Re: [PATCH v8 6/9] secretmem: add memcg accounting

Roman Gushchin
2020-11-13T23:42:39Z

вт, 10 нояб. 2020 г. в 07:16, Mike Rapoport <rppt@kernel.org>:
>
> From: Mike Rapoport <rppt@linux.ibm.com>
>
> Account memory consumed by secretmem to memcg. The accounting is updated
> when the memory is actually allocated and freed.
>
> Signed-off-by: Mike Rapoport <rppt@linux.ibm.com>
> ---
> mm/filemap.c | 2 +-
> mm/secretmem.c | 42 +++++++++++++++++++++++++++++++++++++++++-
> 2 files changed, 42 insertions(+), 2 deletions(-)
>
> diff --git a/mm/filemap.c b/mm/filemap.c
> index 249cf489f5df..11387a077373 100644
> --- a/mm/filemap.c
> +++ b/mm/filemap.c
> @@ -844,7 +844,7 @@ static noinline int __add_to_page_cache_locked(struct page *page,
> page->mapping = mapping;
> page->index = offset;
>
> - if (!huge) {
> + if (!huge && !page->memcg_data) {
> error = mem_cgroup_charge(page, current->mm, gfp);
> if (error)
> goto error;
> diff --git a/mm/secretmem.c b/mm/secretmem.c
> index 1aa2b7cffe0d..1eb7667016fa 100644
> --- a/mm/secretmem.c
> +++ b/mm/secretmem.c
> @@ -17,6 +17,7 @@
> #include <linux/syscalls.h>
> #include <linux/memblock.h>
> #include <linux/pseudo_fs.h>
> +#include <linux/memcontrol.h>
> #include <linux/set_memory.h>
> #include <linux/sched/signal.h>
>
> @@ -49,6 +50,38 @@ struct secretmem_ctx {
>
> static struct cma *secretmem_cma;
>

Hi Mike!

> +static int secretmem_memcg_charge(struct page *page, gfp_t gfp, int order)
> +{
> + unsigned long nr_pages = (1 << order);
> + int i, err;
> +
> + err = memcg_kmem_charge_page(page, gfp, order);
> + if (err)
> + return err;
> +
> + for (i = 1; i < nr_pages; i++) {
> + struct page *p = page + i;
> +
> + p->memcg_data = page->memcg_data;
> + }

Hm, it looks very strange to me. Why do we need to copy memcg_data?
What about css reference counting?

And what about statistics?

I'm sorry for being late.

Thank you!

> +
> + return 0;
> +}
> +
> +static void secretmem_memcg_uncharge(struct page *page, int order)
> +{
> + unsigned long nr_pages = (1 << order);
> + int i;
> +
> + for (i = 1; i < nr_pages; i++) {
> + struct page *p = page + i;
> +
> + p->memcg_data = 0;
> + }
> +
> + memcg_kmem_uncharge_page(page, PMD_PAGE_ORDER);
> +}
> +
> static int secretmem_pool_increase(struct secretmem_ctx *ctx, gfp_t gfp)
> {
> unsigned long nr_pages = (1 << PMD_PAGE_ORDER);
> @@ -61,10 +94,14 @@ static int secretmem_pool_increase(struct secretmem_ctx *ctx, gfp_t gfp)
> if (!page)
> return -ENOMEM;
>
> - err = set_direct_map_invalid_noflush(page, nr_pages);
> + err = secretmem_memcg_charge(page, gfp, PMD_PAGE_ORDER);
> if (err)
> goto err_cma_release;
>
> + err = set_direct_map_invalid_noflush(page, nr_pages);
> + if (err)
> + goto err_memcg_uncharge;
> +
> addr = (unsigned long)page_address(page);
> err = gen_pool_add(pool, addr, PMD_SIZE, NUMA_NO_NODE);
> if (err)
> @@ -81,6 +118,8 @@ static int secretmem_pool_increase(struct secretmem_ctx *ctx, gfp_t gfp)
> * won't fail
> */
> set_direct_map_default_noflush(page, nr_pages);
> +err_memcg_uncharge:
> + secretmem_memcg_uncharge(page, PMD_PAGE_ORDER);
> err_cma_release:
> cma_release(secretmem_cma, page, nr_pages);
> return err;
> @@ -310,6 +349,7 @@ static void secretmem_cleanup_chunk(struct gen_pool *pool,
> int i;
>
> set_direct_map_default_noflush(page, nr_pages);
> + secretmem_memcg_uncharge(page, PMD_PAGE_ORDER);
>
> for (i = 0; i < nr_pages; i++)
> clear_highpage(page + i);
> --
> 2.28.0
>
>