From mboxrd@z Thu Jan 1 00:00:00 1970 From: Chintan Pandya Subject: Re: [PATCH] of: use hash based search in of_find_node_by_phandle Date: Fri, 26 Jan 2018 12:52:43 +0530 Message-ID: References: <1516875247-19599-1-git-send-email-cpandya@codeaurora.org> Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: Content-Language: en-US Sender: linux-kernel-owner@vger.kernel.org To: Rob Herring Cc: Frank Rowand , "open list:OPEN FIRMWARE AND FLATTENED DEVICE TREE BINDINGS" , "linux-kernel@vger.kernel.org" , linux-arm-msm List-Id: devicetree@vger.kernel.org On 1/25/2018 8:20 PM, Rob Herring wrote: > On Thu, Jan 25, 2018 at 4:14 AM, Chintan Pandya wrote: >> of_find_node_by_phandle() takes a lot of time finding > Got some numbers for what is "a lot of time"? On my SDM device, I see total saving of 400ms during boot time. For some clients whose node is quite deeper, they see 1ms time taken by this API. > >> right node when your intended device is too right-side >> in the fdt. Reason is, we search each device serially >> from the fdt, starting from left-most to right-most. > By right side, you mean a deep path? Yes, will correct this if original is confusing. > >> Implement, device-phandle relation in hash-table so >> that look up can be faster. >> >> Change-Id: I4a2bc7eff6de142e4f91a7bf474893a45e61c128 > Run checkpatch.pl Sure. My bad. > >> @@ -61,6 +62,7 @@ struct device_node { >> struct kobject kobj; >> unsigned long _flags; >> void *data; >> + struct hlist_node hash; > Always base your patches on the latest -rc at least. This won't apply. Ok, sure. > > This grows struct device_node for every single node which we recently > worked on to shrink (which is why this won't apply). So I'm now > sensitive to anything that grows it. I'd really prefer something out > of band. > > I'd guess that there's really only a few phandle lookups that occur > over and over. On my system, there are ~6.7k calls of this API during boot. > The clock controller, interrupt controller, etc. What > if you just had a simple array of previously found nodes for a cache > and of_find_node_by_phandle can check that array first. Probably 8-16 > entries would be enough. I clearly see repeat calling with same phandle. But I have few hundreds of nodes. I see hashing as generic optimization which applies equally good to all sized DT. Using ~4KB more size to save 400 ms is a good trade-off, I believe. Chintan Pandya -- The Qualcomm Innovation Center, Inc. is a member of the Code Aurora Forum, a Linux Foundation Collaborative Project