Dynamic pool creation has been supported for a long time, which maybe
not used so much in practice. But with the per-memcg lru merged, the
current structure of zswap_pool's lru and shrinker become less optimal.
In the current structure, each zswap_pool has its own lru, shrinker and
shrink_work, but only the latest zswap_pool will be the current used.
1. When memory has pressure, all shrinkers of zswap_pools will try to
shrink its lru list, there is no order between them.
2. When zswap limit hit, only the last zswap_pool's shrink_work will
try to shrink its own lru, which is inefficient.
A more natural way is to have a global zswap lru shared between all
zswap_pools, and so is the shrinker. The code becomes much simpler too.
Another optimization is changing zswap_pool kref to percpu_ref, which
will be taken reference by every zswap entry. So the scalability is
better.
Testing kernel build in tmpfs with memory.max=2GB (zswap shrinker and
writeback enabled with one 50GB swapfile).
mm-unstable zswap-global-lru
real 63.20 63.12
user 1061.75 1062.95
sys 268.74 264.44
Signed-off-by: Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
---
Chengming Zhou (2):
mm/zswap: global lru and shrinker shared by all zswap_pools
mm/zswap: change zswap_pool kref to percpu_ref
mm/zswap.c | 183 +++++++++++++++++++++++++------------------------------------
1 file changed, 76 insertions(+), 107 deletions(-)
---
base-commit: 191d97734e41a5c9f90a2f6636fdd335ae1d435d
change-id: 20240210-zswap-global-lru-94d49316178b
Best regards,
--
Chengming Zhou <zhouchengming@xxxxxxxxxxxxx>
