Re: [PATCH v2 00/12] fuse: support large folios

Jingbo Xu
2024-12-06T09:50:33Z

Hi Joanne,

Have no checked the whole series yet, but I just spent some time on the
testing, attempting to find some statistics on the performance improvement.

At least we need:

@@ -2212,7 +2213,7 @@ static int fuse_write_begin(struct file *file,
struct address_space *mapping,

WARN_ON(!fc->writeback_cache);

- folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN,
+ folio = __filemap_get_folio(mapping, index, FGP_WRITEBEGIN |
fgf_set_order(len),

Otherwise the large folio is not enabled on the buffer write path.

Besides, when applying the above diff, the large folio is indeed enabled
but it suffers severe performance regression:

fio 1 job buffer write:
2GB/s BW w/o large folio, and 200MB/s BW w/ large folio

Have not figured it out yet.

On 11/26/24 6:05 AM, Joanne Koong wrote:
> This patchset adds support for folios larger than one page size in FUSE.
>
> This patchset is rebased on top of the (unmerged) patchset that removes temp
> folios in writeback [1]. (There is also a version of this patchset that is
> independent from that change, but that version has two additional patches
> needed to account for temp folios and temp folio copying, which may require
> some debate to get the API right for as these two patches add generic
> (non-FUSE) helpers. For simplicity's sake for now, I sent out this patchset
> version rebased on top of the patchset that removes temp pages)
>
> This patchset was tested by running it through fstests on passthrough_hp.
>
> Benchmarks show roughly a ~45% improvement in read throughput.
>
> Benchmark setup:
>
> -- Set up server --
> ./libfuse/build/example/passthrough_hp --bypass-rw=1 ~/libfuse
> ~/mounts/fuse/ --nopassthrough
> (using libfuse patched with https://github.com/libfuse/libfuse/pull/807)
>
> -- Run fio --
> fio --name=read --ioengine=sync --rw=read --bs=1M --size=1G
> --numjobs=2 --ramp_time=30 --group_reporting=1
> --directory=mounts/fuse/
>
> Machine 1:
> No large folios: ~4400 MiB/s
> Large folios: ~7100 MiB/s
>
> Machine 2:
> No large folios: ~3700 MiB/s
> Large folios: ~6400 MiB/s
>
> Writes are still effectively one page size. Benchmarks showed that trying to get
> the largest folios possible from __filemap_get_folio() is an over-optimization
> and ends up being significantly more expensive. Fine-tuning for the optimal
> order size for the __filemap_get_folio() calls can be done in a future patchset.
>
> [1] https://lore.kernel.org/linux-fsdevel/20241107235614.3637221-1-joannelkoong@gmail.com/
>
> Changelog:
> v1: https://lore.kernel.org/linux-fsdevel/20241109001258.2216604-1-joannelkoong@gmail.com/
> v1 -> v2:
> * Change naming from "non-writeback write" to "writethrough write"
> * Fix deadlock for writethrough writes by calling fault_in_iov_iter_readable() first
> before __filemap_get_folio() (Josef)
> * For readahead, retain original folio_size() for descs.length (Josef)
> * Use folio_zero_range() api in fuse_copy_folio() (Josef)
> * Add Josef's reviewed-bys
>
> Joanne Koong (12):
> fuse: support copying large folios
> fuse: support large folios for retrieves
> fuse: refactor fuse_fill_write_pages()
> fuse: support large folios for writethrough writes
> fuse: support large folios for folio reads
> fuse: support large folios for symlinks
> fuse: support large folios for stores
> fuse: support large folios for queued writes
> fuse: support large folios for readahead
> fuse: support large folios for direct io
> fuse: support large folios for writeback
> fuse: enable large folios
>
> fs/fuse/dev.c | 128 ++++++++++++++++++++++++-------------------------
> fs/fuse/dir.c | 8 ++--
> fs/fuse/file.c | 126 +++++++++++++++++++++++++++++++-----------------
> 3 files changed, 149 insertions(+), 113 deletions(-)
>

--
Thanks,
Jingbo