Re: Deadlock possibly caused by too_many_isolated.

[Wu Fengguang <fengguang.wu@intel.com>]

> @@ -2054,10 +2069,11 @@ rebalance:
>                 goto got_pg;
> 
>         /*
> -        * If we failed to make any progress reclaiming, then we are
> -        * running out of options and have to consider going OOM
> +        * If we failed to make any progress reclaiming and there aren't
> +        * many parallel reclaiming, then we are unning out of options and
> +        * have to consider going OOM
>          */
> -       if (!did_some_progress) {
> +       if (!did_some_progress && !too_many_isolated_zone(preferred_zone)) {
>                 if ((gfp_mask & __GFP_FS) && !(gfp_mask & __GFP_NORETRY)) {
>                         if (oom_killer_disabled)
>                                 goto nopage;

This is simply wrong.

It disabled this block for 99% system because there won't be enough
tasks to make (!too_many_isolated_zone == true). As a result the LRU
will be scanned like mad and no task get OOMed when it should be.

Thanks,
Fengguang