Re: [PATCH] sysctl: Add a feature to drop caches selectively

From: Pavel Machek
Date: Wed Jun 25 2014 - 18:16:21 EST


On Wed 2014-06-25 10:25:05, Thomas Knauth wrote:
> On Wed, Jun 25, 2014 at 8:25 AM, Artem Bityutskiy <dedekind1@xxxxxxxxx> wrote:
> > Plus some explanations WRT why proc-based interface and what would be
> > the alternatives, what if tomorrow we want to extend the functionality
> > and drop caches only for certain file range, is this only for regular
> > files or also for directories, why posix_fadvice(DONTNEED) is not
> > sufficient.
>
> I suggested the idea originally. Let me address each of your questions in turn:
>
> Why a selective drop? To have a middle ground between echo 2 >
> drop_caches and echo 3 > drop_caches. When is this interesting? My
> particular use case was benchmarking. I wanted to repeatedly measure
> the timing when things were read from disk. Dropping everything from
> the cache, also drops useful things, not just the few files your
> benchmark intends to measure.
>
> Why /proc? Because this is where the current drop_caches mechanism is
> located. If it should go somewhere else, please do suggest so.

It sounds like this should be a new syscall.

echoing filenames in files is strange/ugly.
Pavel
--
(english) http://www.livejournal.com/~pavelmachek
(cesky, pictures) http://atrey.karlin.mff.cuni.cz/~pavel/picture/horses/blog.html
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at http://vger.kernel.org/majordomo-info.html
Please read the FAQ at http://www.tux.org/lkml/