wb_update_write_bandwidth

Name:wb_update_write_bandwidth

Proto:static void wb_update_write_bandwidth(struct bdi_writeback *wb, unsigned long elapsed, unsigned long written)

Type:void

Parameter:

Type	Parameter	Name
struct bdi_writeback *	wb
unsigned long	elapsed
unsigned long	written

1087

period = undup_pow_of_two - round the given value up to nearest power of two*@n: parameter* round the given value up to the nearest power of two* - the result is undefined when n == 0* - this can be used to initialise global variables from constant data(3 * HZ)

1088

avg = urther smoothed write bw, > 0

1089

old = he estimated write bandwidth

1102

bw = written - min - return minimum of two values of the same or compatible types*@x: first value*@y: second value(written, pages written at bw_time_stamp )

1103

bw *= HZ

1104

If Value for the false possibility is greater at compile time(elapsed > period) Then

1105

bw = div64_ul(bw, elapsed)

1106

avg = bw

1107

Go to out

1109

bw += he estimated write bandwidth * (period - elapsed)

1110

bw >>= log2 - log base 2 of 32-bit or a 64-bit unsigned value*@n: parameter* constant-capable log of base 2 calculation* - this can be used to initialise global variables from constant data, hence* the massive ternary operator construction* selects the (period)

1115

If avg > old && old >= bw Then avg -= avg - old >> 3

1118

If avg < old && old <= bw Then avg += old - avg >> 3

1121

out :

1123

avg = max - return maximum of two values of the same or compatible types*@x: first value*@y: second value(avg, 1LU)

1124

If wb_has_dirty_io(wb) Then

1125

delta = avg - urther smoothed write bw, > 0

1126

WARN_ON_ONCE(atomic_long_add_return(delta, & tot_write_bandwidth) <= 0)

1129

he estimated write bandwidth = bw

1130

urther smoothed write bw, > 0 = avg

**Caller**
Name	Describe
__wb_update_bandwidth

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