Re: Re: [PATCH v6 0/7] introduce memory hinting API for external process

From: SeongJae Park
Date: Thu Feb 20 2020 - 04:17:16 EST

On Wed, 19 Feb 2020 12:01:23 -0800 Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> wrote:

> On Tue, 18 Feb 2020 17:44:26 -0800 Minchan Kim <minchan@xxxxxxxxxx> wrote:
> > Now, we have MADV_PAGEOUT and MADV_COLD as madvise hinting API. With that,
> > application could give hints to kernel what memory range are preferred to be
> > reclaimed. However, in some platform(e.g., Android), the information
> > required to make the hinting decision is not known to the app.
> > Instead, it is known to a centralized userspace daemon(e.g., ActivityManagerService),
> > and that daemon must be able to initiate reclaim on its own without any app
> > involvement.
> >
> This patchset doesn't seem to be getting a lot of interest from other
> potential users? It seems very specialized. Are there or will there
> ever be any users of this apart from one Android daemon?
> Also, it doesn't terribly hard for ActivityManagerService to tell
> another process "now run madvise with these arguments". Please explain
> why this is not practical in ActivityManagerService and also within
> other potential users of this syscall.

I personally have interest in and hope successful development/merge of this

The interested usecases of 'madvise_process()' for me is optimizations of
general memory-intensive workloads having dynamic data access patterns on
hierarchical memory systems (e.g., multi-tier memory or fast storage based swap
devices). In more detail, I'm already using a part of this patchset for my RFC
patchset implementing Data Access Monitoring-based Operation Schemes[1]. For
my specific case, I don't need new system call but only target task argument,

Once in a past, before joining my current company, I tried using 'madvise()' to
optimize some scientific HPC programs. The improvement results were clear, but
optimizing each of the workloads was challenging and time-consuming. I believe
this new systemcall to be very helpful for such cases, either.


SeongJae Park