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

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Date:   Fri, 13 Nov 2020 15:42:25 -0800
From:   Roman Gushchin <guroan@...il.com>
To:     Mike Rapoport <rppt@...nel.org>
Cc:     Andrew Morton <akpm@...ux-foundation.org>,
        Alexander Viro <viro@...iv.linux.org.uk>,
        Andy Lutomirski <luto@...nel.org>,
        Arnd Bergmann <arnd@...db.de>, Borislav Petkov <bp@...en8.de>,
        Catalin Marinas <catalin.marinas@....com>,
        Christopher Lameter <cl@...ux.com>,
        Dan Williams <dan.j.williams@...el.com>,
        Dave Hansen <dave.hansen@...ux.intel.com>,
        David Hildenbrand <david@...hat.com>,
        Elena Reshetova <elena.reshetova@...el.com>,
        "H. Peter Anvin" <hpa@...or.com>, Ingo Molnar <mingo@...hat.com>,
        James Bottomley <jejb@...ux.ibm.com>,
        "Kirill A. Shutemov" <kirill@...temov.name>,
        Matthew Wilcox <willy@...radead.org>,
        Mark Rutland <mark.rutland@....com>,
        Mike Rapoport <rppt@...ux.ibm.com>,
        Michael Kerrisk <mtk.manpages@...il.com>,
        Palmer Dabbelt <palmer@...belt.com>,
        Paul Walmsley <paul.walmsley@...ive.com>,
        Peter Zijlstra <peterz@...radead.org>,
        Rick Edgecombe <rick.p.edgecombe@...el.com>,
        Shuah Khan <shuah@...nel.org>,
        Thomas Gleixner <tglx@...utronix.de>,
        Tycho Andersen <tycho@...ho.ws>, Will Deacon <will@...nel.org>,
        linux-api@...r.kernel.org, linux-arch@...r.kernel.org,
        linux-arm-kernel@...ts.infradead.org,
        linux-fsdevel@...r.kernel.org, linux-mm@...ck.org,
        linux-kernel@...r.kernel.org, linux-kselftest@...r.kernel.org,
        linux-nvdimm@...ts.01.org, linux-riscv@...ts.infradead.org,
        x86@...nel.org
Subject: Re: [PATCH v8 6/9] secretmem: add memcg accounting

вт, 10 нояб. 2020 г. в 07:16, Mike Rapoport <rppt@...nel.org>:
>
> From: Mike Rapoport <rppt@...ux.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@...ux.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
>
>