Re: [RFC PATCH 0/5] kmalloc-reclaimable caches

On Thu, May 24, 2018 at 01:00:06PM +0200, Vlastimil Babka wrote:

Hi,

as discussed at LSF/MM [1] here's a RFC patchset that introduces
kmalloc-reclaimable caches (more details in the first patch) and uses them
for SLAB freelists and dcache external names. The latter allows us to
repurpose the NR_INDIRECTLY_RECLAIMABLE_BYTES counter later in the series.

This is how /proc/slabinfo looks like after booting in virtme:

...
kmalloc-reclaimable-4194304      0      0 4194304    1 1024 : tunables    1    1    0 : slabdata      0      0      0
...
kmalloc-reclaimable-96     17     64    128   32    1 : tunables  120   60    8 : slabdata      2      2      0
kmalloc-reclaimable-64     50    128     64   64    1 : tunables  120   60    8 : slabdata      2      2      6
kmalloc-reclaimable-32      0      0     32  124    1 : tunables  120   60    8 : slabdata      0      0      0
kmalloc-4194304        0      0 4194304    1 1024 : tunables    1    1    0 : slabdata      0      0      0
...
kmalloc-64          2888   2944     64   64    1 : tunables  120   60    8 : slabdata     46     46    454
kmalloc-32          4325   4712     32  124    1 : tunables  120   60    8 : slabdata     38     38    563
kmalloc-128         1178   1216    128   32    1 : tunables  120   60    8 : slabdata     38     38    114
...

/proc/vmstat with new/renamed nr_reclaimable counter (patch 4):

...
nr_slab_reclaimable 2817
nr_slab_unreclaimable 1781
...
nr_reclaimable 2817
...

/proc/meminfo with exposed nr_reclaimable counter (patch 5):

...
AnonPages:          8624 kB
Mapped:             3340 kB
Shmem:               564 kB
Reclaimable:       11272 kB
Slab:              18368 kB
SReclaimable:      11272 kB
SUnreclaim:         7096 kB
KernelStack:        1168 kB
PageTables:          448 kB
...

Now for the issues a.k.a. why RFC:

- I haven't find any other obvious users for reclaimable kmalloc (yet)

As I remember, ION memory allocator was discussed related to this theme:
https://lkml.org/lkml/2018/4/24/1288

I did a superset as IIRC somebody suggested that in the older threads or at LSF.

This looks nice to me!

Thanks!