Re: [patch] android, lowmemorykiller: remove task handoff notifier

From: Colin Cross
Date: Mon Apr 09 2012 - 21:23:02 EST


On Mon, Apr 9, 2012 at 4:56 PM, David Rientjes <rientjes@xxxxxxxxxx> wrote:
> The task handoff notifier leaks task_struct since it never gets freed
> after the callback returns NOTIFY_OK, which means it is responsible for
> doing so.
>
> It turns out the lowmemorykiller actually doesn't need this notifier at
> all.  It's used to prevent unnecessary killing by waiting for a thread to
> exit as a result of lowmem_shrink(), however, it's possible to do this in
> the same way the kernel oom killer works by setting TIF_MEMDIE and avoid
> killing if we're still waiting for it to exit.
>
> The kernel oom killer will already automatically set TIF_MEMDIE for
> threads that are attempting to allocate memory that have a fatal signal.
> The thread selected by lowmem_shrink() will have such a signal after the
> lowmemorykiller sends it a SIGKILL, so this won't result in an
> unnecessary use of memory reserves for the thread to exit.
>
> This has the added benefit that we don't have to rely on CONFIG_PROFILING
> to prevent needlessly killing tasks.
>
> Reported-by: werner <w.landgraf@xxxxx>
> Cc: stable@xxxxxxxxxxxxxxx
> Signed-off-by: David Rientjes <rientjes@xxxxxxxxxx>
> ---
>  drivers/staging/android/lowmemorykiller.c |   48 +++++------------------------
>  1 file changed, 7 insertions(+), 41 deletions(-)
>

I did a quick test to measure the difference in time spent inside
lowmem_shrink with and without this patch, and they were about the
same. So,
Acked-by: Colin Cross <ccross@xxxxxxxxxxx>
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