Am 02.07.2011 um 15:50 schrieb Hannes Reinecke <h...@suse.de>:
> On 07/01/2011 06:42 PM, Alexander Graf wrote: >> >> On 01.07.2011, at 17:35, Hannes Reinecke wrote: >> >>> This patch adds an emulation for the LSI Megaraid SAS 8708EM2 HBA. >> >> Have you tried to execute the current version of megasas and actually > > do something with it? I just booted up openSUSE 11.4 rescue from DVD > > with a megasas adapter that contained a raw file backed by tmpfs. > > Creating a partition worked fine, but when running mkfs.ext3 and > > mounting afterwards, the mount fails saying there is no ext3 on the disk. >> >> Sounds like data corruption to me :). I know that this used to work > > a while back, so it might be a regression recently? >> > It worked here, in the sense that I've booted up an existing openSUSE 11.4 > installation. But I wouldn't be surprised if the degradation to use > bounce-buffers has some flaws. > > My guess here is that we have problems when the transfersizes larger as the > internal bounce buffer. Ah, might be a good idea to have some check for that. Just assert() out when the bounce buffer is too small - or at least tell the user about it. Can the iov functions tell you if you exceed the write/read side? > > (I probably should be putting in some more references to 'bounce buffers' > here to alert people that using bounce buffers in SCSI is the best way of > killing performance) > (And no, I will not getting into another dog-fight with Paul B. here. > Virtio can do without bounce buffers. AHCI can. So I fail to see why SCSI has > to rely on bounce buffers.) My hope is that by approaching this incrementally, we can move to a 0-copy approach later on. But for now, let's focus on getting the device emulation part well working an in. > > But enough of this, Yeah, bugfixing is needed here. I see what I can do. Thanks :) Alex >
