hi Daniel,
Thanks for your patch!
On Fri, Jun 15, 2018 at 12:52 AM Daniel Díaz <[email protected]> wrote:
> As per the documentation, Kernel Samepage Merging (available
> since 2.6.32) is a memory-saving de-duplication feature,
> enabled by CONFIG_KSM=y and activated via sysfs. More
> information can be found here:
> https://www.kernel.org/doc/Documentation/vm/ksm.txt
>
> When enabled in the kernel, the default is to not do anything
> at all, until it is activated at run-time with:
> echo 1 > /sys/kernel/mm/ksm/run
So that's the "what" part.
Why is it good to have this in multi_v7_defconfig, which is meant to ease
(compile)testing for as many supported ARM v7 SoCs as possible?
Thanks!
Gr{oetje,eeting}s,
Geert
--
Geert Uytterhoeven -- There's lots of Linux beyond ia32 -- [email protected]
In personal conversations with technical people, I call myself a hacker. But
when I'm talking to journalists I just say "programmer" or something like that.
-- Linus Torvalds
On Thu, 14 Jun 2018, Daniel Díaz wrote:
> As per the documentation, Kernel Samepage Merging (available
> since 2.6.32) is a memory-saving de-duplication feature,
> enabled by CONFIG_KSM=y and activated via sysfs. More
> information can be found here:
> https://www.kernel.org/doc/Documentation/vm/ksm.txt
>
> When enabled in the kernel, the default is to not do anything
> at all, until it is activated at run-time with:
> echo 1 > /sys/kernel/mm/ksm/run
We all know that, but the above does not make an argument WHY this needs to
be enabled in defconfig.
Thanks,
tglx
On 2018-06-14 18:50, Daniel Díaz wrote:
> As per the documentation, Kernel Samepage Merging (available
> since 2.6.32) is a memory-saving de-duplication feature,
> enabled by CONFIG_KSM=y and activated via sysfs. More
> information can be found here:
> https://www.kernel.org/doc/Documentation/vm/ksm.txt
>
> When enabled in the kernel, the default is to not do anything
> at all, until it is activated at run-time with:
> echo 1 > /sys/kernel/mm/ksm/run
>
As pointed out by a couple of others, this doesn't explain why this is a
good idea. All you're doing here is giving a reason that it won't have
a negative impact on most users.
Two points that may be worth adding, but also don't really argue for it
being a significant improvement:
* Pretty much all of the major distributions that use pre-built kernels
have it enabled in their kernels (At minimum, Debian, Ubuntu, Fedora
(and by extension RHEL and CentOS), openSUSE (and by extension SLES),
Arch, and Alpine have it enabled), so enabling this in defconfig would
bring it a bit closer to parity with distribution kernels in terms of
core features.
* Software other than QEMU is starting to take advantage of it if
available (for example, Netdata [1] can mark it's in-memory TSDB's for
deduplication, which usually cuts it's memory usage roughly in half).
[1] https://my-netdata.io/