Tejun Heo wrote:
Jeff Garzik wrote:
Tejun Heo wrote:
Instead of limiting max_sectors to 15 unconditionally, this patch
leaves max_sectors at the default value and process write requests
larger than 15 sectors by processing them in <= 15 sectors chunks.
This results in unhamplered read performance and better write
performance.
Split request processing is performed only for DMA write requests > 15
sectors. dev->max_sectors is limited to 15 sectors when the device is
put into PIO mode.
Signed-off-by: Tejun Heo <htejun@xxxxxxxxx>
I'm still put off by the complexity that this adds to each transfer,
and to the overall driver itself.
It's largely older chips and drives, so I don't think it's worth
carrying this code for decades to come, just for some early SATA
screwups.
Hey, you are the one who said that this can be included in the mainline.
I agree that this is a complex workaround, but...
* There are quite some number of users out there. My sil m15w
workaround page has quite some visitors and many of them are returning
visitors.
* The workaround kicks in only under certain circumstances, so it's not
like it adds overhead to normal command processing.
* It's complex but I've been carrying this around for quite some time
now and it's pretty easy to maintain. If you prefer, I can put all the
workaround implementation inside #if 1 .. #endif, so it can be dropped
very easily in the future.
I think it's worthwhile to have the workaround included. It has real
users out there and they benefit a lot from it. Complexity is contained
inside sata_sil proper and it has been shown that maintenance overhead
isn't too big.
I'll even put /* feel free to turn off #if for m15w workaround if it
causes any problem to new feature/bug fix/whatsoever. I'll follow up
and update it accordingly. */ comment above it.
Sorry, I just think it adds too much complexity to sata_sil itself. If
the driver ever grows PIO-DMA support, it may make sense in that case,
since you would need the complexity (sil context) anyway.
Seeing the patch, and comparing with the current driver, really weights
in favor of the current more-simple driver. There are a lot of
"early-rev hardware bug" things that we just don't bother with in Linux,
and I think this is one of them.
Jeff
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