From ee3ed4b45edd66c6e0455d3fab08a48e7ea83030 Mon Sep 17 00:00:00 2001 From: Jim Warner Date: Fri, 10 Feb 2012 15:15:15 -0600 Subject: [PATCH] top: update latest CPU % distortions understanding We originally approached the potential problem of % CPU distortions as unique to Nehalem type cpus. The latest information suggests that it may have been due to a kernel anomaly that has since been corrected. Yet even without such a cpu, wide disparities in tics allocation among all available cpus have sometimes been observed -- spikes as it were in the normal pattern. This has happened under both version 2.26.38-13 and 3.0.0-15 kernels. The small amount of additional code addressing the original problem carries very little overhead. It is being retained to afford protection against any future tic accounting aberrations. In this commit, supporting programmer comments have been divorced from any particular cpu type. Also, another variable and manifest constant will now be eliminated when CPU_ZEROTICS is defined. References: commit 02508b3d76af5bc33c7e559b84d3e5e123cdf2ac http://www.freelists.org/post/procps/CStates-handling-new-switch,50 --- top/top.c | 11 +++++------ top/top.h | 10 +++++++--- 2 files changed, 12 insertions(+), 9 deletions(-) diff --git a/top/top.c b/top/top.c index 1d89711a..5d3db5f1 100644 --- a/top/top.c +++ b/top/top.c @@ -1836,14 +1836,13 @@ static CPU_t *cpus_refresh (CPU_t *cpus) { , &cpus[Cpu_faux_tot].cur.i, &cpus[Cpu_faux_tot].cur.w, &cpus[Cpu_faux_tot].cur.x , &cpus[Cpu_faux_tot].cur.y, &cpus[Cpu_faux_tot].cur.z)) error_exit(N_txt(FAIL_statget_txt)); +#ifndef CPU_ZEROTICS cpus[Cpu_faux_tot].cur.tot = cpus[Cpu_faux_tot].cur.u + cpus[Cpu_faux_tot].cur.s + cpus[Cpu_faux_tot].cur.n + cpus[Cpu_faux_tot].cur.i + cpus[Cpu_faux_tot].cur.w + cpus[Cpu_faux_tot].cur.x + cpus[Cpu_faux_tot].cur.y + cpus[Cpu_faux_tot].cur.z; -#ifndef CPU_ZEROTICS - /* if a Nehalem type cpu has been turned off completely, and thus registers - very few total tics, we'll force it to be treated as idle when that total - falls below a % of those expected -- other cpus will register their full - number of expected tics as 'idle' and thus won't be effected */ + /* if a cpu has registered substantially fewer tics than those expected, + we'll force it to be treated as 'idle' so as not to present misleading + percentages. */ cpus[Cpu_faux_tot].edge = ((cpus[Cpu_faux_tot].cur.tot - cpus[Cpu_faux_tot].sav.tot) / smp_num_cpus) / (100 / TICS_EDGE); #endif @@ -1866,9 +1865,9 @@ static CPU_t *cpus_refresh (CPU_t *cpus) { } #ifndef CPU_ZEROTICS cpus[i].edge = cpus[Cpu_faux_tot].edge; -#endif // this is for symmetry only, it's not currently required cpus[i].cur.tot = cpus[Cpu_faux_tot].cur.tot; +#endif #ifdef PRETEND4CPUS cpus[i].id = i; #endif diff --git a/top/top.h b/top/top.h index f3d234f8..fbb89a4b 100644 --- a/top/top.h +++ b/top/top.h @@ -62,9 +62,9 @@ for nls support inclusion. They're identified with: // nls_maybe */ - /* For initiating the topic of potential % CPU distortions due - to Nehalem type processors (see CPU_ZEROTICS), thanks to: - Jaromir Capik, - February, 2012 */ + /* For initiating the topic of potential % CPU distortions due to + to kernel and/or cpu anomalies (see CPU_ZEROTICS), thanks to: + Jaromir Capik, - February, 2012 */ #ifdef PRETEND2_5_X #define linux_version_code LINUX_VERSION(2,5,43) @@ -133,10 +133,12 @@ -- used at startup and for task/thread mode transitions */ #define PROC_XTRA -1 +#ifndef CPU_ZEROTICS /* This is the % used in establishing the tics threshold below which a cpu is treated as 'idle' rather than displaying misleading state percentages */ #define TICS_EDGE 20 +#endif /* ##### Enum's and Typedef's ############################################ */ @@ -223,7 +225,9 @@ typedef struct CT_t { 2.6.0 kernel: x == hi (hardware irq time), y == si (software irq time) 2.6.11 kernel: z == st (virtual steal time) */ TIC_t u, n, s, i, w, x, y, z; // as represented in /proc/stat +#ifndef CPU_ZEROTICS SIC_t tot; // total from /proc/stat line 1 +#endif } CT_t; typedef struct CPU_t {