Re: [PATCH V2] Doc: admin-guide: Add entry for kvm_cma_resv_ratio kernel param
From: Paul Mackerras <hidden>
Date: 2020-09-21 23:19:34
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linux-doc, lkml
On Mon, Sep 21, 2020 at 02:32:20PM +0530, sathnaga@linux.vnet.ibm.com wrote:
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From: Satheesh Rajendran <redacted> Add document entry for kvm_cma_resv_ratio kernel param which is used to alter the KVM contiguous memory allocation percentage for hash pagetable allocation used by hash mode PowerPC KVM guests. Cc: linux-kernel@vger.kernel.org Cc: kvm-ppc@vger.kernel.org Cc: linuxppc-dev@lists.ozlabs.org Cc: Paul Mackerras <redacted> Cc: Michael Ellerman <mpe@ellerman.id.au> Cc: Jonathan Corbet <corbet@lwn.net> Reviewed-by: Randy Dunlap <redacted> Signed-off-by: Satheesh Rajendran <redacted> --- V2: Addressed review comments from Randy. V1: https://lkml.org/lkml/2020/9/16/72 --- Documentation/admin-guide/kernel-parameters.txt | 8 ++++++++ 1 file changed, 8 insertions(+)diff --git a/Documentation/admin-guide/kernel-parameters.txt b/Documentation/admin-guide/kernel-parameters.txt index a1068742a6df..932ed45740c9 100644 --- a/Documentation/admin-guide/kernel-parameters.txt +++ b/Documentation/admin-guide/kernel-parameters.txt@@ -2258,6 +2258,14 @@ [KVM,ARM] Allow use of GICv4 for direct injection of LPIs. + kvm_cma_resv_ratio=n [PPC] + Reserves given percentage from system memory area for + contiguous memory allocation for KVM hash pagetable + allocation. + By default it reserves 5% of total system memory.
I am concerned that using the term "reserve" here could give the impression that this memory is then not available for any other use. It is in fact available for other uses as long as they are movable allocations. So this memory is available for uses such as process anonymous memory and page cache, just not for things like kmalloc. I'm not sure what would be a better term than "reserve", though. Perhaps we need to add a sentence something like "The reserved memory is available for use as process memory and page cache when it is not being used by KVM." Paul.