diff options
Diffstat (limited to 'meta/recipes-kernel/linux/linux-netbook-2.6.33.2/linux-2.6.34-ondemand-fix-7-7.patch')
| -rw-r--r-- | meta/recipes-kernel/linux/linux-netbook-2.6.33.2/linux-2.6.34-ondemand-fix-7-7.patch | 114 |
1 files changed, 114 insertions, 0 deletions
diff --git a/meta/recipes-kernel/linux/linux-netbook-2.6.33.2/linux-2.6.34-ondemand-fix-7-7.patch b/meta/recipes-kernel/linux/linux-netbook-2.6.33.2/linux-2.6.34-ondemand-fix-7-7.patch new file mode 100644 index 000000000..32a2bdbb5 --- /dev/null +++ b/meta/recipes-kernel/linux/linux-netbook-2.6.33.2/linux-2.6.34-ondemand-fix-7-7.patch @@ -0,0 +1,114 @@ +>From 27966bedabea83c4f3ae77507eceb746b1f6ebae Mon Sep 17 00:00:00 2001 +From: Arjan van de Ven <arjan@linux.intel.com> +Date: Sun, 18 Apr 2010 11:15:56 -0700 +Subject: [PATCH 7/7] ondemand: Solve the big performance issue with ondemand during disk IO +Patch-mainline: in -mm tree as of 19 Apr 2010 + +The ondemand cpufreq governor uses CPU busy time (e.g. not-idle time) as +a measure for scaling the CPU frequency up or down. +If the CPU is busy, the CPU frequency scales up, if it's idle, the CPU +frequency scales down. Effectively, it uses the CPU busy time as proxy +variable for the more nebulous "how critical is performance right now" +question. + +This algorithm falls flat on its face in the light of workloads where +you're alternatingly disk and CPU bound, such as the ever popular +"git grep", but also things like startup of programs and maildir using +email clients... much to the chagarin of Andrew Morton. + +This patch changes the ondemand algorithm to count iowait time as busy, +not idle, time. As shown in the breakdown cases above, iowait is performance +critical often, and by counting iowait, the proxy variable becomes a more +accurate representation of the "how critical is performance" question. + +The problem and fix are both verified with the "perf timechar" tool. + +Signed-off-by: Arjan van de Ven <arjan@linux.intel.com> +--- + drivers/cpufreq/cpufreq_ondemand.c | 30 ++++++++++++++++++++++++++++-- + 1 files changed, 28 insertions(+), 2 deletions(-) + +diff --git a/drivers/cpufreq/cpufreq_ondemand.c b/drivers/cpufreq/cpufreq_ondemand.c +index bd444dc..ed472f8 100644 +--- a/drivers/cpufreq/cpufreq_ondemand.c ++++ b/drivers/cpufreq/cpufreq_ondemand.c +@@ -73,6 +73,7 @@ enum {DBS_NORMAL_SAMPLE, DBS_SUB_SAMPLE}; + + struct cpu_dbs_info_s { + cputime64_t prev_cpu_idle; ++ cputime64_t prev_cpu_iowait; + cputime64_t prev_cpu_wall; + cputime64_t prev_cpu_nice; + struct cpufreq_policy *cur_policy; +@@ -148,6 +149,16 @@ static inline cputime64_t get_cpu_idle_time(unsigned int cpu, cputime64_t *wall) + return idle_time; + } + ++static inline cputime64_t get_cpu_iowait_time(unsigned int cpu, cputime64_t *wall) ++{ ++ u64 iowait_time = get_cpu_iowait_time_us(cpu, wall); ++ ++ if (iowait_time == -1ULL) ++ return 0; ++ ++ return iowait_time; ++} ++ + /* + * Find right freq to be set now with powersave_bias on. + * Returns the freq_hi to be used right now and will set freq_hi_jiffies, +@@ -470,14 +481,15 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info) + + for_each_cpu(j, policy->cpus) { + struct cpu_dbs_info_s *j_dbs_info; +- cputime64_t cur_wall_time, cur_idle_time; +- unsigned int idle_time, wall_time; ++ cputime64_t cur_wall_time, cur_idle_time, cur_iowait_time; ++ unsigned int idle_time, wall_time, iowait_time; + unsigned int load, load_freq; + int freq_avg; + + j_dbs_info = &per_cpu(od_cpu_dbs_info, j); + + cur_idle_time = get_cpu_idle_time(j, &cur_wall_time); ++ cur_iowait_time = get_cpu_iowait_time(j, &cur_wall_time); + + wall_time = (unsigned int) cputime64_sub(cur_wall_time, + j_dbs_info->prev_cpu_wall); +@@ -487,6 +499,10 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info) + j_dbs_info->prev_cpu_idle); + j_dbs_info->prev_cpu_idle = cur_idle_time; + ++ iowait_time = (unsigned int) cputime64_sub(cur_iowait_time, ++ j_dbs_info->prev_cpu_iowait); ++ j_dbs_info->prev_cpu_iowait = cur_iowait_time; ++ + if (dbs_tuners_ins.ignore_nice) { + cputime64_t cur_nice; + unsigned long cur_nice_jiffies; +@@ -504,6 +520,16 @@ static void dbs_check_cpu(struct cpu_dbs_info_s *this_dbs_info) + idle_time += jiffies_to_usecs(cur_nice_jiffies); + } + ++ /* ++ * For the purpose of ondemand, waiting for disk IO is an ++ * indication that you're performance critical, and not that ++ * the system is actually idle. So subtract the iowait time ++ * from the cpu idle time. ++ */ ++ ++ if (idle_time >= iowait_time) ++ idle_time -= iowait_time; ++ + if (unlikely(!wall_time || wall_time < idle_time)) + continue; + +-- +1.6.2.5 + +-- +To unsubscribe from this list: send the line "unsubscribe linux-kernel" in +the body of a message to majordomo@vger.kernel.org +More majordomo info at http://vger.kernel.org/majordomo-info.html +Please read the FAQ at http://www.tux.org/lkml/ + |