| Message ID | 20230818095000.937633-1-liaochang1@huawei.com (mailing list archive) |
|---|---|
| State | Mainlined, archived |
| Headers | show |
| Series | cpufreq: stats: Improve the performance of cpufreq_stats_create_table() | expand |
On 18-08-23, 09:50, Liao Chang wrote: > In the worst case, the freq_table of policy data is not sorted and > contains duplicate frequencies, this means that it needs to iterate > through the entire freq_table of policy to ensure each frequency is > unique in the freq_table of stats data, this has a time complexity of > O(N^2), where N is the number of frequencies in the freq_table of > policy. > > However, if the policy.freq_table is already sorted and contains no > duplicate frequencices, it can reduce the time complexity of creating > stats.freq_table to O(N), the 'freq_table_sorted' field of policy data > can be used to indicate whether the policy.freq_table is sorted. > > Signed-off-by: Liao Chang <liaochang1@huawei.com> > --- > drivers/cpufreq/cpufreq_stats.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c > index 55c7ffd37d1c..fcb74050711a 100644 > --- a/drivers/cpufreq/cpufreq_stats.c > +++ b/drivers/cpufreq/cpufreq_stats.c > @@ -243,7 +243,8 @@ void cpufreq_stats_create_table(struct cpufreq_policy *policy) > > /* Find valid-unique entries */ > cpufreq_for_each_valid_entry(pos, policy->freq_table) > - if (freq_table_get_index(stats, pos->frequency) == -1) > + if ((policy->freq_table_sorted != CPUFREQ_TABLE_UNSORTED) || > + (freq_table_get_index(stats, pos->frequency) == -1)) > stats->freq_table[i++] = pos->frequency; > > stats->state_num = i; Acked-by: Viresh Kumar <viresh.kumar@linaro.org>
On Aug 18, 2023 at 09:50:00 +0000, Liao Chang wrote: > In the worst case, the freq_table of policy data is not sorted and > contains duplicate frequencies, this means that it needs to iterate > through the entire freq_table of policy to ensure each frequency is > unique in the freq_table of stats data, this has a time complexity of > O(N^2), where N is the number of frequencies in the freq_table of > policy. > > However, if the policy.freq_table is already sorted and contains no > duplicate frequencices, it can reduce the time complexity of creating s/frequencices/frequencies? > stats.freq_table to O(N), the 'freq_table_sorted' field of policy data > can be used to indicate whether the policy.freq_table is sorted. > > Signed-off-by: Liao Chang <liaochang1@huawei.com> > --- > drivers/cpufreq/cpufreq_stats.c | 3 ++- > 1 file changed, 2 insertions(+), 1 deletion(-) > > diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c > index 55c7ffd37d1c..fcb74050711a 100644 > --- a/drivers/cpufreq/cpufreq_stats.c > +++ b/drivers/cpufreq/cpufreq_stats.c > @@ -243,7 +243,8 @@ void cpufreq_stats_create_table(struct cpufreq_policy *policy) > > /* Find valid-unique entries */ > cpufreq_for_each_valid_entry(pos, policy->freq_table) > - if (freq_table_get_index(stats, pos->frequency) == -1) > + if ((policy->freq_table_sorted != CPUFREQ_TABLE_UNSORTED) || [...] Otherwise looks okay to me, Reviewed-by: Dhruva Gole <d-gole@ti.com>
On Mon, Aug 21, 2023 at 11:14 AM Dhruva Gole <d-gole@ti.com> wrote: > > On Aug 18, 2023 at 09:50:00 +0000, Liao Chang wrote: > > In the worst case, the freq_table of policy data is not sorted and > > contains duplicate frequencies, this means that it needs to iterate > > through the entire freq_table of policy to ensure each frequency is > > unique in the freq_table of stats data, this has a time complexity of > > O(N^2), where N is the number of frequencies in the freq_table of > > policy. > > > > However, if the policy.freq_table is already sorted and contains no > > duplicate frequencices, it can reduce the time complexity of creating > > s/frequencices/frequencies? I've fixed this when applying the patch. > > stats.freq_table to O(N), the 'freq_table_sorted' field of policy data > > can be used to indicate whether the policy.freq_table is sorted. > > > > Signed-off-by: Liao Chang <liaochang1@huawei.com> > > --- > > drivers/cpufreq/cpufreq_stats.c | 3 ++- > > 1 file changed, 2 insertions(+), 1 deletion(-) > > > > diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c > > index 55c7ffd37d1c..fcb74050711a 100644 > > --- a/drivers/cpufreq/cpufreq_stats.c > > +++ b/drivers/cpufreq/cpufreq_stats.c > > @@ -243,7 +243,8 @@ void cpufreq_stats_create_table(struct cpufreq_policy *policy) > > > > /* Find valid-unique entries */ > > cpufreq_for_each_valid_entry(pos, policy->freq_table) > > - if (freq_table_get_index(stats, pos->frequency) == -1) > > + if ((policy->freq_table_sorted != CPUFREQ_TABLE_UNSORTED) || I've also removed the redundant parens from this check. > > [...] > > Otherwise looks okay to me, > > Reviewed-by: Dhruva Gole <d-gole@ti.com> Applied as 6.6 material (with the changes mentioned above), thanks!
diff --git a/drivers/cpufreq/cpufreq_stats.c b/drivers/cpufreq/cpufreq_stats.c index 55c7ffd37d1c..fcb74050711a 100644 --- a/drivers/cpufreq/cpufreq_stats.c +++ b/drivers/cpufreq/cpufreq_stats.c @@ -243,7 +243,8 @@ void cpufreq_stats_create_table(struct cpufreq_policy *policy) /* Find valid-unique entries */ cpufreq_for_each_valid_entry(pos, policy->freq_table) - if (freq_table_get_index(stats, pos->frequency) == -1) + if ((policy->freq_table_sorted != CPUFREQ_TABLE_UNSORTED) || + (freq_table_get_index(stats, pos->frequency) == -1)) stats->freq_table[i++] = pos->frequency; stats->state_num = i;
In the worst case, the freq_table of policy data is not sorted and contains duplicate frequencies, this means that it needs to iterate through the entire freq_table of policy to ensure each frequency is unique in the freq_table of stats data, this has a time complexity of O(N^2), where N is the number of frequencies in the freq_table of policy. However, if the policy.freq_table is already sorted and contains no duplicate frequencices, it can reduce the time complexity of creating stats.freq_table to O(N), the 'freq_table_sorted' field of policy data can be used to indicate whether the policy.freq_table is sorted. Signed-off-by: Liao Chang <liaochang1@huawei.com> --- drivers/cpufreq/cpufreq_stats.c | 3 ++- 1 file changed, 2 insertions(+), 1 deletion(-)