Re: poor sata performance on 2.6

[Jeff Garzik]

Denis Vlasenko wrote:
> On Thursday 15 April 2004 17:48, Konstantin Sobolev wrote:
>
> > On Thursday 15 April 2004 18:33, Justin Cormack wrote:
> >
> > > On Thu, 2004-04-15 at 15:26, Konstantin Sobolev wrote:
> > >
> > > > On Thursday 15 April 2004 18:00, Justin Cormack wrote:
> > > >
> > > > > hmm, odd. I get 50MB/s or so from normal (7200, 8MB cache) WD disks,
> > > > > and Seagate from the same controller. Can you send lspci,
> > > > > /proc/interrupts and dmesg...
> > > >
> > > > Attached are files for 2.6.5-mm5 with highmem, ACPI and APIC turned
> > > > off.
> > >
> > > ah. Make a filesystem on it and mount it and try again. I see you have
> > > no partition table and so probably no filesystem. This means the block
> > > size is set to default 512byte not 4k which makes disk operations slow.
> > > Any filesystem should default to block size of 4k, eg ext2.
> >
> > Very interesting!
> > created partition table,
> > kos sata # mkfs.ext2 /dev/sda1
> > [..skipped..]
> > kos mnt # cd /
> > kos / # mkdir wd
> > kos / # mount /dev/sda1 /wd
> > kos / # hdparm -t -a8192 /dev/sda
> >
> > /dev/sda:
> > setting fs readahead to 8192
> > readahead    = 8192 (on)
> > Timing buffered disk reads:   82 MB in  3.03 seconds =  27.02 MB/sec
> >
> > kos / # mount | grep sda
> > /dev/sda1 on /wd type ext2 (rw)
> > kos / # hdparm -t -a8192 /dev/sda
> >
> > /dev/sda:
> > setting fs readahead to 8192
> > readahead    = 8192 (on)
> > Timing buffered disk reads:  206 MB in  3.02 seconds =  68.15 MB/sec
> > kos / # hdparm -t -a8192 /dev/sda
> >
> > /dev/sda:
> > setting fs readahead to 8192
> > readahead    = 8192 (on)
> > Timing buffered disk reads:  206 MB in  3.02 seconds =  68.18 MB/sec
> >
> > So first time it gave the same loosy 27 MB/s and subsequent tests give
> > pretty good 68 MB/s! Why?
>
>
> Time to CC ide/libata/block layer folks
>
> Jeff Garzik <jgarzik@xxxxxxxxx>
> 	libata man


It seems like the situation is already resolved, to me.

When you mount a filesystem, it changes the default block size (512 or 
1024) to the filesystem block size, normally 4096.  This would certainly 
increase the throughput.

	Jeff



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