You mean it implements its own make_request function? It'll still have queue limits - bcache works similarly. They might not be exported in sysfs though... I'll have a look at the driver. On Thu, May 10, 2012 at 2:00 AM, moussa ba <musaba@xxxxxxxxx> wrote: > Well, that might be the problem, there is no such entry. The driver is > basically a fake ahci driver and handles the bios directly. It is extremely > fast and the driver was written for very low latency IO hence the weird > driver stack. > > http://lxr.linux.no/linux+v3.3.5/drivers/block/mtip32xx/mtip32xx.c#L3044. > The mtip_make_request call fails whenever the number of entries in the SGL >> 128... > > Moussa > > On May 9, 2012 6:02 PM, "Kent Overstreet" <koverstreet@xxxxxxxxxx> wrote: >> >> That sounds like a bug in bcache - bcache should be respecting the >> queue limits the underlying device exports. >> >> Can you tell me what the various files in /sys/block/<device>/queue/ >> look like for your device? >> >> On Wed, May 9, 2012 at 8:23 PM, moussa ba <musaba@xxxxxxxxx> wrote: >> > Tried to send this to mailing list but was rejected somehow. >> > >> > ---------- Forwarded message ---------- >> > From: moussa ba <musaba@xxxxxxxxx> >> > Date: Wed, May 9, 2012 at 5:17 PM >> > Subject: Scatter Gather List in bio exceed driver capabilities >> > To: linux-bcache@xxxxxxxxxxxxxxx >> > >> > >> > >> > We are using a micron PCI-E SSD as a caching device. I am running into >> > issues where the driver would fail when we try to register the cache >> > device. >> > The failure is because bcache sends down a bio with 256 entries while >> > the >> > device driver can only handle 128 entries. We could make changes inside >> > our >> > driver to chunk the requests (mind you I did not write the driver, but >> > driver guys told me so...) and fix it that way. I am assuming that >> > since >> > bcache is creating the bio to get at its metadata, it does not chunk the >> > bios to fit the underlying hardware nor does it query it in some way to >> > set >> > the bi_vcnt. >> > >> > Any suggestions on how to properly address this? >> > >> > Moussa >> > -- To unsubscribe from this list: send the line "unsubscribe linux-bcache" in the body of a message to majordomo@xxxxxxxxxxxxxxx More majordomo info at http://vger.kernel.org/majordomo-info.html
