RE: [PATCH] exfat: improve performance of exfat_free_cluster when using dirsync mount option

["Namjae Jeon" <namjae.jeon@samsung.com>]

> > There are stressful update of cluster allocation bitmap when using
> > dirsync mount option which is doing sync buffer on every cluster bit clearing.
> > This could result in performance degradation when deleting big size file.
> > Fix to update only when the bitmap buffer index is changed would make
> > less disk access, improving performance especially for truncate operation.
> >
> > Testing with Samsung 256GB sdcard, mounted with dirsync option (mount
> > -t exfat /dev/block/mmcblk0p1 /temp/mount -o dirsync)
> >
> > Remove 4GB file, blktrace result.
> > [Before] : 39 secs.
> > Total (blktrace):
> >  Reads Queued:      0,        0KiB	 Writes Queued:      32775,
> 16387KiB
> >  Read Dispatches:   0,        0KiB	 Write Dispatches:   32775,
> 16387KiB
> >  Reads Requeued:    0		         Writes Requeued:        0
> >  Reads Completed:   0,        0KiB	 Writes Completed:   32775,
> 16387KiB
> >  Read Merges:       0,        0KiB	 Write Merges:           0,
> 0KiB
> >  IO unplugs:        2        	     Timer unplugs:          0
> >
> > [After] : 1 sec.
> > Total (blktrace):
> >  Reads Queued:      0,        0KiB	 Writes Queued:         13,
> 6KiB
> >  Read Dispatches:   0,        0KiB	 Write Dispatches:      13,
> 6KiB
> >  Reads Requeued:    0		         Writes Requeued:        0
> >  Reads Completed:   0,        0KiB	 Writes Completed:      13,
> 6KiB
> >  Read Merges:       0,        0KiB	 Write Merges:           0,
> 0KiB
> >  IO unplugs:        1        	     Timer unplugs:          0
> >
> > Signed-off-by: Hyeongseok Kim <hyeongseok@gmail.com>
> 
> Looks good.
> Thanks for your work!
> 
> Acked-by: Sungjong Seo <sj1557.seo@samsung.com>
Applied. Thanks!