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Fri, 8 Nov 2024 17:43:46 +0000 (GMT) X-AuditID: cbfec7f4-c0df970000004fb9-63-672e4dd2bfed Received: from eusmtip2.samsung.com ( [203.254.199.222]) by eusmgms1.samsung.com (EUCPMTA) with SMTP id 90.5E.19920.2DD4E276; Fri, 8 Nov 2024 17:43:46 +0000 (GMT) Received: from CAMSVWEXC01.scsc.local (unknown [106.1.227.71]) by eusmtip2.samsung.com (KnoxPortal) with ESMTPA id 20241108174346eusmtip2abf966de362f7009f8a57951f83f683b~GDzTaqMPi0139401394eusmtip2t; Fri, 8 Nov 2024 17:43:46 +0000 (GMT) Received: from CAMSVWEXC02.scsc.local (2002:6a01:e348::6a01:e348) by CAMSVWEXC01.scsc.local (2002:6a01:e347::6a01:e347) with Microsoft SMTP Server (TLS) id 15.0.1497.2; Fri, 8 Nov 2024 17:43:45 +0000 Received: from CAMSVWEXC02.scsc.local ([::1]) by CAMSVWEXC02.scsc.local ([fe80::3c08:6c51:fa0a:6384%13]) with mapi id 15.00.1497.012; Fri, 8 Nov 2024 17:43:45 +0000 From: Javier Gonzalez To: Matthew Wilcox , Keith Busch CC: Christoph Hellwig , Keith Busch , "linux-block@vger.kernel.org" , "linux-nvme@lists.infradead.org" , "linux-scsi@vger.kernel.org" , "io-uring@vger.kernel.org" , "linux-fsdevel@vger.kernel.org" , "joshi.k@samsung.com" , "bvanassche@acm.org" Subject: RE: [PATCHv10 0/9] write hints with nvme fdp, scsi streams Thread-Topic: [PATCHv10 0/9] write hints with nvme fdp, scsi streams Thread-Index: AQHbMelWveOK6b2iGEK3X1RaPLnLz7KtiFWAgAARngCAAAxgsA== Date: Fri, 8 Nov 2024 17:43:44 +0000 Message-ID: In-Reply-To: Accept-Language: en-US, en-GB Content-Language: en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted Content-Type: text/plain; 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Keith Busch ; linux- > block@vger.kernel.org; linux-nvme@lists.infradead.org; linux-scsi@vger.ke= rnel.org; > io-uring@vger.kernel.org; linux-fsdevel@vger.kernel.org; joshi.k@samsung.= com; > Javier Gonzalez ; bvanassche@acm.org > Subject: Re: [PATCHv10 0/9] write hints with nvme fdp, scsi streams >=20 > On Fri, Nov 08, 2024 at 08:51:31AM -0700, Keith Busch wrote: > > On Fri, Nov 08, 2024 at 03:18:52PM +0100, Christoph Hellwig wrote: > > > We're not really duplicating much. Writing sequential is pretty easy= , > > > and tracking reclaim units separately means you need another tracking > > > data structure, and either that or the LBA one is always going to be > > > badly fragmented if they aren't the same. > > > > You're getting fragmentation anyway, which is why you had to implement > > gc. You're just shifting who gets to deal with it from the controller t= o > > the host. The host is further from the media, so you're starting from a > > disadvantage. The host gc implementation would have to be quite a bit > > better to justify the link and memory usage necessary for the copies > > (...queue a copy-offload discussion? oom?). >=20 > But the filesystem knows which blocks are actually in use. Sending > TRIM/DISCARD information to the drive at block-level granularity hasn't > worked out so well in the past. So the drive is the one at a disadvantag= e > because it has to copy blocks which aren't actually in use. It is true that trim has not been great. I would say that at least enterpri= se SSDs have fixed this in general. For FDP, DSM Deallocate is respected, whic= h Provides a good "erase" interface to the host. It is true though that this is not properly described in the spec and we sh= ould fix it. >=20 > I like the idea of using copy-offload though. We have been iterating in the patches for years, but it is unfortunately one of these series that go in circles forever. I don't think it is due to any specific problem, but mostly due to unaligned requests form different folks reviewing. Last time I talked to Damien he asked me to=20 send the patches again; we have not followed through due to bandwidth. If there is an interest, we can re-spin this again...