From: Ingo Molnar Date: Fri, 29 Apr 2011 11:19:47 +0000 (+0200) Subject: perf events: Add generic front-end and back-end stalled cycle event definitions X-Git-Tag: v3.0-rc1~404^2~11^2~9 X-Git-Url: http://git.openpandora.org/cgi-bin/gitweb.cgi?a=commitdiff_plain;h=8f62242246351b5a4bc0c1f00c0c7003edea128a;p=pandora-kernel.git perf events: Add generic front-end and back-end stalled cycle event definitions Add two generic hardware events: front-end and back-end stalled cycles. These events measure conditions when the CPU is executing code but its capabilities are not fully utilized. Understanding such situations and analyzing them is an important sub-task of code optimization workflows. Both events limit performance: most front end stalls tend to be caused by branch misprediction or instruction fetch cachemisses, backend stalls can be caused by various resource shortages or inefficient instruction scheduling. Front-end stalls are the more important ones: code cannot run fast if the instruction stream is not being kept up. An over-utilized back-end can cause front-end stalls and thus has to be kept an eye on as well. The exact composition is very program logic and instruction mix dependent. We use the terms 'stall', 'front-end' and 'back-end' loosely and try to use the best available events from specific CPUs that approximate these concepts. Cc: Peter Zijlstra Cc: Arnaldo Carvalho de Melo Cc: Frederic Weisbecker Link: http://lkml.kernel.org/n/tip-7y40wib8n000io7hjpn1dsrm@git.kernel.org Signed-off-by: Ingo Molnar --- Reading git-diff-tree failed