Re: [PATCH 2/2] xfs: count folio alloc'd xfs_buf items in NR_KERNEL_MISC_RECLAIMABLE

On 8/14/26 2:25 AM, Christoph Hellwig wrote:
> On Thu, Aug 13, 2026 at 03:40:53PM -0500, Eric Sandeen wrote:
>> xfs_buf allocations via xfs_buf_alloc_folio are actually reclaimable,
>> but are not accounted for as such. NR_KERNEL_MISC_RECLAIMABLE seems
>> made for this purpose, although AFAICT there are no users today.
>>
>> To achieve this, add a new flag _XBF_PAGES to track what we have
>> allocated this way, increment the NR_KERNEL_MISC_RECLAIMABLE
>> count when we do, and then do the reverse when they are freed.
> 
> I don't see why we'd need the flag.  All buffers are either allocated
> using vmalloc, kmalloc or as folios.  So it should always be set for
> folio allocations (and is misnamed since it now covers folios as well).

Hmm ok I think you're right. And using PAGES is misnamed, yeah.
>>
>> These allocations now show up under nr_kernel_misc_reclaimable in
>> /proc/vmstat when allocations are active, which in turn makes
>> MemAvailable more accurate in /proc/meminfo.
> 
> Adding linux-mm and a few people that touched this counter for
> opinions.  I guess the counter is only for full folios, and we
> should not set it for the small than page kmalloc allocations?
> But even with that, why not set it for the vmalloc allocations?
I hesitated based on node accounting but dchinner sounded unconcerned:
"If it gets accounted to the node of the first folio,
then it will at least always be consistently accounted, if not
always 100% accurate for the vmalloc case."

I fixed those up but won't resend just yet, thanks.

And I promise to use more columns next time ;)

-Eric