Messages in this thread |  | | Date | Sun, 4 Nov 2001 06:23:47 +0100 (CET) | From | Gérard Roudier <> | Subject | Re: Adaptec vs Symbios performance |
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On Sat, 3 Nov 2001, Justin T. Gibbs wrote:
[...]
> >I can see _both_ comparing aic with symbios. > > I'm not sure that you would see much of a difference if you set the > symbios driver to use 253 commands per-device. I haven't looked at
This is discouraged. :) Better, IMO, to compare behaviours with realistic queue depths. As you know, more than 64 for hard disks does not make sense (yet). Personnaly, I use 64 under FreeBSD and 16 under Linux. Guess why ? :-)
> the sym driver for some time, but last I remember it does not use > a bottom half handler and handles queue throttling internally. It
There is no BH in the driver. The stock sym53c8xx even uses scsi_obsolete that requires more load in interrupt context for command completion. SYM-2 that comes back from FreeBSD uses the EH threaded stuff that just queues to a BH on completion. Stephan may want to give SYM-2 a try, IMO.
> may perform less work at interrupt time than the aic7xxx driver if > locally queued I/O is compiled into a format suitable for controller > consumption rather than queue the ScsiCmnd structure provided by > the mid-layer. The aic7xxx driver has to convert a ScsiCmnd into a > controller data structure to service an internal queue and this can > take a bit of time.
The sym* drivers also uses an internal data structure to handle I/Os. The SCSI script does not know about any O/S specific data structure.
> I would be interresting if there is a disparity in the TPS numbers > and tag depths in your comparisons. Higher tag depth usually means > higher TPS which may also mean less interactive response from the > system. All things being equal, I would expect the sym and aic7xxx > drivers to perform about the same.
Agreed.
Gérard.
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