fix: < should be >

[cuiweixie]

According to:

mimalloc/src/arena.c

Line 565 in 8ff03b6

if (!force && (expire == 0 || expire > now)) return false;

should be >, not <.

[res2k]

Are you sure?
Currently, mi_arenas_purge_expire contains a point in time after which arenas should be "purged".
So the condition in question will leave the function (and not do any purging) until that point in time is reached.

With your change, arenas will be purged if the time is not yet at mi_arenas_purge_expire; given that this is usually a time point in the future most of the time, and also updated to a time point in the future when purging, this means purging will happen continuously.
This is probably not how this is intended to work.

[will-extrahop]

@res2k are you sure you're sure? 🙂 Changing to > would mean that we bail out when arenas_expire > now, i.e. when the expiration time has not yet arrived, which is what we want. It would also match the analogous condition in mi_arena_try_purge() on line 565.

[res2k]

@res2k are you sure you're sure?

Uh, well... certainly less now.

In any case, this discussion shed more light on why there may be an issue than the initial PR description, so that's a win.