From: Joel Fernandes <joel@joelfernandes.org>
To: Greg KH <gregkh@linuxfoundation.org>
Cc: Peikan Tsai <peikantsai@gmail.com>,
arve@android.com, tkjos@android.com, maco@android.com,
christian@brauner.io, devel@driverdev.osuosl.org,
linux-kernel@vger.kernel.org
Subject: Re: [PATCH] binder: Use kmem_cache for binder_thread
Date: Thu, 29 Aug 2019 09:53:59 -0400 [thread overview]
Message-ID: <20190829135359.GB63638@google.com> (raw)
In-Reply-To: <20190829064229.GA30423@kroah.com>
On Thu, Aug 29, 2019 at 08:42:29AM +0200, Greg KH wrote:
> On Thu, Aug 29, 2019 at 01:49:53PM +0800, Peikan Tsai wrote:
[snip]
> > The allocated size for each binder_thread is 512 bytes by kzalloc.
> > Because the size of binder_thread is fixed and it's only 304 bytes.
> > It will save 208 bytes per binder_thread when use create a kmem_cache
> > for the binder_thread.
>
> Are you _sure_ it really will save that much memory? You want to do
> allocations based on a nice alignment for lots of good reasons,
> especially for something that needs quick accesses.
Alignment can be done for slab allocations, kmem_cache_create() takes an
align argument. I am not sure what the default alignment of objects is
though (probably no default alignment). What is an optimal alignment in your
view?
> Did you test your change on a system that relies on binder and find any
> speed improvement or decrease, and any actual memory savings?
>
> If so, can you post your results?
That's certainly worth it and I thought of asking for the same, but spoke too
soon!
Independent note: In general I find the internal fragmentation with large
kmalloc()s troubling in the kernel :-(. Say you have a 5000 objects of 512
allocation, each 300 bytes. 212 * 5000 is around 1MB. Which is arguably not
neglible on a small memory system, right?
thanks,
- Joel
next prev parent reply other threads:[~2019-08-29 13:54 UTC|newest]
Thread overview: 11+ messages / expand[flat|nested] mbox.gz Atom feed top
2019-08-29 5:49 [PATCH] binder: Use kmem_cache for binder_thread Peikan Tsai
2019-08-29 6:42 ` Greg KH
2019-08-29 13:53 ` Joel Fernandes [this message]
2019-08-29 15:27 ` Christian Brauner
2019-08-29 18:59 ` Peikan Tsai
2019-08-29 19:30 ` joel
2019-08-30 6:39 ` Greg KH
2019-09-02 14:12 ` Peikan Tsai
2019-08-30 6:38 ` Greg KH
2019-08-30 12:12 ` Christian Brauner
2019-08-29 13:43 ` Joel Fernandes
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