Re: [PATCH v16 02/14] mm: Introduce Data Access MONitor (DAMON)

[<vrd@amazon.com>]

On 6/15/20 6:19 PM, SeongJae Park wrote:
> From: SeongJae Park <sjpark@amazon.de>
> 
> This commit introduces a kernel module named DAMON.  Note that this
> commit is implementing only the stub for the module load/unload, basic
> data structures, and simple manipulation functions of the structures to
> keep the size of commit small.  The core mechanisms of DAMON will be
> implemented one by one by following commits.
> 
> Signed-off-by: SeongJae Park <sjpark@amazon.de>
> Reviewed-by: Leonard Foerster <foersleo@amazon.de>
> ---

Reviewed-by: Varad Gautam <vrd@amazon.de>

>  include/linux/damon.h |  63 ++++++++++++++
>  mm/Kconfig            |  12 +++
>  mm/Makefile           |   1 +
>  mm/damon.c            | 188 ++++++++++++++++++++++++++++++++++++++++++
>  4 files changed, 264 insertions(+)
>  create mode 100644 include/linux/damon.h
>  create mode 100644 mm/damon.c
> 
> diff --git a/include/linux/damon.h b/include/linux/damon.h
> new file mode 100644
> index 000000000000..c8f8c1c41a45
> --- /dev/null
> +++ b/include/linux/damon.h
> @@ -0,0 +1,63 @@
> +/* SPDX-License-Identifier: GPL-2.0 */
> +/*
> + * DAMON api
> + *
> + * Copyright 2019-2020 Amazon.com, Inc. or its affiliates.
> + *
> + * Author: SeongJae Park <sjpark@amazon.de>
> + */
> +
> +#ifndef _DAMON_H_
> +#define _DAMON_H_
> +
> +#include <linux/random.h>
> +#include <linux/types.h>
> +
> +/**
> + * struct damon_addr_range - Represents an address region of [@start, @end).
> + * @start:	Start address of the region (inclusive).
> + * @end:	End address of the region (exclusive).
> + */
> +struct damon_addr_range {
> +	unsigned long start;
> +	unsigned long end;
> +};
> +
> +/**
> + * struct damon_region - Represents a monitoring target region.
> + * @ar:			The address range of the region.
> + * @sampling_addr:	Address of the sample for the next access check.
> + * @nr_accesses:	Access frequency of this region.
> + * @list:		List head for siblings.
> + */
> +struct damon_region {
> +	struct damon_addr_range ar;
> +	unsigned long sampling_addr;
> +	unsigned int nr_accesses;
> +	struct list_head list;
> +};
> +
> +/**
> + * struct damon_task - Represents a monitoring target task.
> + * @pid:		Process id of the task.
> + * @regions_list:	Head of the monitoring target regions of this task.
> + * @list:		List head for siblings.
> + *
> + * If the monitoring target address space is task independent (e.g., physical
> + * memory address space monitoring), @pid should be '-1'.
> + */
> +struct damon_task {
> +	int pid;
> +	struct list_head regions_list;
> +	struct list_head list;
> +};
> +
> +/**
> + * struct damon_ctx - Represents a context for each monitoring.
> + * @tasks_list:		Head of monitoring target tasks (&damon_task) list.
> + */
> +struct damon_ctx {
> +	struct list_head tasks_list;	/* 'damon_task' objects */
> +};
> +
> +#endif
> diff --git a/mm/Kconfig b/mm/Kconfig
> index c1acc34c1c35..ecea0889ea35 100644
> --- a/mm/Kconfig
> +++ b/mm/Kconfig
> @@ -867,4 +867,16 @@ config ARCH_HAS_HUGEPD
>  config MAPPING_DIRTY_HELPERS
>          bool
>  
> +config DAMON
> +	tristate "Data Access Monitor"
> +	depends on MMU
> +	help
> +	  Provides data access monitoring.
> +
> +	  DAMON is a kernel module that allows users to monitor the actual
> +	  memory access pattern of specific user-space processes.  It aims to
> +	  be 1) accurate enough to be useful for performance-centric domains,
> +	  and 2) sufficiently light-weight so that it can be applied online.
> +	  If unsure, say N.
> +
>  endmenu
> diff --git a/mm/Makefile b/mm/Makefile
> index fccd3756b25f..230e545b6e07 100644
> --- a/mm/Makefile
> +++ b/mm/Makefile
> @@ -112,3 +112,4 @@ obj-$(CONFIG_MEMFD_CREATE) += memfd.o
>  obj-$(CONFIG_MAPPING_DIRTY_HELPERS) += mapping_dirty_helpers.o
>  obj-$(CONFIG_PTDUMP_CORE) += ptdump.o
>  obj-$(CONFIG_PAGE_REPORTING) += page_reporting.o
> +obj-$(CONFIG_DAMON) += damon.o
> diff --git a/mm/damon.c b/mm/damon.c
> new file mode 100644
> index 000000000000..2bf35bdc0470
> --- /dev/null
> +++ b/mm/damon.c
> @@ -0,0 +1,188 @@
> +// SPDX-License-Identifier: GPL-2.0
> +/*
> + * Data Access Monitor
> + *
> + * Copyright 2019-2020 Amazon.com, Inc. or its affiliates.
> + *
> + * Author: SeongJae Park <sjpark@amazon.de>
> + *
> + * This file is constructed in below parts.
> + *
> + * - Functions and macros for DAMON data structures
> + * - Functions for the module loading/unloading
> + *
> + * The core parts are not implemented yet.
> + */
> +
> +#define pr_fmt(fmt) "damon: " fmt
> +
> +#include <linux/damon.h>
> +#include <linux/mm.h>
> +#include <linux/module.h>
> +#include <linux/slab.h>
> +
> +/*
> + * Functions and macros for DAMON data structures
> + */
> +
> +#define damon_get_task_struct(t) \
> +	(get_pid_task(find_vpid(t->pid), PIDTYPE_PID))
> +
> +#define damon_next_region(r) \
> +	(container_of(r->list.next, struct damon_region, list))
> +
> +#define damon_prev_region(r) \
> +	(container_of(r->list.prev, struct damon_region, list))
> +
> +#define damon_for_each_region(r, t) \
> +	list_for_each_entry(r, &t->regions_list, list)
> +
> +#define damon_for_each_region_safe(r, next, t) \
> +	list_for_each_entry_safe(r, next, &t->regions_list, list)
> +
> +#define damon_for_each_task(t, ctx) \
> +	list_for_each_entry(t, &(ctx)->tasks_list, list)
> +
> +#define damon_for_each_task_safe(t, next, ctx) \
> +	list_for_each_entry_safe(t, next, &(ctx)->tasks_list, list)
> +
> +/* Get a random number in [l, r) */
> +#define damon_rand(l, r) (l + prandom_u32() % (r - l))
> +
> +/*
> + * Construct a damon_region struct
> + *
> + * Returns the pointer to the new struct if success, or NULL otherwise
> + */
> +static struct damon_region *damon_new_region(struct damon_ctx *ctx,
> +				unsigned long start, unsigned long end)
> +{
> +	struct damon_region *region;
> +
> +	region = kmalloc(sizeof(*region), GFP_KERNEL);
> +	if (!region)
> +		return NULL;
> +
> +	region->ar.start = start;
> +	region->ar.end = end;
> +	region->nr_accesses = 0;
> +	INIT_LIST_HEAD(&region->list);
> +
> +	return region;
> +}
> +
> +/*
> + * Add a region between two other regions
> + */
> +static inline void damon_insert_region(struct damon_region *r,
> +		struct damon_region *prev, struct damon_region *next)
> +{
> +	__list_add(&r->list, &prev->list, &next->list);
> +}
> +
> +static void damon_add_region(struct damon_region *r, struct damon_task *t)
> +{
> +	list_add_tail(&r->list, &t->regions_list);
> +}
> +
> +static void damon_del_region(struct damon_region *r)
> +{
> +	list_del(&r->list);
> +}
> +
> +static void damon_free_region(struct damon_region *r)
> +{
> +	kfree(r);
> +}
> +
> +static void damon_destroy_region(struct damon_region *r)
> +{
> +	damon_del_region(r);
> +	damon_free_region(r);
> +}
> +
> +/*
> + * Construct a damon_task struct
> + *
> + * Returns the pointer to the new struct if success, or NULL otherwise
> + */
> +static struct damon_task *damon_new_task(int pid)
> +{
> +	struct damon_task *t;
> +
> +	t = kmalloc(sizeof(*t), GFP_KERNEL);
> +	if (!t)
> +		return NULL;
> +
> +	t->pid = pid;
> +	INIT_LIST_HEAD(&t->regions_list);
> +
> +	return t;
> +}
> +
> +static void damon_add_task(struct damon_ctx *ctx, struct damon_task *t)
> +{
> +	list_add_tail(&t->list, &ctx->tasks_list);
> +}
> +
> +static void damon_del_task(struct damon_task *t)
> +{
> +	list_del(&t->list);
> +}
> +
> +static void damon_free_task(struct damon_task *t)
> +{
> +	struct damon_region *r, *next;
> +
> +	damon_for_each_region_safe(r, next, t)
> +		damon_free_region(r);
> +	kfree(t);
> +}
> +
> +static void damon_destroy_task(struct damon_task *t)
> +{
> +	damon_del_task(t);
> +	damon_free_task(t);
> +}
> +
> +static unsigned int nr_damon_tasks(struct damon_ctx *ctx)
> +{
> +	struct damon_task *t;
> +	unsigned int nr_tasks = 0;
> +
> +	damon_for_each_task(t, ctx)
> +		nr_tasks++;
> +
> +	return nr_tasks;
> +}
> +
> +static unsigned int nr_damon_regions(struct damon_task *t)
> +{
> +	struct damon_region *r;
> +	unsigned int nr_regions = 0;
> +
> +	damon_for_each_region(r, t)
> +		nr_regions++;
> +
> +	return nr_regions;
> +}
> +
> +/*
> + * Functions for the module loading/unloading
> + */
> +
> +static int __init damon_init(void)
> +{
> +	return 0;
> +}
> +
> +static void __exit damon_exit(void)
> +{
> +}
> +
> +module_init(damon_init);
> +module_exit(damon_exit);
> +
> +MODULE_LICENSE("GPL");
> +MODULE_AUTHOR("SeongJae Park <sjpark@amazon.de>");
> +MODULE_DESCRIPTION("DAMON: Data Access MONitor");
> 




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