Painful speed for copying to fat32 partitions with small cluster size.

[Ion-Mihai Tetcu]

On Sun, 8 Feb 2004 09:19:04 +1100 (EST)
Bruce Evans <bde at zeta.org.au> wrote:

> On Sat, 7 Feb 2004, Ion-Mihai Tetcu wrote:
> 
> > Does anyone know why this happens or what to do ?
> >
> > Setup: UDMA133 primary master, UFS2; UDMA100 secondary master, FAT32.
> >
> > Copying to FAT32 partitions is very slow with small cluster sizes (I was
> > copying some 300 - 700MB files):
> >
> > FAT32 clustersize=4K	500KB/s
> > FAT32 clustersize=32K	3.5MB/s
> > FAT32 clustersize=64K	6.2MB/s
> > FAT32 clustersize=128K	6.4MB/s
> > FAT16			6.5MB/s
> >
> > Reading speed is the same.
> 
> Lots of things are suboptimal, including your disk apparently not liking
> small writes (or reads?).

I don't think reads are the problem; I cannot say for sure, since I
haven't done real testing, but I'll try. When I've said 'Reading speed
is the same.' I meant that I get the same reading speed no mater the
cluster size.

For reference:

Primary master (copying from) is:
<Maxtor 6Y120L0/YAR41BW0> ATA-7 disk at ata0-master
117246MB (240121728 sectors), 238216 C, 16 H, 63 S, 512 B
16 secs/int, 1 depth queue, UDMA133

and secondary slave (copying to) is:
<WDC WD1600JB-00EVA0/15.05R15> ATA-6 disk at ata1-master
152626MB (312579695 sectors), 310098 C, 16 H, 63 S, 512 B
16 secs/int, 1 depth queue, UDMA100

the controller is:
VIA 8237 chip

> Try this patch:

Thank you, I'll try it in about a week or so, since I don't have the
disk in anymore.

> %%%
> Index: msdosfs_vnops.c
> ===================================================================
> RCS file: /home/ncvs/src/sys/fs/msdosfs/msdosfs_vnops.c,v
> retrieving revision 1.147
> diff -u -2 -r1.147 msdosfs_vnops.c
> --- msdosfs_vnops.c	4 Feb 2004 21:52:53 -0000	1.147
> +++ msdosfs_vnops.c	5 Feb 2004 08:11:38 -0000
> @@ -771,5 +791,9 @@
>  			(void) bwrite(bp);
>  		else if (n + croffset == pmp->pm_bpcluster)
> +#if 0
>  			bawrite(bp);
> +#else
> +			bdwrite(bp);
> +#endif
>  		else
>  			bdwrite(bp);
> %%%
> 
> With it, I get 3+ MB/sec from iozone with a write size of 4K to a file
> system with a cluster size of 4K on an old 6.3GB drive with 9MB/sec max
> transfer speed, and writing 512-blocks is not much slower.  Without it,
> writing 4K blocks goes fast enough but writing 2K blocks is 10 times
> slower.
> 
> It won't help reads.

Reading seems ok, from both disks.

> See ffs_write() for a more complete version of this.   ffs_write()
> normally uses cluster_write() for the full-block case where the original
> version of the above uses foot-shooting; both ffs_write() and
> msdosfs_write() use bdwrite() for partial blocks and ffs_write() also
> sets B_CLUSTEROK for this and most other cases.  As fair as I understand,
> bdwrite() with B_CLUSTEROK is just as good as, if not better than
> cluster_write() (the former gives a delayed clustered write and the
> latter gives an immediate clustered write if the cluster is full and
> is no different otherwise; the advantage of cluster_write() is that it
> gives a better hint to vfs_bio that the write should be done soon).
> 
> > Newfs_msdos on a 30G partition:
> >
> > itetcu at it> /home/itetcu [16:31:40] 1
> > # newfs_msdos -F32 -b65536 /dev/ad2s1
> > /dev/ad2s1: 167746176 sectors in 1310517 FAT32 clusters (65536 bytes/cluster)
> > bps=512 spc=128 res=32 nft=2 mid=0xf0 spt=63 hds=16 hid=0 bsec=167766732 bspf=10239 rdcl=2 infs=1 bkbs=2
> > itetcu at it> /home/itetcu [16:34:48] 0
> > #
> >
> > The same with 4K clusters takes about 50 minutes !
> 
> Your disk apparently doesn't like writing 4K-blocks and mine apparently
> doesn't like writing 2K-blocks.  Write caching probably helps a lot here.

True, hw.ata.wc=0. BTW, with this setting atacotrol says:
Feature                      Support  Enable    Value   Vendor
write cache                    yes      yes
read ahead                     yes      yes

which confuses me.



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IOnut
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