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Neil Brown wrote:
>On Friday July 11, willy@debian.org wrote:
>
>># define do_div(n,base) ({ \
>> uint32_t __base = (base); \
>> uint32_t __rem; \
>> if (likely(((n) >> 32) == 0)) { \
>>
>>so if we call do_div() on a u32, the compiler emits nasal daemons.
>>and we do this -- in the antcipatory scheduler:
>>
>> if (aic->seek_samples) {
>> aic->seek_mean = aic->seek_total + 128;
>> do_div(aic->seek_mean, aic->seek_samples);
>> }
>>
>>seek_mean is a sector_t so sometimes it's 64-bit on a 32-bit platform.
>>so we can't avoid calling do_div().
>>
>>This almost works (the warning is harmless since gcc optimises away the call)
>>
>># define do_div(n,base) ({ \
>> uint32_t __base = (base); \
>> uint32_t __rem; \
>> if ((sizeof(n) < 8) || (likely(((n) >> 32) == 0))) { \
>> __rem = (uint32_t)(n) % __base; \
>> (n) = (uint32_t)(n) / __base; \
>> } else \
>> __rem = __div64_32(&(n), __base); \
>> __rem; \
>> })
>>
>>Better ideas?
>>
>
>sector_div, defined in blkdev.h, is probably what you want.
>
Looks right. Following patch alright?
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--- linux-2.5/drivers/block/as-iosched.c.orig 2003-07-12 10:12:20.000000000 +1000
+++ linux-2.5/drivers/block/as-iosched.c 2003-07-12 10:12:28.000000000 +1000
@@ -837,7 +837,7 @@ static void as_update_iohist(struct as_i
aic->seek_total += 256*seek_dist;
if (aic->seek_samples) {
aic->seek_mean = aic->seek_total + 128;
- do_div(aic->seek_mean, aic->seek_samples);
+ sector_div(aic->seek_mean, aic->seek_samples);
}
aic->seek_samples = (aic->seek_samples>>1)
+ (aic->seek_samples>>2);
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