Re: [PATCH v2] tools/mm: Add thpmaps script to dump THP usage info

[John Hubbard <jhubbard@nvidia.com>]

On 1/10/24 09:32, Ryan Roberts wrote:
...
> options:
>    -h, --help           show this help message and exit
>    --pid pid            Process id of the target process. Exactly one
>                         of --pid and --cgroup must be provided.
>    --cgroup path        Path to the target cgroup in sysfs. Iterates
>                         over every pid in the cgroup and its children.
>                         Get global stats by passing in the root cgroup

Hi Ryan,

Yes, this version is fairly effective at getting global stats now.

I've got some proposed minor tweaks below, and a few questions. Let me
start with the questions:

1) When I run this on an older 6.4.8-based kernel:

     # ./thpmaps --cgroup /sys/fs/cgroup  --cont 128K --cont 512K --cont 1M \
             --cont 2M --cont 512M --summary

, I get this output:

file-thp-aligned-524288kB:      36175872 kB (95%)
file-thp-partial:                 856640 kB ( 2%)
file-cont-aligned-128kB:        37032320 kB (97%)
file-cont-aligned-512kB:        36597760 kB (96%)
file-cont-aligned-1024kB:       36597760 kB (96%)
file-cont-aligned-2048kB:       36595712 kB (96%)
file-cont-aligned-524288kB:     36175872 kB (95%)


Is it true that the above is basically "normal" 512MB THP in action?
And all of the "cont" entries are just that way because we can't
really tell mTHP/cont apart from normal THP?

2) On an mTHP kernel with the latest patchsets (arm64, 64K page size), I
*think* I cannot turn off mTHP. I'm still teasing apart how much of this
is an instrumentation error, and how much is a measurement problem (with
the test suite). And maybe I'm wrong entirely. But the "never" option
doesn't seem to have an effect. Unless the latest version of the testsuite
is doing something new, sigh.

$ for f in $(find /sys/kernel/mm/transparent_hugepage/ -name enabled); do echo "$f: $(cat $f)"; done
/sys/kernel/mm/transparent_hugepage/hugepages-512kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/enabled: always madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-262144kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-2048kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-32768kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-1024kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-16384kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-524288kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-8192kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-256kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-65536kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-131072kB/enabled: always inherit madvise [never]
/sys/kernel/mm/transparent_hugepage/hugepages-4096kB/enabled: always inherit madvise [never]

Any quick thoughts? Don't waste any time on this, it's probably
operator error. Just in case, though.


>                         (e.g. /sys/fs/cgroup for cgroup-v2 or
>                         /sys/fs/cgroup/pids for cgroup-v1). Exactly one
>                         of --pid and --cgroup must be provided.

Maybe we could add "--global" to that list. That would look, in order,
inside cgroups2 and cgroups, for a list of pids, and then run as if
--cgroup /sys/fs/cgroup or --cgroup /sys/fs/cgroup/pids were specified.

It's nicer than failing out. And it's also directly useful. I would be
running my above command like this, instead:

# ./thpmaps --global  --cont 128K --cont 512K --cont 1M \
             --cont 2M --cont 512M --summary

thanks,
-- 
John Hubbard
NVIDIA