Date: Mon, 14 Dec 2009 13:27:21 +0200 From: Alexander Motin <mav@FreeBSD.org> To: Ivan Voras <ivoras@freebsd.org> Cc: FreeBSD-Current <freebsd-current@freebsd.org> Subject: Re: How do I use NCQ of Intel X25-E(SSD) on ahci(4)? Message-ID: <4B262119.6090904@FreeBSD.org> In-Reply-To: <1258590193.00184983.1258579804@10.7.7.3> References: <1258575782.00184876.1258562404@10.7.7.3> <mailpost.1258563606.7337474.35089.mailing.freebsd.current@FreeBSD.cs.nctu.edu.tw> <1258579386.00184908.1258567802@10.7.7.3> <1258590193.00184983.1258579804@10.7.7.3>
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Ivan Voras wrote: > 2009/11/18 Alexander Motin <mav@freebsd.org>: >> Ivan Voras wrote: > >>> I know next to nothing about AHCI and drivers so this might be obviously >>> wrong but wouldn't a quick (i.e. MFC-able) obvious temporary fix be to say >>> >>> numslots = min(get_minimum_tags_of_all_drives(), ...) >>> ? >> Problem is that SIM driver has no idea about devices capabilities, and >> also doesn't have method to resize queue after attach. In SCSI case, >> tags are random and only simultaneous number of request is limited, and >> this is handled fine by CAM. SATA NCQ is more restrictive, allowing to >> use only tags 0..(N-1). I am planning to make XPT inform SIM about >> supported tags for each device, to allow SIM to use that information >> while scheduling requests. I didn't do it yet, just because most of >> devices able to handle all 32 tags possible on SATA. This Intel SSD is >> one of rare exceptions. > > Ok, (still thinking about something that could be MFC-able in an > emergency), how about adding a loader tunable integer instead of "32"? Just for note, it is already fixed and merged. -- Alexander Motin
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