lkml.org 
[lkml]   [2018]   [Nov]   [12]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
/
SubjectRe: [mm PATCH v5 7/7] mm: Use common iterator for deferred_init_pages and deferred_free_pages
From
Date
On 11/9/2018 8:13 PM, Pavel Tatashin wrote:
> On 18-11-05 13:20:01, Alexander Duyck wrote:
>> +static unsigned long __next_pfn_valid_range(unsigned long *i,
>> + unsigned long end_pfn)
>> {
>> - if (!pfn_valid_within(pfn))
>> - return false;
>> - if (!(pfn & (pageblock_nr_pages - 1)) && !pfn_valid(pfn))
>> - return false;
>> - return true;
>> + unsigned long pfn = *i;
>> + unsigned long count;
>> +
>> + while (pfn < end_pfn) {
>> + unsigned long t = ALIGN(pfn + 1, pageblock_nr_pages);
>> + unsigned long pageblock_pfn = min(t, end_pfn);
>> +
>> +#ifndef CONFIG_HOLES_IN_ZONE
>> + count = pageblock_pfn - pfn;
>> + pfn = pageblock_pfn;
>> + if (!pfn_valid(pfn))
>> + continue;
>> +#else
>> + for (count = 0; pfn < pageblock_pfn; pfn++) {
>> + if (pfn_valid_within(pfn)) {
>> + count++;
>> + continue;
>> + }
>> +
>> + if (count)
>> + break;
>> + }
>> +
>> + if (!count)
>> + continue;
>> +#endif
>> + *i = pfn;
>> + return count;
>> + }
>> +
>> + return 0;
>> }
>>
>> +#define for_each_deferred_pfn_valid_range(i, start_pfn, end_pfn, pfn, count) \
>> + for (i = (start_pfn), \
>> + count = __next_pfn_valid_range(&i, (end_pfn)); \
>> + count && ({ pfn = i - count; 1; }); \
>> + count = __next_pfn_valid_range(&i, (end_pfn)))
>
> Can this be improved somehow? It took me a while to understand this
> piece of code. i is actually end of block, and not an index by PFN, ({pfn = i - count; 1;}) is
> simply hard to parse. Why can't we make __next_pfn_valid_range() to
> return both end and a start of a block?

One thing I could do is flip the direction and work from the end to the
start. If I did that then 'i' and 'pfn' would be the same value and I
wouldn't have to do the subtraction. If that works for you I could
probably do that and it may actually be more efficient.

Otherwise I could probably pass pfn as a reference, and compute it in
the case where count is non-zero.

> The rest is good:
>
> Reviewed-by: Pavel Tatashin <pasha.tatashin@soleen.com>
>
> Thank you,
> Pasha
>

\
 
 \ /
  Last update: 2018-11-12 16:12    [W:0.066 / U:0.240 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site