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[114.32.231.59]) by smtp.gmail.com with ESMTPSA id b3sm4623185pfp.65.2019.08.29.11.59.03 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Thu, 29 Aug 2019 11:59:04 -0700 (PDT) Date: Fri, 30 Aug 2019 02:59:01 +0800 From: Peikan Tsai To: Christian Brauner Cc: Joel Fernandes , Greg KH , arve@android.com, tkjos@android.com, maco@android.com, devel@driverdev.osuosl.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH] binder: Use kmem_cache for binder_thread Message-ID: <20190829185901.GA4680@mark-All-Series> References: <20190829054953.GA18328@mark-All-Series> <20190829064229.GA30423@kroah.com> <20190829135359.GB63638@google.com> <20190829152721.ttsyfwaeygmwmcu7@wittgenstein> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20190829152721.ttsyfwaeygmwmcu7@wittgenstein> User-Agent: Mutt/1.9.4 (2018-02-28) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On Thu, Aug 29, 2019 at 05:27:22PM +0200, Christian Brauner wrote: > On Thu, Aug 29, 2019 at 09:53:59AM -0400, Joel Fernandes wrote: > > 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? > > Probably SLAB_HWCACHE_ALIGN would make most sense. > Agree. Thanks for yours comments and suggestions. I'll put SLAB_HWCACHE_ALIGN it in patch v2. > > > > > 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! > > Yeah, it'd be interesting to see what difference this actually makes. > > Christian I tested this change on an Android device(arm) with AOSP kernel 4.19 and observed memory usage of binder_thread. But I didn't do binder benchmark yet. On my platform the memory usage of binder_thread reduce about 90 KB as the following result. nr obj obj size total before: 624 512 319488 bytes after: 728 312 227136 bytes