svn commit: r267364 - head/sys/vm

[Alan Cox]

On 06/12/2014 18:46, Adrian Chadd wrote:
> Hi!
>
> Wouldn't this also be fixed if popmap_t was a unsigned char (to match
> what setbit/clrbit/etc do) and then use the existing macros?
>
> Is there any reason popmap_t is not a uchar ? Is it ever accessed as
> anything other than an array of chars?

Yes, there is.  Parts of the code that you don't see in the below change
make heavy use of ffsl() on the population map.

>
>
> On 11 June 2014 11:11, Alan Cox <alc at freebsd.org> wrote:
>> Author: alc
>> Date: Wed Jun 11 16:11:12 2014
>> New Revision: 267364
>> URL: http://svnweb.freebsd.org/changeset/base/267364
>>
>> Log:
>>   Correct a bug in the management of the population map on big-endian
>>   machines.  Specifically, there was a mismatch between how the routine
>>   allocation and deallocation operations accessed the population map
>>   and how the aggressively optimized reservation-breaking operation
>>   accessed it.  So, problems only occurred when reservations were broken.
>>   This change makes the routine operations access the population map in
>>   the same way as the reservation breaking operation.
>>
>>   This bug was introduced in r259999.
>>
>>   PR:           187080
>>   Tested by:    jmg (on an "armeb" machine)
>>   Sponsored by: EMC / Isilon Storage Division
>>
>> Modified:
>>   head/sys/vm/vm_reserv.c
>>
>> Modified: head/sys/vm/vm_reserv.c
>> ==============================================================================
>> --- head/sys/vm/vm_reserv.c     Wed Jun 11 14:53:58 2014        (r267363)
>> +++ head/sys/vm/vm_reserv.c     Wed Jun 11 16:11:12 2014        (r267364)
>> @@ -108,6 +108,46 @@ typedef    u_long          popmap_t;
>>  #define        NPOPMAP         howmany(VM_LEVEL_0_NPAGES, NBPOPMAP)
>>
>>  /*
>> + * Clear a bit in the population map.
>> + */
>> +static __inline void
>> +popmap_clear(popmap_t popmap[], int i)
>> +{
>> +
>> +       popmap[i / NBPOPMAP] &= ~(1UL << (i % NBPOPMAP));
>> +}
>> +
>> +/*
>> + * Set a bit in the population map.
>> + */
>> +static __inline void
>> +popmap_set(popmap_t popmap[], int i)
>> +{
>> +
>> +       popmap[i / NBPOPMAP] |= 1UL << (i % NBPOPMAP);
>> +}
>> +
>> +/*
>> + * Is a bit in the population map clear?
>> + */
>> +static __inline boolean_t
>> +popmap_is_clear(popmap_t popmap[], int i)
>> +{
>> +
>> +       return ((popmap[i / NBPOPMAP] & (1UL << (i % NBPOPMAP))) == 0);
>> +}
>> +
>> +/*
>> + * Is a bit in the population map set?
>> + */
>> +static __inline boolean_t
>> +popmap_is_set(popmap_t popmap[], int i)
>> +{
>> +
>> +       return ((popmap[i / NBPOPMAP] & (1UL << (i % NBPOPMAP))) != 0);
>> +}
>> +
>> +/*
>>   * The reservation structure
>>   *
>>   * A reservation structure is constructed whenever a large physical page is
>> @@ -241,7 +281,7 @@ vm_reserv_depopulate(vm_reserv_t rv, int
>>         mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
>>         KASSERT(rv->object != NULL,
>>             ("vm_reserv_depopulate: reserv %p is free", rv));
>> -       KASSERT(isset(rv->popmap, index),
>> +       KASSERT(popmap_is_set(rv->popmap, index),
>>             ("vm_reserv_depopulate: reserv %p's popmap[%d] is clear", rv,
>>             index));
>>         KASSERT(rv->popcnt > 0,
>> @@ -255,7 +295,7 @@ vm_reserv_depopulate(vm_reserv_t rv, int
>>                     rv));
>>                 rv->pages->psind = 0;
>>         }
>> -       clrbit(rv->popmap, index);
>> +       popmap_clear(rv->popmap, index);
>>         rv->popcnt--;
>>         if (rv->popcnt == 0) {
>>                 LIST_REMOVE(rv, objq);
>> @@ -302,7 +342,7 @@ vm_reserv_populate(vm_reserv_t rv, int i
>>         mtx_assert(&vm_page_queue_free_mtx, MA_OWNED);
>>         KASSERT(rv->object != NULL,
>>             ("vm_reserv_populate: reserv %p is free", rv));
>> -       KASSERT(isclr(rv->popmap, index),
>> +       KASSERT(popmap_is_clear(rv->popmap, index),
>>             ("vm_reserv_populate: reserv %p's popmap[%d] is set", rv,
>>             index));
>>         KASSERT(rv->popcnt < VM_LEVEL_0_NPAGES,
>> @@ -313,7 +353,7 @@ vm_reserv_populate(vm_reserv_t rv, int i
>>                 TAILQ_REMOVE(&vm_rvq_partpop, rv, partpopq);
>>                 rv->inpartpopq = FALSE;
>>         }
>> -       setbit(rv->popmap, index);
>> +       popmap_set(rv->popmap, index);
>>         rv->popcnt++;
>>         if (rv->popcnt < VM_LEVEL_0_NPAGES) {
>>                 rv->inpartpopq = TRUE;
>> @@ -503,7 +543,7 @@ found:
>>                 return (NULL);
>>         /* Handle vm_page_rename(m, new_object, ...). */
>>         for (i = 0; i < npages; i++)
>> -               if (isset(rv->popmap, index + i))
>> +               if (popmap_is_set(rv->popmap, index + i))
>>                         return (NULL);
>>         for (i = 0; i < npages; i++)
>>                 vm_reserv_populate(rv, index + i);
>> @@ -628,7 +668,7 @@ found:
>>         index = VM_RESERV_INDEX(object, pindex);
>>         m = &rv->pages[index];
>>         /* Handle vm_page_rename(m, new_object, ...). */
>> -       if (isset(rv->popmap, index))
>> +       if (popmap_is_set(rv->popmap, index))
>>                 return (NULL);
>>         vm_reserv_populate(rv, index);
>>         return (m);
>> @@ -662,9 +702,9 @@ vm_reserv_break(vm_reserv_t rv, vm_page_
>>                  * to the physical memory allocator.
>>                  */
>>                 i = m - rv->pages;
>> -               KASSERT(isclr(rv->popmap, i),
>> +               KASSERT(popmap_is_clear(rv->popmap, i),
>>                     ("vm_reserv_break: reserv %p's popmap is corrupted", rv));
>> -               setbit(rv->popmap, i);
>> +               popmap_set(rv->popmap, i);
>>                 rv->popcnt++;
>>         }
>>         i = hi = 0;
>>
>