Messages in this thread | | | Subject | Re: [PATCH 07/12] perf_events: add LBR software filter support for Intel X86 (v2) | From | Peter Zijlstra <> | Date | Mon, 05 Dec 2011 23:29:40 +0100 |
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On Fri, 2011-10-14 at 14:37 +0200, Stephane Eranian wrote: > > This patch adds an internal sofware filter to complement > the (optional) LBR hardware filter. > > The software filter is necessary: > - as a substitute when there is no HW LBR filter (e.g., Atom, Core) > - to complement HW LBR filter in case of errata (e.g., Nehalem/Westmere) > - to provide finer grain filtering (e.g., all processors) > > Sometimes, the LBR HW filter cannot distinguish between two types > of branches. For instance, to capture syscall as CALLS, it is necessary > to enable the LBR_FAR filter which will also capture JMP instructions. > Thus, a second pass is necessary to filter those out, this is what the > SW filter can do. > > The SW filter is built on top of the internal x86 disassembler. It > is a best effort filter especially for user level code. It is subject > to the availability of the text page of the program. > > The SW filter is enabled on all Intel X86 processors. It is bypassed > when the user is capturing all branches at all priv levels.
This patch is very seriously whitespace challenged.
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