Eric Lee / smarc-ti-linux-kernel

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Commit e8ced39d5e8911c662d4d69a342b9d053eaaac4e

Authored by Mingming Cao
Committed by Theodore Ts'o
1 parent 64769240bd
Exists in master and in 20 other branches dlt-processor-sdk-linux-03.00.00.04, newt-ti-linux-3.12.y, processor-sdk-linux-01.00.00, processor-sdk-linux-02.00.01, smarc-ti-linux-3.12.10, smarc-ti-linux-3.12.y, smarc-ti-linux-3.14.y, smarc-ti-linux-3.15.y, smarc-ti-lsk-linux-4.1.y, smarct3x-processor-sdk-04.01.00.06, smarct3x-processor-sdk-linux-02.00.01, smarct3x-processor-sdk-linux-03.00.00.04, smarct4x-800-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-04.01.00.06, smarct4x-processor-sdk-linux-02.00.01, smarct4x-processor-sdk-linux-03.00.00.04, ti-linux-3.12.y, ti-linux-3.14.y, ti-linux-3.15.y, ti-lsk-linux-4.1.y

percpu_counter: new function percpu_counter_sum_and_set 

Delayed allocation need to check free blocks at every write time.
percpu_counter_read_positive() is not quit accurate. delayed
allocation need a more accurate accounting, but using
percpu_counter_sum_positive() is frequently is quite expensive.

This patch added a new function to update center counter when sum
per-cpu counter, to increase the accurate rate for next
percpu_counter_read() and require less calling expensive
percpu_counter_sum().

Signed-off-by: Mingming Cao <cmm@us.ibm.com>
Signed-off-by: "Theodore Ts'o" <tytso@mit.edu>

Showing 3 changed files with 16 additions and 5 deletions Side-by-side Diff

... ... @@ -1621,7 +1621,7 @@
1621 1621 #ifdef CONFIG_SMP
1622 1622 if (free_blocks - root_blocks < FBC_BATCH)
1623 1623 free_blocks =
1624   - percpu_counter_sum_positive(&sbi->s_freeblocks_counter);
  1624 + percpu_counter_sum_and_set(&sbi->s_freeblocks_counter);
1625 1625 #endif
1626 1626 if (free_blocks - root_blocks < nblocks)
1627 1627 return free_blocks - root_blocks;
include/linux/percpu_counter.h
Diff comments   View file @ e8ced39
... ... @@ -35,7 +35,7 @@
35 35 void percpu_counter_destroy(struct percpu_counter *fbc);
36 36 void percpu_counter_set(struct percpu_counter *fbc, s64 amount);
37 37 void __percpu_counter_add(struct percpu_counter *fbc, s64 amount, s32 batch);
38   -s64 __percpu_counter_sum(struct percpu_counter *fbc);
  38 +s64 __percpu_counter_sum(struct percpu_counter *fbc, int set);
39 39  
40 40 static inline void percpu_counter_add(struct percpu_counter *fbc, s64 amount)
41 41 {
42 42  
43 43  
... ... @@ -44,13 +44,19 @@
44 44  
45 45 static inline s64 percpu_counter_sum_positive(struct percpu_counter *fbc)
46 46 {
47   - s64 ret = __percpu_counter_sum(fbc);
  47 + s64 ret = __percpu_counter_sum(fbc, 0);
48 48 return ret < 0 ? 0 : ret;
49 49 }
50 50  
  51 +static inline s64 percpu_counter_sum_and_set(struct percpu_counter *fbc)
  52 +{
  53 + return __percpu_counter_sum(fbc, 1);
  54 +}
  55 +
  56 +
51 57 static inline s64 percpu_counter_sum(struct percpu_counter *fbc)
52 58 {
53   - return __percpu_counter_sum(fbc);
  59 + return __percpu_counter_sum(fbc, 0);
54 60 }
55 61  
56 62 static inline s64 percpu_counter_read(struct percpu_counter *fbc)
lib/percpu_counter.c
Diff comments   View file @ e8ced39
... ... @@ -52,7 +52,7 @@
52 52 * Add up all the per-cpu counts, return the result. This is a more accurate
53 53 * but much slower version of percpu_counter_read_positive()
54 54 */
55   -s64 __percpu_counter_sum(struct percpu_counter *fbc)
  55 +s64 __percpu_counter_sum(struct percpu_counter *fbc, int set)
56 56 {
57 57 s64 ret;
58 58 int cpu;
59 59  
... ... @@ -62,7 +62,12 @@
62 62 for_each_online_cpu(cpu) {
63 63 s32 *pcount = per_cpu_ptr(fbc->counters, cpu);
64 64 ret += *pcount;
  65 + if (set)
  66 + *pcount = 0;
65 67 }
  68 + if (set)
  69 + fbc->count = ret;
  70 +
66 71 spin_unlock(&fbc->lock);
67 72 return ret;
68 73 }