2021-07-27 05:37:42

by Vasily Averin

Subject: [PATCH v7 10/10] memcg: enable accounting for ldt_struct objects

Each task can request own LDT and force the kernel to allocate up to
64Kb memory per-mm.

There are legitimate workloads with hundreds of processes and there
can be hundreds of workloads running on large machines.
The unaccounted memory can cause isolation issues between the workloads
particularly on highly utilized machines.

It makes sense to account for this objects to restrict the host's memory
consumption from inside the memcg-limited container.

Signed-off-by: Vasily Averin <[email protected]>
Acked-by: Borislav Petkov <[email protected]>
---
arch/x86/kernel/ldt.c | 6 +++---
1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/arch/x86/kernel/ldt.c b/arch/x86/kernel/ldt.c
index aa15132..525876e 100644
--- a/arch/x86/kernel/ldt.c
+++ b/arch/x86/kernel/ldt.c
@@ -154,7 +154,7 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries)
if (num_entries > LDT_ENTRIES)
return NULL;

- new_ldt = kmalloc(sizeof(struct ldt_struct), GFP_KERNEL);
+ new_ldt = kmalloc(sizeof(struct ldt_struct), GFP_KERNEL_ACCOUNT);
if (!new_ldt)
return NULL;

@@ -168,9 +168,9 @@ static struct ldt_struct *alloc_ldt_struct(unsigned int num_entries)
* than PAGE_SIZE.
*/
if (alloc_size > PAGE_SIZE)
- new_ldt->entries = vzalloc(alloc_size);
+ new_ldt->entries = __vmalloc(alloc_size, GFP_KERNEL_ACCOUNT | __GFP_ZERO);
else
- new_ldt->entries = (void *)get_zeroed_page(GFP_KERNEL);
+ new_ldt->entries = (void *)get_zeroed_page(GFP_KERNEL_ACCOUNT);

if (!new_ldt->entries) {
kfree(new_ldt);
--
1.8.3.1

2021-07-27 22:38:07

by Shakeel Butt

Subject: Re: [PATCH v7 10/10] memcg: enable accounting for ldt_struct objects

On Mon, Jul 26, 2021 at 10:34 PM Vasily Averin <[email protected]> wrote:
>
> Each task can request own LDT and force the kernel to allocate up to
> 64Kb memory per-mm.
>
> There are legitimate workloads with hundreds of processes and there
> can be hundreds of workloads running on large machines.
> The unaccounted memory can cause isolation issues between the workloads
> particularly on highly utilized machines.
>
> It makes sense to account for this objects to restrict the host's memory
> consumption from inside the memcg-limited container.
>
> Signed-off-by: Vasily Averin <[email protected]>
> Acked-by: Borislav Petkov <[email protected]>

Reviewed-by: Shakeel Butt <[email protected]>