Re: [PATCH v1] fuse: enable large folios

On 6/24/26 2:10 PM, Horst Birthelmer wrote:
> On Wed, Jun 24, 2026 at 12:34:16PM +0800, Jingbo Xu wrote:
>>
>>
>> On 6/24/26 9:21 AM, Joanne Koong wrote:
>>> Enable large folios, capping the max order at the largest request fuse
>>> can issue, so a folio always fits within a single request. The order
>>> range minimum is 0, so under memory pressure the allocator falls back to
>>> smaller folios.
>>>
>>> Benchmarks (libfuse passthrough_hp, buffered fio, single job, 4 GiB
>>> file, medians, NUMA-pinned, performance governor, strictlimiting on by
>>> default):
>>>
>>> tmpfs backing (page-cache bound):
>>>   workload          bs      large folios off   on        delta
>>>   seq read,  cold,  128k    3110 MiB/s    4514 MiB/s     +45%
>>>   seq read,  cold,  1M      3079 MiB/s    5181 MiB/s     +68%
>>>   seq read,  warm,  128k    2438 MiB/s    4486 MiB/s     +84%
>>>   seq read,  warm,  1M      2403 MiB/s    5123 MiB/s    +113%
>>>   writeback write, seq,128k 1211 MiB/s    1699 MiB/s     +40%
>>>   writeback write, seq, 1M  1462 MiB/s    2208 MiB/s     +51%
>>>   writeback write, rand,128k 1101 MiB/s   1757 MiB/s     +60% +
>>>   writeback write, rand, 1M 1284 MiB/s    2228 MiB/s     +74% +
>>>
>>> xfs on NVMe backing (device bound for cold I/O):
>>>   workload          bs      large folios off   on        delta
>>>   seq read,  cold,  128k    2030 MiB/s    2172 MiB/s      +7% *
>>>   seq read,  cold,  1M      1999 MiB/s    2181 MiB/s      +9% *
>>>   seq read,  warm,  128k    2451 MiB/s    4939 MiB/s    +101%
>>>   seq read,  warm,  1M      2340 MiB/s    5639 MiB/s    +141%
>>>   writeback write, seq,128k  637 MiB/s     747 MiB/s     +17% *
>>>   writeback write, seq, 1M   694 MiB/s     833 MiB/s     +20% *
>>>   writeback write, rand,128k 1004 MiB/s   1648 MiB/s     +64% +
>>>   writeback write, rand, 1M 1171 MiB/s    2055 MiB/s     +75% +
>>>
>>> (*) device-bandwidth bound. Not much throughput gain but system cpu
>>> utilization was roughly halved
>>> (+) random write was tested as an overwrite of a hot region (under
>>> writeback, this is page-cache bound, so the gain comes from lower
>>> per-folio cpu overhead rather than higher backing-device throughput)
>>>
>>> Random reads (4k and 128k) and writethrough writes were neutral with
>>> no regression (no read-modify-write or read-amplification penalty from
>>> large folios)
>>>
>>> More information about the benchmark setup and results are in
>>> https://github.com/joannekoong/linux/commits/fuse_large_folios_benchmarks/
>>>
>>> Signed-off-by: Joanne Koong <[email protected]>
>>> ---
>>> This has a dependency on the iomap uptodate helpers that were submitted to
>>> Christian's vfs tree [1]. If it's easier to route this patch through
>>> Christian's tree, I can resubmit this.
>>>
>>> [1] https://lore.kernel.org/linux-fsdevel/[email protected]/
>>>
>>>  fs/fuse/file.c | 10 ++++++++++
>>>  1 file changed, 10 insertions(+)
>>>
>>> diff --git a/fs/fuse/file.c b/fs/fuse/file.c
>>> index cb8da4c06d17..3c9be6d8ede1 100644
>>> --- a/fs/fuse/file.c
>>> +++ b/fs/fuse/file.c
>>> @@ -3136,4 +3136,14 @@ void fuse_init_file_inode(struct inode *inode, unsigned int flags)
>>>  
>>>  	if (IS_ENABLED(CONFIG_FUSE_DAX))
>>>  		fuse_dax_inode_init(inode, flags);
>>> +
>>> +	if (!FUSE_IS_DAX(inode)) {
>>> +		unsigned int max_pages = min(min(fc->max_write,
>>> +						 fc->max_read) >> PAGE_SHIFT,
>>> +					     fc->max_pages);
>>> +
>>> +		if (max_pages)
>>> +			mapping_set_folio_order_range(inode->i_mapping, 0,
>>> +						      ilog2(max_pages));
>>> +	}
>>>  }
>>
>> mapping_set_folio_order_range(..., 0, 0) seems harmless even when
>> max_pages is 0.
>>
>> Anyway
>>
>> Reviewed-by: Jingbo Xu \<[email protected]\>
>>
> 
> I was just about to suggest something like
> 
> mapping_set_folio_order_range(inode->i_mapping, 0,
> 			      ilog2(max_pages ?: 1));
> 
> but you are right, it's not a problem.
>>
>> -- 
>> Thanks,
>> Jingbo
>>
> 
> This was actually one of the problems I ran into when I enabled large folios in linux 6.17.
> Since it would create problems for readahead.
> 
> Reviewed-By: Horst Birthelmer <[email protected]>
> 

Okay I got it.  ilog2(0) doesn't equal to 0


-- 
Thanks,
Jingbo