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From: Gregory Price <gourry.memverge@gmail.com>
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	Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Subject: [PATCH v5 00/11] mempolicy2, mbind2, and weighted interleave
Date: Sat, 23 Dec 2023 13:10:50 -0500
Message-Id: <20231223181101.1954-1-gregory.price@memverge.com>
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Weighted interleave is a new interleave policy intended to make
use of a the new distributed-memory environment made available
by CXL.  The existing interleave mechanism does an even round-robin
distribution of memory across all nodes in a nodemask, while
weighted interleave can distribute memory across nodes according
the available bandwidth that that node provides.

As tests below show, "default interleave" can cause major performance
degredation due to distribution not matching bandwidth available,
while "weighted interleave" can provide a performance increase.

For example, the stream benchmark demonstrates that default interleave
is actively harmful, where weighted interleave is beneficial.

Hardware: 1-socket 8 channel DDR5 + 1 CXL expander in PCIe x16
Default interleave : -78% (slower than DRAM)
Global weighting   : -6% to +4% (workload dependant)
Targeted weights   : +2.5% to +4% (consistently better than DRAM)

If nothing else, this shows how awful round-robin interleave is.

Rather than implement yet another specific syscall to set one
particular field of a mempolicy, we chose to implement an extensible
mempolicy interface so that future extensions can be captured.

To implement weighted interleave, we need an interface to set the
node weights along with a MPOL_WEIGHTED_INTERLEAVE. We implement a
a sysfs extension for "system global" weights which can be set by
a daemon or administrator, and new extensible syscalls (mempolicy2,
mbind2) which allow task-local weights to be set via user-software.

The benefit of the sysfs extension is that MPOL_WEIGHTED_INTERLEAVE
can be used by the existing set_mempolicy and mbind via numactl.

There are 3 "phases" in the patch set that could be considered
for separate merge candidates, but are presented here as a single
line as the goal is a fully functional MPOL_WEIGHTED_INTERLEAVE.

1) Implement MPOL_WEIGHTED_INTERLEAVE with a sysfs extension for
   setting system-global weights via sysfs.
   (Patches 1 & 2)

2) Refactor mempolicy creation mechanism to use an extensible arg
   struct `struct mempolicy_args` to promote code re-use between
   the original mempolicy/mbind interfaces and the new interfaces.
   (Patches 3-6)

3) Implementation of set_mempolicy2, get_mempolicy2, and mbind2,
   along with the addition of task-local weights so that per-task
   weights can be registered for MPOL_WEIGHTED_INTERLEAVE.
   (Patches 7-11)

Included at the bottom of this cover letter is linux test project
tests for backward and forward compatibility, some sample software
which can be used for quick tests, as well as a numactl branch
which implements `numactl -w --interleave` for testing.

= Performance summary =
(tests may have different configurations, see extended info below)
1) MLC (W2) : +38% over DRAM. +264% over default interleave.
   MLC (W5) : +40% over DRAM. +226% over default interleave.
2) Stream   : -6% to +4% over DRAM, +430% over default interleave.
3) XSBench  : +19% over DRAM. +47% over default interleave.

= LTP Testing Summary =
existing mempolicy & mbind tests: pass
mempolicy & mbind + weighted interleave (global weights): pass
mempolicy2 & mbind2 + weighted interleave (global weights): pass
mempolicy2 & mbind2 + weighted interleave (local weights): pass

= v5 (full notes at botton =
- stupid mistake fixing arm64 build (get_mbind2 -> mbind2)
- resolve ABI breakage within patch set.
- remove MPOL_F_NODE functionality from mempolicy2
  Suggested-by: Ying Huang <ying.huang@intel.com>
- Documentation and cover letter updates

=====================================================================
Performance tests - MLC
From - Ravi Jonnalagadda <ravis.opensrc@micron.com>

Hardware: Single-socket, multiple CXL memory expanders.

Workload:                               W2
Data Signature:                         2:1 read:write
DRAM only bandwidth (GBps):             298.8
DRAM + CXL (default interleave) (GBps): 113.04
DRAM + CXL (weighted interleave)(GBps): 412.5
Gain over DRAM only:                    1.38x
Gain over default interleave:           2.64x

Workload:                               W5
Data Signature:                         1:1 read:write
DRAM only bandwidth (GBps):             273.2
DRAM + CXL (default interleave) (GBps): 117.23
DRAM + CXL (weighted interleave)(GBps): 382.7
Gain over DRAM only:                    1.4x
Gain over default interleave:           2.26x

=====================================================================
Performance test - Stream
From - Gregory Price <gregory.price@memverge.com>

Hardware: Single socket, single CXL expander
numactl extension: https://github.com/gmprice/numactl/tree/weighted_interleave_master

Summary: 64 threads, ~18GB workload, 3GB per array, executed 100 times
Default interleave : -78% (slower than DRAM)
Global weighting   : -6% to +4% (workload dependant)
mbind2 weights     : +2.5% to +4% (consistently better than DRAM)

dram only:
numactl --cpunodebind=1 --membind=1 ./stream_c.exe --ntimes 100 --array-size 400M --malloc
Function     Direction    BestRateMBs     AvgTime      MinTime      MaxTime
Copy:        0->0            200923.2     0.032662     0.031853     0.033301
Scale:       0->0            202123.0     0.032526     0.031664     0.032970
Add:         0->0            208873.2     0.047322     0.045961     0.047884
Triad:       0->0            208523.8     0.047262     0.046038     0.048414

CXL-only:
numactl --cpunodebind=1 -w --membind=2 ./stream_c.exe --ntimes 100 --array-size 400M --malloc
Copy:        0->0             22209.7     0.288661     0.288162     0.289342
Scale:       0->0             22288.2     0.287549     0.287147     0.288291
Add:         0->0             24419.1     0.393372     0.393135     0.393735
Triad:       0->0             24484.6     0.392337     0.392083     0.394331

Based on the above, the optimal weights are ~9:1
echo 9 > /sys/kernel/mm/mempolicy/weighted_interleave/node1
echo 1 > /sys/kernel/mm/mempolicy/weighted_interleave/node2

default interleave:
numactl --cpunodebind=1 --interleave=1,2 ./stream_c.exe --ntimes 100 --array-size 400M --malloc
Copy:        0->0             44666.2     0.143671     0.143285     0.144174
Scale:       0->0             44781.6     0.143256     0.142916     0.143713
Add:         0->0             48600.7     0.197719     0.197528     0.197858
Triad:       0->0             48727.5     0.197204     0.197014     0.197439

global weighted interleave:
numactl --cpunodebind=1 -w --interleave=1,2 ./stream_c.exe --ntimes 100 --array-size 400M --malloc
Copy:        0->0            190085.9     0.034289     0.033669     0.034645
Scale:       0->0            207677.4     0.031909     0.030817     0.033061
Add:         0->0            202036.8     0.048737     0.047516     0.053409
Triad:       0->0            217671.5     0.045819     0.044103     0.046755

targted regions w/ global weights (modified stream to mbind2 malloc'd regions))
numactl --cpunodebind=1 --membind=1 ./stream_c.exe -b --ntimes 100 --array-size 400M --malloc
Copy:        0->0            205827.0     0.031445     0.031094     0.031984
Scale:       0->0            208171.8     0.031320     0.030744     0.032505
Add:         0->0            217352.0     0.045087     0.044168     0.046515
Triad:       0->0            216884.8     0.045062     0.044263     0.046982

=====================================================================
Performance tests - XSBench
From - Hyeongtak Ji <hyeongtak.ji@sk.com>

Hardware: Single socket, Single CXL memory Expander

NUMA node 0: 56 logical cores, 128 GB memory
NUMA node 2: 96 GB CXL memory
Threads:     56
Lookups:     170,000,000

Summary: +19% over DRAM. +47% over default interleave.

Performance tests - XSBench
1. dram only
$ numactl -m 0 ./XSBench -s XL –p 5000000
Runtime:     36.235 seconds
Lookups/s:   4,691,618

2. default interleave
$ numactl –i 0,2 ./XSBench –s XL –p 5000000
Runtime:     55.243 seconds
Lookups/s:   3,077,293

3. weighted interleave
numactl –w –i 0,2 ./XSBench –s XL –p 5000000
Runtime:     29.262 seconds
Lookups/s:   5,809,513

=====================================================================
(Patch 1) : sysfs addition - /sys/kernel/mm/mempolicy/

This feature provides a way to set interleave weight information under
sysfs at /sys/kernel/mm/mempolicy/weighted_interleave/

    The sysfs structure is designed as follows.

      $ tree /sys/kernel/mm/mempolicy/
      /sys/kernel/mm/mempolicy/
      └── weighted_interleave
          ├── nodeN
          └── nodeN+X

'mempolicy' is added to '/sys/kernel/mm/' as a control group for
the mempolicy subsystem.

Internally, weights are represented as an array of unsigned char

static unsigned char iw_table[MAX_NUMNODES];

char was chosen as most reasonable distributions can be represented
as factors <100, and to minimize memory usage (1KB)

We present possible nodes, instead of online nodes, to simplify the
management interface, considering that a) the table is of size
MAX_NUMNODES anyway to simplify fetching of weights (no need to track
sizes, and MAX_NUMNODES is typically at most 1kb), and b) it simplifies
management of hotplug events, allowing for weights to be set prior to
a node coming online, which may be beneficial for immediate use.

the 'weight' of a node (an unsigned char of value 1-255) is the number
of pages that are allocated during a "weighted interleave" round.
(See 'weighted interleave' for more details').

=====================================================================
(Patch 2) set_mempolicy: MPOL_WEIGHTED_INTERLEAVE

Weighted interleave is a new memory policy that interleaves memory
across numa nodes in the provided nodemask based on the weights
described in patch 1 (sysfs global weights).

When a system has multiple NUMA nodes and it becomes bandwidth hungry,
the current MPOL_INTERLEAVE could be an wise option.

However, if those NUMA nodes consist of different types of memory such
as having local DRAM and CXL memory together, the current round-robin
based interleaving policy doesn't maximize the overall bandwidth
because of their different bandwidth characteristics.

Instead, the interleaving can be more efficient when the allocation
policy follows each NUMA nodes' bandwidth weight rather than having 1:1
round-robin allocation.

This patch introduces a new memory policy, MPOL_WEIGHTED_INTERLEAVE,
which enables weighted interleaving between NUMA nodes.  Weighted
interleave allows for a proportional distribution of memory across
multiple numa nodes, preferablly apportioned to match the bandwidth
capacity of each node from the perspective of the accessing node.

For example, if a system has 1 CPU node (0), and 2 memory nodes (0,1),
with a relative bandwidth of (100GB/s, 50GB/s) respectively, the
appropriate weight distribution is (2:1).

Weights will be acquired from the global weight array exposed by the
sysfs extension: /sys/kernel/mm/mempolicy/weighted_interleave/

The policy will then allocate the number of pages according to the
set weights.  For example, if the weights are (2,1), then 2 pages
will be allocated on node0 for every 1 page allocated on node1.

The new flag MPOL_WEIGHTED_INTERLEAVE can be used in set_mempolicy(2)
and mbind(2).

=====================================================================
(Patches 3-6) Refactoring mempolicy for code-reuse

To avoid multiple paths of mempolicy creation, we should refactor the
existing code to enable the designed extensibility, and refactor
existing users to utilize the new interface (while retaining the
existing userland interface).

This set of patches introduces a new mempolicy_args structure, which
is used to more fully describe a requested mempolicy - to include
existing and future extensions.

/*
 * Describes settings of a mempolicy during set/get syscalls and
 * kernel internal calls to do_set_mempolicy()
 */
struct mempolicy_args {
    unsigned short mode;            /* policy mode */
    unsigned short mode_flags;      /* policy mode flags */
    int home_node;                  /* mbind: use MPOL_MF_HOME_NODE */
    nodemask_t *policy_nodes;       /* get/set/mbind */
    unsigned char *il_weights;      /* for mode MPOL_WEIGHTED_INTERLEAVE */
};

This arg structure will eventually be utilized by the following
interfaces:
    mpol_new() - new mempolicy creation
    do_get_mempolicy() - acquiring information about mempolicy
    do_set_mempolicy() - setting the task mempolicy
    do_mbind()         - setting a vma mempolicy

do_get_mempolicy() is completely refactored to break it out into
separate functionality based on the flags provided by get_mempolicy(2)
    MPOL_F_MEMS_ALLOWED: acquires task->mems_allowed
    MPOL_F_ADDR: acquires information on vma policies
    MPOL_F_NODE: changes the output for the policy arg to node info

We refactor the get_mempolicy syscall flatten the logic based on these
flags, and aloow for set_mempolicy2() to re-use the underlying logic.

The result of this refactor, and the new mempolicy_args structure, is
that extensions like 'sys_set_mempolicy_home_node' can now be directly
integrated into the initial call to 'set_mempolicy2', and that more
complete information about a mempolicy can be returned with a single
call to 'get_mempolicy2', rather than multiple calls to 'get_mempolicy'


=====================================================================
(Patches 7-10) set_mempolicy2, get_mempolicy2, mbind2

These interfaces are the 'extended' counterpart to their relatives.
They use the userland 'struct mpol_args' structure to communicate a
complete mempolicy configuration to the kernel.  This structure
looks very much like the kernel-internal 'struct mempolicy_args':

struct mpol_args {
        /* Basic mempolicy settings */
        __u16 mode;
        __u16 mode_flags;
        __s32 home_node;
        __u64 pol_maxnodes;
        __aligned_u64 pol_nodes;
        __aligned_u64 *il_weights;      /* of size pol_maxnodes */
};

The basic mempolicy settings which are shared across all interfaces
are captured at the top of the structure, while extensions such as
'policy_node' and 'addr' are collected beneath.

The syscalls are uniform and defined as follows:

long sys_mbind2(unsigned long addr, unsigned long len,
                struct mpol_args *args, size_t usize,
                unsigned long flags);

long sys_get_mempolicy2(struct mpol_args *args, size_t size,
                        unsigned long addr, unsigned long flags);

long sys_set_mempolicy2(struct mpol_args *args, size_t size,
                        unsigned long flags);

The 'flags' argument for mbind2 is the same as 'mbind', except with
the addition of MPOL_MF_HOME_NODE to denote whether the 'home_node'
field should be utilized.

The 'flags' argument for get_mempolicy2 allows for MPOL_F_ADDR to
allow operating on VMA policies, but MPOL_F_NODE and MPOL_F_MEMS_ALLOWED
behavior has been omitted, since get_mempolicy() provides this already.

The 'flags' argument is not used by 'set_mempolicy' at this time, but
may end up allowing the use of MPOL_MF_HOME_NODE if such functionality
is desired.

The extensions can be summed up as follows:

get_mempolicy2 extensions:
    - mode and mode flags are split into separate fields
    - MPOL_F_MEMS_ALLOWED and MPOL_F_NODE are not supported

set_mempolicy2:
    - task-local interleave weights can be set via 'il_weights'

mbind2:
    - home_node field sets policy home node w/ MPOL_MF_HOME_NODE
    - task-local interleave weights can be set via 'il_weights'

=====================================================================
(Patch 11) set_mempolicy2/mbind2: MPOL_WEIGHTED_INTERLEAVE

This patch shows the explicit extension pattern when adding new
policies to mempolicy2/mbind2.  This adds the 'il_weights' field
to mpol_args and adds the logic to fill in task-local weights.

There are now two ways to weight a mempolicy: global and local.
To denote which mode the task is in, we add the internal flag:

MPOL_F_GWEIGHT /* Utilize global weights */

When MPOL_F_GWEIGHT is set, the global weights are used, and
when it is not set, task-local weights are used.

Example logic:
if (pol->flags & MPOL_F_GWEIGHT)
       pol_weights = iw_table;
else
       pol_weights = pol->wil.weights;

set_mempolicy is changed to always set MPOL_F_GWEIGHT, since this
syscall is incapable of passing weights via its interfaces, while
set_mempolicy2 sets MPOL_F_GWEIGHT if MPOL_WEIGHTED_INTERLEAVE
is requested but 'il_weights' in mpol_args is NULL.

The operation of task-local weighted is otherwise exactly the
same - except for what occurs on task migration.

On task migration, the system presently has no way of determining
what the new weights "should be", or what the user "intended".

For this reason, we default all weights to '1' and do not allow
weights to be '0'.  This means, should a migration occur where
one or more new nodes appear in the nodemask - the effective weight
for that node will be '1'.  This avoids a potential allocation
failure condition if a migration occurs and introduces a node
which otherwise did not have a weight.

For this reason, users should use task-local weighting when
migrations are not expected/possible, and global weighting when
migrations are expected/possible.

=====================================================================
Existing LTP Tests: https://github.com/gmprice/ltp/tree/mempolicy2

LTP set_mempolicy, get_mempolicy, mbind regression tests:

MPOL_WEIGHTED_INTERLEAVE added manually to test basic functionality
but did not adjust tests for weighting.  Basically the weights were
set to 1, which is the default, and it should behavior like standard
MPOL_INTERLEAVE if logic is correct.

== set_mempolicy01
passed   18
failed   0

== set_mempolicy02
passed   10
failed   0

== set_mempolicy03
passed   64
failed   0

== set_mempolicy04
passed   32
failed   0

== set_mempolicy05 - n/a on non-x86

== set_mempolicy06 - set_mempolicy02 + MPOL_WEIGHTED_INTERLEAVE
passed   10
failed   0

== set_mempolicy07 - set_mempolicy04 + MPOL_WEIGHTED_INTERLEAVE
passed   32
failed   0

== get_mempolicy01 - added MPOL_WEIGHTED_INTERLEAVE
passed   12
failed   0

== get_mempolicy02
passed   2
failed   0

== mbind01 - added WEIGHTED_INTERLEAVE
passed   15
failed   0

== mbind02 - added WEIGHTED_INTERLEAVE
passed   4
failed   0

== mbind03 - added WEIGHTED_INTERLEAVE
passed   16
failed   0

== mbind04 - added WEIGHTED_INTERLEAVE
passed   48
failed   0

=====================================================================
New LTP Tests: https://github.com/gmprice/ltp/tree/mempolicy2

set_mempolicy2, get_mempolicy2, mbind2

Took the original set_mempolicy and get_mempolicy tests, and updated
them to utilize the new mempolicy2 interfaces.  Added additional tests
for setting task-local weights to validate behavior.

== set_mempolicy201 - set_mempolicy01 equiv
passed   18
failed   0

== set_mempolicy202 - set_mempolicy02 equiv
passed   10
failed   0

== set_mempolicy203 - set_mempolicy03 equiv
passed   64
failed   0

== set_mempolicy204 - set_mempolicy04 equiv
passed   32
failed   0

== set_mempolicy205 - set_mempolicy06 equiv
passed   10
failed   0

== set_mempolicy206 - set_mempolicy07 equiv
passed   32
failed   0

== set_mempolicy207 - MPOL_WEIGHTED_INTERLEAVE with task-local weights
passed   6
failed   0

== get_mempolicy201 - get_mempolicy01 equiv
passed   12
failed   0

== get_mempolicy202 - get_mempolicy02 equiv
passed   2
failed   0

== get_mempolicy203 - NEW - fetch global and local weights
passed   6
failed   0

== mbind201 - mbind01 equiv
passed   15
failed   0

== mbind202 - mbind02 equiv
passed   4
failed   0

== mbind203 - mbind03 equiv
passed   16
failed   0

== mbind204 - mbind04 equiv
passed   48
failed   0

=====================================================================
Basic set_mempolicy2 test

set_mempolicy2 w/ weighted interleave, task-local weights and uses
pthread_create to demonstrate the mempolicy is overwritten by child.

Manually validating the distribution via numa_maps

007c0000 weighted interleave:0-1 heap anon=65794 dirty=65794 active=0 N0=54829 N1=10965 kernelpagesize_kB=4
7f3f2c000000 weighted interleave:0-1 anon=32768 dirty=32768 active=0 N0=5461 N1=27307 kernelpagesize_kB=4
7f3f34000000 weighted interleave:0-1 anon=16384 dirty=16384 active=0 N0=2731 N1=13653 kernelpagesize_kB=4
7f3f3bffe000 weighted interleave:0-1 anon=65538 dirty=65538 active=0 N0=10924 N1=54614 kernelpagesize_kB=4
7f3f5c000000 weighted interleave:0-1 anon=16384 dirty=16384 active=0 N0=2731 N1=13653 kernelpagesize_kB=4
7f3f60dfe000 weighted interleave:0-1 anon=65537 dirty=65537 active=0 N0=54615 N1=10922 kernelpagesize_kB=4

Expected distribution is 5:1 or 1:5 (less node should be ~16.666%)
1) 10965/65794 : 16.6656... pass
2) 5461/32768  : 16.6656... pass
3) 2731/16384  : 16.6687... pass
4) 10924/65538 : 16.6682... pass
5) 2731/16384  : 16.6687... pass
6) 10922/65537 : 16.6653... pass


#define _GNU_SOURCE
#include <stdio.h>
#include <stdlib.h>
#include <numa.h>
#include <errno.h>
#include <numaif.h>
#include <unistd.h>
#include <pthread.h>
#include <sys/uio.h>
#include <sys/types.h>
#include <stdint.h>

#define MPOL_WEIGHTED_INTERLEAVE 6
#define SET_MEMPOLICY2(a, b) syscall(457, a, b, 0)

#define M256 (1024*1024*256)
#define PAGE_SIZE (4096)

struct mpol_args {
        /* Basic mempolicy settings */
        uint16_t mode;
        uint16_t mode_flags;
        int32_t home_node;
        uint64_t pol_maxnodes;
        uint64_t pol_nodes;
        uint64_t il_weights;
};

struct mpol_args wil_args;
struct bitmask *wil_nodes;
unsigned char *weights;
int total_nodes = -1;
pthread_t tid;

void set_mempolicy_call(int which)
{
        weights = (unsigned char *)calloc(total_nodes, sizeof(unsigned char));
        wil_nodes = numa_allocate_nodemask();

        numa_bitmask_setbit(wil_nodes, 0); weights[0] = which ? 1 : 5;
        numa_bitmask_setbit(wil_nodes, 1); weights[1] = which ? 5 : 1;

        memset(&wil_args, 0, sizeof(wil_args));
        wil_args.mode = MPOL_WEIGHTED_INTERLEAVE;
        wil_args.mode_flags = 0;
        wil_args.pol_nodes = wil_nodes->maskp;
        wil_args.pol_maxnodes = total_nodes;
        wil_args.il_weights = weights;

        int ret = SET_MEMPOLICY2(&wil_args, sizeof(wil_args));
        fprintf(stderr, "set_mempolicy2 result: %d(%s)\n", ret, strerror(errno));
}

void *func(void *arg)
{
        char *mainmem = malloc(M256);
        int i;

        set_mempolicy_call(1); /* weight 1 heavier */

        mainmem = malloc(M256);
        memset(mainmem, 1, M256);
        for (i = 0; i < (M256/PAGE_SIZE); i++) {
                mainmem = malloc(PAGE_SIZE);
                mainmem[0] = 1;
        }
        printf("thread done %d\n", getpid());
        getchar();
        return arg;
}

int main()
{
        char * mainmem;
        int i;

        total_nodes = numa_max_node() + 1;

        set_mempolicy_call(0); /* weight 0 heavier */
        pthread_create(&tid, NULL, func, NULL);

        mainmem = malloc(M256);
        memset(mainmem, 1, M256);
        for (i = 0; i < (M256/PAGE_SIZE); i++) {
                mainmem = malloc(PAGE_SIZE);
                mainmem[0] = 1;
        }
        printf("main done %d\n", getpid());
        getchar();

        return 0;
}

=====================================================================
numactl (set_mempolicy) w/ global weighting test
numactl fork: https://github.com/gmprice/numactl/tree/weighted_interleave_master

command: numactl -w --interleave=0,1 ./eatmem

result (weights 1:1):
0176a000 weighted interleave:0-1 heap anon=65793 dirty=65793 active=0 N0=32897 N1=32896 kernelpagesize_kB=4
7fceeb9ff000 weighted interleave:0-1 anon=65537 dirty=65537 active=0 N0=32768 N1=32769 kernelpagesize_kB=4
50% distribution is correct

result (weights 5:1):
01b14000 weighted interleave:0-1 heap anon=65793 dirty=65793 active=0 N0=54828 N1=10965 kernelpagesize_kB=4
7f47a1dff000 weighted interleave:0-1 anon=65537 dirty=65537 active=0 N0=54614 N1=10923 kernelpagesize_kB=4
16.666% distribution is correct

result (weights 1:5):
01f07000 weighted interleave:0-1 heap anon=65793 dirty=65793 active=0 N0=10966 N1=54827 kernelpagesize_kB=4
7f17b1dff000 weighted interleave:0-1 anon=65537 dirty=65537 active=0 N0=10923 N1=54614 kernelpagesize_kB=4
16.666% distribution is correct

#include <stdio.h>
#include <stdlib.h>
#include <string.h>
int main (void)
{
        char* mem = malloc(1024*1024*256);
        memset(mem, 1, 1024*1024*256);
        for (int i = 0; i  < ((1024*1024*256)/4096); i++)
        {
                mem = malloc(4096);
                mem[0] = 1;
        }
        printf("done\n");
        getchar();
        return 0;
}

=====================================================================
v4:
- CONFIG_MMU COND_SYSCALL fix for mempolicy2/mbind2 syscalls
- ifdef CONFIG_SYSFS handling.  If sysfs is disabled, set global
  weights to 1 to have it default to standard interleave.
- tools/perf config variation syscall table fix
- sysfs attr init build fix
- arch/arm64 syscall wire-ups (Thanks Arnd!)

=====================================================================
v3:
  changes / adds:
- get2(): actually fetch the il_weights (doh!)
- get2(): retrieve home_node
- get2(): addr as arg instead of struct member, drop MPOL_F_NODE flag
          get_mempolicy() can be used for this, don't duplicate warts
- get2(): only copy weights if mode is weighted interleave
- mbind2(): addr/len instead of iovec
            user can use a for loop...
- sysfs: remove possible_nodes
- sysfs: simplify to weighted_interleave/nodeN
- sysfs: add default weight mechanism (echo > nodeN)

  fixes:
- build: syscalls.h mpol_args definition missing
- build: missing `__user` from weights_ptr definition
- bug:   uninitialized weight_total in bulk allocator
- bug:   bad pointer to copy_struct_from_user in mbind2
- bug:   get_mempolicy2 uninitialized data copied to user
- bug:   get_vma_mempolicy policy reference counting
- bug:   MPOL_F_GWEIGHTS not set correctly in set_mempolicy2
- bug:   MPOL_F_GWEIGHTS not set correctly in mbind2
- bug:   get_mempolicy2 error not checked on nodemask userland copy
- bug:   mbind2 did not parse nodemask correctly

  tests:
- ltp branch: https://github.com/gmprice/ltp/tree/mempolicy2
- new set_mempolicy2() tests
     1) set_mempolicy() tests w/ new syscall
     2) weighted interleave validation
- new get_mempolicy2() tests
     1) get_mempolicy() tests w/ new syscall
     2) weighted interleave validation
- new mbind2() tests
     1) mbind() tests w/ new syscall
- new performance tests (MLC) from Ravi @ Micron
     Example:
        Workload:                               W5
        Data Signature:                         1:1 read:write
        DRAM only bandwidth (GBps):             273.2
        DRAM + CXL (default interleave) (GBps): 117.23
        DRAM + CXL (weighted interleave)(GBps): 382.7
        Gain over DRAM only:                    1.4x

=====================================================================
v2:
  changes / adds:
- flatted weight matrix to an array at requested of Ying Huang
- Updated ABI docs per Davidlohr Bueso request
- change uapi structure to use aligned/fixed-length members
- Implemented weight fetch logic in get_mempolicy2
- mbind2 was changed to take (iovec,len) as function arguments
  rather than add them to the uapi structure, since they describe
  where to apply the mempolicy - as opposed to being part of it.

  fixes:
- fixed bug reported by Seungjun Ha <seungjun.ha@samsung.com>
  Link: https://lore.kernel.org/linux-cxl/20231206080944epcms2p76ebb230b9f4595f5cfcd2531d67ab3ce@epcms2p7/
- fixed bug in mbind2 where MPOL_F_GWEIGHTS was not set when il_weights
  was omitted after local weights were added as an option
- fixed bug in interleave logic where an OOB access was made if
  next_node_in returned MAX_NUMNODES
- fixed bug in bulk weighted interleave allocator where over-allocation
  could occur.

  tests:
- LTP: validated existing get_mempolicy, set_mempolicy, and mbind tests
- LTP: validated existing get_mempolicy, set_mempolicy, and mbind with
       MPOL_WEIGHTED_INTERLEAVE added.
- basic set_mempolicy2 tests and numactl -w --interleave tests

  numactl:
- Sample numactl extension for set_mempolicy available here:
  Link: https://github.com/gmprice/numactl/tree/weighted_interleave_master

(added summary of test reports to end of cover letter)

=====================================================================

Suggested-by: Gregory Price <gregory.price@memverge.com>
Suggested-by: Johannes Weiner <hannes@cmpxchg.org>
Suggested-by: Hasan Al Maruf <hasanalmaruf@fb.com>
Suggested-by: Hao Wang <haowang3@fb.com>
Suggested-by: Ying Huang <ying.huang@intel.com>
Suggested-by: Dan Williams <dan.j.williams@intel.com>
Suggested-by: Michal Hocko <mhocko@suse.com>
Suggested-by: tj <tj@kernel.org>
Suggested-by: Zhongkun He <hezhongkun.hzk@bytedance.com>
Suggested-by: Frank van der Linden <fvdl@google.com>
Suggested-by: John Groves <john@jagalactic.com>
Suggested-by: Vinicius Tavares Petrucci <vtavarespetr@micron.com>
Suggested-by: Srinivasulu Thanneeru <sthanneeru@micron.com>
Suggested-by: Ravi Jonnalagadda <ravis.opensrc@micron.com>
Suggested-by: Jonathan Cameron <Jonathan.Cameron@Huawei.com>
Suggested-by: Hyeongtak Ji <hyeongtak.ji@sk.com>
Signed-off-by: Gregory Price <gregory.price@memverge.com>

Gregory Price (10):
  mm/mempolicy: introduce MPOL_WEIGHTED_INTERLEAVE for weighted
    interleaving
  mm/mempolicy: refactor sanitize_mpol_flags for reuse
  mm/mempolicy: create struct mempolicy_args for creating new
    mempolicies
  mm/mempolicy: refactor kernel_get_mempolicy for code re-use
  mm/mempolicy: allow home_node to be set by mpol_new
  mm/mempolicy: add userland mempolicy arg structure
  mm/mempolicy: add set_mempolicy2 syscall
  mm/mempolicy: add get_mempolicy2 syscall
  mm/mempolicy: add the mbind2 syscall
  mm/mempolicy: extend set_mempolicy2 and mbind2 to support weighted
    interleave

Rakie Kim (1):
  mm/mempolicy: implement the sysfs-based weighted_interleave interface

 .../ABI/testing/sysfs-kernel-mm-mempolicy     |   4 +
 ...fs-kernel-mm-mempolicy-weighted-interleave |  22 +
 .../admin-guide/mm/numa_memory_policy.rst     |  67 ++
 arch/alpha/kernel/syscalls/syscall.tbl        |   3 +
 arch/arm/tools/syscall.tbl                    |   3 +
 arch/arm64/include/asm/unistd.h               |   2 +-
 arch/arm64/include/asm/unistd32.h             |   6 +
 arch/m68k/kernel/syscalls/syscall.tbl         |   3 +
 arch/microblaze/kernel/syscalls/syscall.tbl   |   3 +
 arch/mips/kernel/syscalls/syscall_n32.tbl     |   3 +
 arch/mips/kernel/syscalls/syscall_o32.tbl     |   3 +
 arch/parisc/kernel/syscalls/syscall.tbl       |   3 +
 arch/powerpc/kernel/syscalls/syscall.tbl      |   3 +
 arch/s390/kernel/syscalls/syscall.tbl         |   3 +
 arch/sh/kernel/syscalls/syscall.tbl           |   3 +
 arch/sparc/kernel/syscalls/syscall.tbl        |   3 +
 arch/x86/entry/syscalls/syscall_32.tbl        |   3 +
 arch/x86/entry/syscalls/syscall_64.tbl        |   3 +
 arch/xtensa/kernel/syscalls/syscall.tbl       |   3 +
 include/linux/mempolicy.h                     |  18 +
 include/linux/syscalls.h                      |   8 +
 include/uapi/asm-generic/unistd.h             |   8 +-
 include/uapi/linux/mempolicy.h                |  16 +-
 kernel/sys_ni.c                               |   3 +
 mm/mempolicy.c                                | 932 +++++++++++++++---
 .../arch/mips/entry/syscalls/syscall_n64.tbl  |   3 +
 .../arch/powerpc/entry/syscalls/syscall.tbl   |   3 +
 .../perf/arch/s390/entry/syscalls/syscall.tbl |   3 +
 .../arch/x86/entry/syscalls/syscall_64.tbl    |   3 +
 29 files changed, 1024 insertions(+), 116 deletions(-)
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-mempolicy
 create mode 100644 Documentation/ABI/testing/sysfs-kernel-mm-mempolicy-weighted-interleave

-- 
2.39.1