Disable aggregation of requests to a block device

[Erez Zilber]

Hi,

I'm running I/O to a block device (which is an iSCSI device, but that
shouldn't matter), usually with transfer length = 128kB. From time to
time, I see that 2 128kB commands get aggregated to a single 256kB
command, which is bad for me because the resources that I allocate are
based on 128kB commands. I could limit the command size by setting
/sys/block/sdX/queue/max_sectors_kb to 128kB, but sometimes I expect
larger commands (e.g. 512kB), and I don't want the block layer to
split them into smaller commands.

My question is: can I disable this aggregation? If yes, how? Else, is
there another solution?

Thanks,
Erez
--
To unsubscribe from this list: send the line "unsubscribe linux-kernel" in
the body of a message to majordomo@xxxxxxxxxxxxxxx
More majordomo info at  http://vger.kernel.org/majordomo-info.html
Please read the FAQ at  http://www.tux.org/lkml/