On Wed, Jul 15, 2015 at 6:54 AM, Vladimir Davydov
<vdavydov@xxxxxxxxxxxxx> wrote:
> /proc/kpagecgroup contains a 64-bit inode number of the memory cgroup
> each page is charged to, indexed by PFN. Having this information is
> useful for estimating a cgroup working set size.
>
> The file is present if CONFIG_PROC_PAGE_MONITOR && CONFIG_MEMCG.
>
> Signed-off-by: Vladimir Davydov <vdavydov@xxxxxxxxxxxxx>
> ---
> Documentation/vm/pagemap.txt | 6 ++++-
> fs/proc/page.c | 53 ++++++++++++++++++++++++++++++++++++++++++++
> 2 files changed, 58 insertions(+), 1 deletion(-)
>
> diff --git a/Documentation/vm/pagemap.txt b/Documentation/vm/pagemap.txt
> index 6bfbc172cdb9..a9b7afc8fbc6 100644
> --- a/Documentation/vm/pagemap.txt
> +++ b/Documentation/vm/pagemap.txt
> @@ -5,7 +5,7 @@ pagemap is a new (as of 2.6.25) set of interfaces in the kernel that allow
> userspace programs to examine the page tables and related information by
> reading files in /proc.
>
> -There are three components to pagemap:
> +There are four components to pagemap:
>
> * /proc/pid/pagemap. This file lets a userspace process find out which
> physical frame each virtual page is mapped to. It contains one 64-bit
> @@ -65,6 +65,10 @@ There are three components to pagemap:
> 23. BALLOON
> 24. ZERO_PAGE
>
> + * /proc/kpagecgroup. This file contains a 64-bit inode number of the
> + memory cgroup each page is charged to, indexed by PFN. Only available when
> + CONFIG_MEMCG is set.
> +
> Short descriptions to the page flags:
>
> 0. LOCKED
> diff --git a/fs/proc/page.c b/fs/proc/page.c
> index 7eee2d8b97d9..70d23245dd43 100644
> --- a/fs/proc/page.c
> +++ b/fs/proc/page.c
> @@ -9,6 +9,7 @@
> #include <linux/proc_fs.h>
> #include <linux/seq_file.h>
> #include <linux/hugetlb.h>
> +#include <linux/memcontrol.h>
> #include <linux/kernel-page-flags.h>
> #include <asm/uaccess.h>
> #include "internal.h"
> @@ -225,10 +226,62 @@ static const struct file_operations proc_kpageflags_operations = {
> .read = kpageflags_read,
> };
>
> +#ifdef CONFIG_MEMCG
> +static ssize_t kpagecgroup_read(struct file *file, char __user *buf,
> + size_t count, loff_t *ppos)
> +{
> + u64 __user *out = (u64 __user *)buf;
> + struct page *ppage;
> + unsigned long src = *ppos;
> + unsigned long pfn;
> + ssize_t ret = 0;
> + u64 ino;
> +
> + pfn = src / KPMSIZE;
> + count = min_t(unsigned long, count, (max_pfn * KPMSIZE) - src);
> + if (src & KPMMASK || count & KPMMASK)
> + return -EINVAL;
> +
> + while (count > 0) {
> + if (pfn_valid(pfn))
> + ppage = pfn_to_page(pfn);
> + else
> + ppage = NULL;
> +
> + if (ppage)
> + ino = page_cgroup_ino(ppage);
> + else
> + ino = 0;
> +
For both /proc/kpage* interfaces you add (and more critically for the
rmap-causing one, kpageidle):
It's a good idea to do cond_sched(). Whether after each pfn, each Nth
pfn, each put_user, I leave to you, but a reasonable cadence is
needed, because user-space can call this on the entire physical
address space, and that's a lot of work to do without re-scheduling.
Andres
> + if (put_user(ino, out)) {
> + ret = -EFAULT;
> + break;
> + }
> +
> + pfn++;
> + out++;
> + count -= KPMSIZE;
> + }
> +
> + *ppos += (char __user *)out - buf;
> + if (!ret)
> + ret = (char __user *)out - buf;
> + return ret;
> +}
> +
> +static const struct file_operations proc_kpagecgroup_operations = {
> + .llseek = mem_lseek,
> + .read = kpagecgroup_read,
> +};
> +#endif /* CONFIG_MEMCG */
> +
> static int __init proc_page_init(void)
> {
> proc_create("kpagecount", S_IRUSR, NULL, &proc_kpagecount_operations);
> proc_create("kpageflags", S_IRUSR, NULL, &proc_kpageflags_operations);
> +#ifdef CONFIG_MEMCG
> + proc_create("kpagecgroup", S_IRUSR, NULL, &proc_kpagecgroup_operations);
> +#endif
> return 0;
> }
> fs_initcall(proc_page_init);
> --
> 2.1.4
>
--
Andres Lagar-Cavilla | Google Kernel Team | andreslc@xxxxxxxxxx
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