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[46.139.12.213]) by smtp.gmail.com with ESMTPSA id n15sm2469389wrw.47.2019.10.07.11.24.37 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 07 Oct 2019 11:24:37 -0700 (PDT) Date: Mon, 7 Oct 2019 20:24:35 +0200 From: Ingo Molnar To: kan.liang@linux.intel.com Cc: peterz@infradead.org, acme@kernel.org, linux-kernel@vger.kernel.org, jolsa@kernel.org, namhyung@kernel.org, ak@linux.intel.com, vitaly.slobodskoy@intel.com, pavel.gerasimov@intel.com Subject: Re: [PATCH 00/10] Stitch LBR call stack Message-ID: <20191007182435.GA97660@gmail.com> References: <20191007175910.2805-1-kan.liang@linux.intel.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191007175910.2805-1-kan.liang@linux.intel.com> User-Agent: Mutt/1.10.1 (2018-07-13) Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * kan.liang@linux.intel.com wrote: > Performance impact: > The processing time may increase with the LBR stitching approach > enabled. The impact depends on the number of samples with stitched LBRs. > > For sqlite's tcltest, > perf record --call-graph lbr -- make tcltest > perf report --stitch-lbr > > There are 4.11% samples has stitched LBRs. > Total number of samples: 2833728 > The number of samples with stitched LBRs 116478 > > The processing time of perf report increases 6.8% > Without --stitch-lbr: 55906106 usec > With --stitch-lbr: 59728701 usec > > For a simple test case tchain_edit with 43 depth of call stacks. > perf record --call-graph lbr -- ./tchain_edit > perf report --stitch-lbr > > There are 99.9% samples has stitched LBRs. > Total number of samples: 10915 > The number of samples with stitched LBRs 10905 > > The processing time of perf report increases 67.4% > Without --stitch-lbr: 11970508 usec > With --stitch-lbr: 20036055 usec That cost seems pretty high, while the feature sounds useful - is there any way to speed this up? Thanks, Ingo