At 08:24 PM 10/07/2002 -0700, Andrew Morton wrote:
> > 2.5.25 ('virgin' 2.5.25 with the exception of changing PAGE_OFFSET to
> > 0x80000000 and
> > your O_DIRECT-on-blockdev patch to stop it oopsing -- oops report
> > below)
> > normal 167772160 blocks of 512 bytes in 607 seconds (134.81
> > mbyte/sec), CPUs 0% idle
> > O_DIRECT 20480 blocks of 4194304 bytes in 420 seconds (194.61
> > mbyte/sec), CPUs ~93% idle
> > /dev/rawN 20480 blocks of 4194304 bytes in 422 seconds (193.84
> > mbyte/sec), CPUs ~92% idle
>
>The 30% improvement in pagecache-buffered reads is somewhat unexpected.
>The blockdevs are not using multipage BIOs - they're still using
>buffer_head-based I/O for both reads and writes. Are you sure that
>the 2.4 QLogic driver is using block-highmem?
pretty sure -- there's no highmem in the system: :-)
(i.e. i changed PAGE_OFFSET in order to prevent there being any highmem).
[root@mel-stglab-host1 root]# cat /proc/meminfo
MemTotal: 1945680 kB
MemFree: 1853812 kB
MemShared: 0 kB
Cached: 29536 kB
SwapCached: 2520 kB
Active: 32336 kB
Inactive: 8336 kB
HighTotal: 0 kB
HighFree: 0 kB
LowTotal: 1945680 kB
LowFree: 1853812 kB
SwapTotal: 2047992 kB
SwapFree: 2037268 kB
Dirty: 1396 kB
Writeback: 0 kB
>OK, so there's nothing there at all really (or there may be. Hard
>to tell when the interface has saturated).
>
>But on my lowly scsi disks I was seeing no change in read bandwidth
>either. Only writes benefitted for some reason. Can you do
>some write testing as well? If you test writes through the pagecache,
>use ext2 and not direct-to-blockdev please - that'll take the multipage
>BIOs, buffer_head-bypass route. Plain old read and write of /dev/XdYY
>isn't very optimised at all.
will do.
do you have any other preferences --
- ext2 or ext3?
- if ext3, change the journalling mode?
- i/o to a single large file or multiple files per spindle?
i can also add combinations of read/write & seeking also.
what kind of file-size should i be using?
cheers,
lincoln.
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This archive was generated by hypermail 2b29 : Mon Jul 15 2002 - 22:00:19 EST