From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Darrick J. Wong" Subject: Re: [PATCH 3/6] aio/dio: enable PI passthrough Date: Wed, 2 Apr 2014 15:55:37 -0700 Message-ID: <20140402225537.GE10230@birch.djwong.org> References: <20140324162231.10848.4863.stgit@birch.djwong.org> <20140324162251.10848.56452.stgit@birch.djwong.org> <20140402200133.GK2394@lenny.home.zabbo.net> <20140402204420.GB10230@birch.djwong.org> <20140402223311.GN2394@lenny.home.zabbo.net> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Cc: axboe@kernel.dk, martin.petersen@oracle.com, JBottomley@parallels.com, jmoyer@redhat.com, bcrl@kvack.org, viro@zeniv.linux.org.uk, linux-fsdevel@vger.kernel.org, linux-aio@kvack.org, linux-scsi@vger.kernel.org, linux-mm@kvack.org To: Zach Brown Return-path: Content-Disposition: inline In-Reply-To: <20140402223311.GN2394@lenny.home.zabbo.net> Sender: owner-linux-aio@kvack.org List-Id: linux-fsdevel.vger.kernel.org On Wed, Apr 02, 2014 at 03:33:11PM -0700, Zach Brown wrote: > > One thing I'm not sure about: What's the largest IO (in terms of # of blocks, > > not # of struct iovecs) that I can throw at the kernel? > > Yeah, dunno. I'd guess big :). I'd hope that the PI code already has a > way to clamp the size of bios if there's a limit to the size of PI data > that can be managed downstream? I guess if we restricted the size of the PI buffer to a page's worth of pointers to struct page, that limits us to 128M on x64 with DIF and 512b sectors. That's not really a whole lot; I suppose one could (ab)use vmalloc. Yes, blk-integrity clamps the size of the bio to fit the downstream device's maximum integrity sg size. See max_integrity_segments for details, or the mostly-undocumented sg_prot_tablesize sysfs attribute that reveals it. I don't know what a practical limit is; scsi_debug sets it to 65536. --D > > - z > -- > To unsubscribe from this list: send the line "unsubscribe linux-fsdevel" in > the body of a message to majordomo@vger.kernel.org > More majordomo info at http://vger.kernel.org/majordomo-info.html -- To unsubscribe, send a message with 'unsubscribe linux-aio' in the body to majordomo@kvack.org. For more info on Linux AIO, see: http://www.kvack.org/aio/ Don't email: aart@kvack.org