Re: [PATCH 0/3] Create large folios in iomap buffered write path

[Matthew Wilcox <willy@infradead.org>]

On Sun, May 21, 2023 at 08:49:53AM +0800, Wang Yugui wrote:
> Hi,
> 
> > Wang Yugui has a workload which would be improved by using large folios.
> > Until now, we've only created large folios in the readahead path,
> > but this workload writes without reading.  The decision of what size
> > folio to create is based purely on the size of the write() call (unlike
> > readahead where we keep history and can choose to create larger folios
> > based on that history even if individual reads are small).
> > 
> > The third patch looks like it's an optional extra but is actually needed
> > for the first two patches to work in the write path, otherwise it limits
> > the length that iomap_get_folio() sees to PAGE_SIZE.
> 
> very good test result on 6.4.0-rc2. 
> # just drop ';' in 'if (bytes > folio_size(folio) - offset);' of [PATCH 3/3].
> 
> fio -name write-bandwidth -rw=write -bs=1024Ki -size=32Gi -runtime=30 -iodepth 1
> -ioengine sync -zero_buffers=1 -direct=0 -end_fsync=1 -numjobs=4
> -directory=/mnt/test
> fio WRITE: bw=7655MiB/s (8027MB/s).
> 
> Now it is the same as 5.15.y

Great!  How close is that to saturating the theoretical write bandwidth
of your storage?