>>> @@ -402,9 +403,16 @@ int sg_alloc_table_from_pages(struct sg_table *sgt,
>>>
>>> /* compute number of contiguous chunks */
>>> chunks = 1;
>>> - for (i = 1; i < n_pages; ++i)
>>> - if (page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) +
>>> 1)
>>> + seg_len = PAGE_SIZE;
>>> + for (i = 1; i < n_pages; ++i) {
>>> + if (seg_len >= max_segment ||
>>> + page_to_pfn(pages[i]) != page_to_pfn(pages[i - 1]) +
>>> 1) {
>>> ++chunks;
>>> + seg_len = PAGE_SIZE;
>>> + } else {
>>> + seg_len += PAGE_SIZE;
>>> + }
>>> + }
>>
>>
>> Wouldn't be following looks more readable?
>>
>> seg_len = 0;
>> // Are compilers so stupid doing calculation per iteration in
>> for-conditional?
>> // for (i = 0; i + 1 < n_pages; i++) ?
>
>
> I didn't get what you meant here?
Why do we start from 1? I see here two micro (?) optimizations:
1) starting from 1 on believe that compiler dumb enough to every time
do a calculation in condition;
2) ++i instead of i++, but this is just matter of style, it's not a c++.
>> for (i = 1; i < n_pages; ++i) {
>> seg_len += PAGE_SIZE;
>> if (seg_len >= max_segment || page_to_pfn(pages[i]) !=
>> page_to_pfn(pages[i - 1]) + 1) {
>> ++chunks;
>> seg_len = PAGE_SIZE;
>> }
>> }
>
>
> Tried it in my unit tester but it doesn't work for all scenarios, guess
> there is a subtle bug somewhere. I don't find it that unreadable so would
> prefer to leave it since it works.
Last seems has to be
seg_len = 0;
--
With Best Regards,
Andy Shevchenko
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