Re: [PATCH v4 01/10] Use IDR to maintain all the enabled sources' paths. - Greg Kroah-Hartman

From: Greg Kroah-Hartman <gregkh@linuxfoundation.org>
To: Jinlong Mao <quic_jinlmao@quicinc.com>
Cc: Mathieu Poirier <mathieu.poirier@linaro.org>,
	Suzuki K Poulose <suzuki.poulose@arm.com>,
	Alexander Shishkin <alexander.shishkin@linux.intel.com>,
	Mike Leach <mike.leach@linaro.org>, Leo Yan <leo.yan@linaro.org>,
	coresight@lists.linaro.org, linux-arm-kernel@lists.infradead.org,
	linux-kernel@vger.kernel.org,
	Tingwei Zhang <quic_tingweiz@quicinc.com>,
	Yuanfang Zhang <quic_yuanfang@quicinc.com>,
	Tao Zhang <quic_taozha@quicinc.com>,
	Trilok Soni <quic_tsoni@quicinc.com>,
	Hao Zhang <quic_hazha@quicinc.com>,
	linux-arm-msm@vger.kernel.org
Subject: Re: [PATCH v4 01/10] Use IDR to maintain all the enabled sources' paths.
Date: Thu, 24 Mar 2022 18:06:50 +0100	[thread overview]
Message-ID: <YjylKhBslN+5sKRx@kroah.com> (raw)
In-Reply-To: <e78ff137-fc5e-ff00-0e57-91304288d860@quicinc.com>

On Thu, Mar 24, 2022 at 10:23:19PM +0800, Jinlong Mao wrote:
> Hi Greg,
> 
> Thanks for your review.
> 
> On 3/24/2022 8:26 PM, Greg Kroah-Hartman wrote:
> > On Thu, Mar 24, 2022 at 08:17:25PM +0800, Mao Jinlong wrote:
> > > Use hash length of the source's device name to map to the pointer
> > > of the enabled path. Using IDR will be more efficient than using
> > > the list. And there could be other sources except STM and CPU etms
> > > in the new HWs. It is better to maintain all the paths together.
> > > 
> > > Signed-off-by: Mao Jinlong <quic_jinlmao@quicinc.com>
> > > ---
> > >   drivers/hwtracing/coresight/coresight-core.c | 75 +++++++-------------
> > >   1 file changed, 26 insertions(+), 49 deletions(-)
> > Your subject line is odd.  Please put back the driver subsystem in the
> > subject line so that it makes more sense.
> I will update the subject in next version.
> > 
> > And how have you measured "more efficient"?
> 
> Using IDR would be better than doing a sequential search as there will be
> much more device  in future.

How many "more"?  Where does the trade off of speed for complexity help?
How much faster is this really?  You can't claim performance
improvements without any proof :)

thanks,

greg k-h