On Fri, Aug 15, 2025 at 4:01 AM Jingbo Xu <jefflexu@xxxxxxxxxxxxxxxxx> wrote:
>
>
>
> On 8/12/25 4:40 AM, Joanne Koong wrote:
> > Large folios are only enabled if the writeback cache isn't on.
> > (Strictlimiting needs to be turned off if the writeback cache is used in
> > conjunction with large folios, else this tanks performance.)
> >
> > Benchmarks showed noticeable improvements for writes (both sequential
> > and random). There were no performance differences seen for random reads
> > or direct IO. For sequential reads, there was no performance difference
> > seen for the first read (which populates the page cache) but subsequent
> > sequential reads showed a huge speedup.
> >
> > Benchmarks were run using fio on the passthrough_hp fuse server:
> > ~/libfuse/build/example/passthrough_hp ~/libfuse ~/fuse_mnt --nopassthrough --nocache
> >
> > run fio in ~/fuse_mnt:
> > fio --name=test --ioengine=sync --rw=write --bs=1M --size=5G --numjobs=2 --ramp_time=30 --group_reporting=1
> >
> > Results (tested on bs=256K, 1M, 5M) showed roughly a 15-20% increase in
> > write throughput and for sequential reads after the page cache has
> > already been populated, there was a ~800% speedup seen.
> >
> > Signed-off-by: Joanne Koong <joannelkoong@xxxxxxxxx>
> > ---
> > fs/fuse/file.c | 18 ++++++++++++++++--
> > 1 file changed, 16 insertions(+), 2 deletions(-)
> >
> > diff --git a/fs/fuse/file.c b/fs/fuse/file.c
> > index adc4aa6810f5..2e7aae294c9e 100644
> > --- a/fs/fuse/file.c
> > +++ b/fs/fuse/file.c
> > @@ -1167,9 +1167,10 @@ static ssize_t fuse_fill_write_pages(struct fuse_io_args *ia,
> > pgoff_t index = pos >> PAGE_SHIFT;
> > unsigned int bytes;
> > unsigned int folio_offset;
> > + fgf_t fgp = FGP_WRITEBEGIN | fgf_set_order(num);
> >
> > again:
> > - folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
> > + folio = __filemap_get_folio(mapping, index, fgp,
> > mapping_gfp_mask(mapping));
> > if (IS_ERR(folio)) {
> > err = PTR_ERR(folio);
> > @@ -3155,11 +3156,24 @@ void fuse_init_file_inode(struct inode *inode, unsigned int flags)
> > {
> > struct fuse_inode *fi = get_fuse_inode(inode);
> > struct fuse_conn *fc = get_fuse_conn(inode);
> > + unsigned int max_pages, max_order;
> >
> > inode->i_fop = &fuse_file_operations;
> > inode->i_data.a_ops = &fuse_file_aops;
> > - if (fc->writeback_cache)
> > + if (fc->writeback_cache) {
> > mapping_set_writeback_may_deadlock_on_reclaim(&inode->i_data);
> > + } else {
> > + /*
> > + * Large folios are only enabled if the writeback cache isn't on.
> > + * If the writeback cache is on, large folios should only be
> > + * enabled in conjunction with strictlimiting turned off, else
> > + * performance tanks.
> > + */
> > + max_pages = min(min(fc->max_write, fc->max_read) >> PAGE_SHIFT,
> > + fc->max_pages);
> > + max_order = ilog2(max_pages);
> > + mapping_set_folio_order_range(inode->i_mapping, 0, max_order);
> > + }
>
> JFYI fc->max_read shall also be honored when calculating max_order,
> otherwise the following warning in fuse_readahead() may be triggered.
>
Hi Jingbo,
I think fc->max_read gets honored in the "min(fc->max_write,
fc->max_read)" part of the max_pages calculation above.
Thanks,
Joanne
> /*
> * Large folios belonging to fuse will never
> * have more pages than max_pages.
> */
> WARN_ON(!pages);
>
>
> --
> Thanks,
> Jingbo
>
