lists.openwall.net | lists / announce owl-users owl-dev john-users john-dev passwdqc-users yescrypt popa3d-users / oss-security kernel-hardening musl sabotage tlsify passwords / crypt-dev xvendor / Bugtraq Full-Disclosure linux-kernel linux-netdev linux-ext4 linux-hardening linux-cve-announce PHC | |
Open Source and information security mailing list archives
| ||
|
Date: Mon, 17 Aug 2009 00:24:23 -0400 From: Douglas Gilbert <dgilbert@...erlog.com> To: Christoph Hellwig <hch@...radead.org> CC: James Bottomley <James.Bottomley@...e.de>, Arjan van de Ven <arjan@...radead.org>, Alan Cox <alan@...rguk.ukuu.org.uk>, Mark Lord <liml@....ca>, Chris Worley <worleys@...il.com>, Matthew Wilcox <matthew@....cx>, Bryan Donlan <bdonlan@...il.com>, david@...g.hm, Greg Freemyer <greg.freemyer@...il.com>, Markus Trippelsdorf <markus@...ppelsdorf.de>, Matthew Wilcox <willy@...ux.intel.com>, Hugh Dickins <hugh.dickins@...cali.co.uk>, Nitin Gupta <ngupta@...are.org>, Ingo Molnar <mingo@...e.hu>, Peter Zijlstra <peterz@...radead.org>, linux-kernel@...r.kernel.org, linux-mm@...ck.org, linux-scsi@...r.kernel.org, linux-ide@...r.kernel.org, Linux RAID <linux-raid@...r.kernel.org> Subject: Re: Discard support (was Re: [PATCH] swap: send callback when swap slot is freed) Christoph Hellwig wrote: > On Sun, Aug 16, 2009 at 10:52:07AM -0500, James Bottomley wrote: >> However, the enterprise has been doing UNMAP for a while, so we can draw >> inferences from them since the SSD FTL will operate similarly. For >> them, UNMAP is the same cost in terms of time regardless of the number >> of extents. The reason is that it's moving the blocks from the global >> in use list to the global free list. Part of the problem is that this >> involves locking and quiescing, so UNMAP ends up being quite expensive >> to the array but constant in terms of cost (hence they want as few >> unmaps for as many sectors as possible). > > How are they doing the unmaps? Using something similar to Mark's wiper > script and using SG_IO? Because right now we do not actually implement > UNMAP support in the kernel. I'd really love to test the XFS batched > discard support with a real UNMAP implementation. The sg3_utils version 1.28 beta at http://sg.danny.cz/sg/ has a new sg_unmap utility and the previous release included sg_write_same with Unmap bit support. sg_readcap has been updated to show the TPE and TPRZ bits. There is a new SCSI GET LBA STATUS command coming (approved at the last t10 meeting, awaiting the next SBC-3 draft). That will show the mapped/unmapped status of logical blocks in a range of LBAs. I can add a utility for that as well. Doug Gilbert -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
Powered by blists - more mailing lists