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a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1745415584; bh=S0WcvfERookrfqdsNf09r0AEV1z7UbVgPAAe8PW/qEQ=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=C7fbCECKz3kHNJ+jo+OIrSy4DZWF6VfP/zMT2YhsyEeG8iSKLjTEeP4BGX7t1v67F p+smI3psobdO3tCjGOBUD38dcg+HJceGigztEe+RqIFgjXeSmBqGusz82SrUq7Iqhr 6YBAvgVdMKqIXI9geSfRtO4adJnuAwKrlMzGN0FoYiFnp8djUeWrTDRnjGiNRjdms1 lVhbJbHhBl3bRbYk7Z4X83FROH2nhn6Tw5OSDGilthlPt/WSsdwmadbLXjVpawj9FS VkdfwLWiAYzGPR8yiCx1MEJV3iIN1dHQZZLErOM+ocSreR4LOhSFYEGHNzjW661Mct C0lSied3DnKWA== Date: Wed, 23 Apr 2025 16:39:39 +0300 From: Leon Romanovsky To: Christoph Hellwig Cc: Marek Szyprowski , Jens Axboe , Keith Busch , Jake Edge , Jonathan Corbet , Jason Gunthorpe , Zhu Yanjun , Robin Murphy , Joerg Roedel , Will Deacon , Sagi Grimberg , Bjorn Helgaas , Logan Gunthorpe , Yishai Hadas , Shameer Kolothum , Kevin Tian , Alex Williamson , =?iso-8859-1?B?Suly9G1l?= Glisse , Andrew Morton , linux-doc@vger.kernel.org, linux-kernel@vger.kernel.org, linux-block@vger.kernel.org, linux-rdma@vger.kernel.org, iommu@lists.linux.dev, linux-nvme@lists.infradead.org, linux-pci@vger.kernel.org, kvm@vger.kernel.org, linux-mm@kvack.org, Niklas Schnelle , Chuck Lever , Luis Chamberlain , Matthew Wilcox , Dan Williams , Kanchan Joshi , Chaitanya Kulkarni Subject: Re: [PATCH v9 22/24] nvme-pci: use a better encoding for small prp pool allocations Message-ID: <20250423133939.GJ48485@unreal> References: <973ed41249e12766383b3cedac799692f9bda3b8.1745394536.git.leon@kernel.org> <20250423090552.GA381@lst.de> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20250423090552.GA381@lst.de> X-Rspamd-Queue-Id: BE6DA140008 X-Stat-Signature: h7dki4ze9gea7989bmdiz1ei4ry5oapk X-Rspam-User: X-Rspamd-Server: rspam08 X-HE-Tag: 1745415585-958966 X-HE-Meta: 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 gD3D+dAb Gm/omiKb3Mf5XfQvWNPLjqZ2u/TZZ81On23Z0rmjufr34fHkN96wymHPvj+R0uCDrN1slqI1oTi5gOkSGxEWu1TtKEkf4y3sJvwbc3drKi1Wegpr2LBdyf6BJeec84Ki8DyG8X36JeHkE0PsE/XkXwAvtuflNABMrjfDqDsVzQhz8BusWSL9GOky+8FPsJ1tohq826WnHIpowstFelCto/06OtqpV/frtJyrXXty5ovp7RxpeJ48sOmDpJg7mbpkV3PQ6jVIHkYhdCWR1LfQsMLODNwwbRU/QORgYJb3BwEIQWz4= X-Bogosity: Ham, tests=bogofilter, spamicity=0.000000, version=1.2.4 Sender: owner-linux-mm@kvack.org Precedence: bulk X-Loop: owner-majordomo@kvack.org List-ID: List-Subscribe: List-Unsubscribe: On Wed, Apr 23, 2025 at 11:05:52AM +0200, Christoph Hellwig wrote: > On Wed, Apr 23, 2025 at 11:13:13AM +0300, Leon Romanovsky wrote: > > From: Christoph Hellwig > > > > There is plenty of unused space in the iod next to nr_descriptors. > > Add a separate flag to encode that the transfer is using the full > > page sized pool, and use a normal 0..n count for the number of > > descriptors. > > > > Signed-off-by: Christoph Hellwig > > Tested-by: Jens Axboe > > [ Leon: changed original bool variable to be flag as was proposed by Kanchan ] > > Signed-off-by: Kanchan Joshi > > Signed-off-by: Leon Romanovsky > > --- > > drivers/nvme/host/pci.c | 93 ++++++++++++++++++++--------------------- > > 1 file changed, 46 insertions(+), 47 deletions(-) > > > > diff --git a/drivers/nvme/host/pci.c b/drivers/nvme/host/pci.c > > index 638e759b29ad..7e93536d01cb 100644 > > --- a/drivers/nvme/host/pci.c > > +++ b/drivers/nvme/host/pci.c > > @@ -44,6 +44,7 @@ > > #define NVME_MAX_SEGS 128 > > #define NVME_MAX_META_SEGS 15 > > #define NVME_MAX_NR_DESCRIPTORS 5 > > +#define NVME_SMALL_DESCRIPTOR_SIZE 256 > > > > static int use_threaded_interrupts; > > module_param(use_threaded_interrupts, int, 0444); > > @@ -219,6 +220,10 @@ struct nvme_queue { > > struct completion delete_done; > > }; > > > > +enum { > > + IOD_LARGE_DESCRIPTORS = 1, /* uses the full page sized descriptor pool */ > > This is used as a ORable flag, I'd make that explicit: > > /* uses the full page sized descriptor pool */ > IOD_LARGE_DESCRIPTORS = 1U << 0, > > and similar for the next flag added in the next patch. > > > struct nvme_request req; > > struct nvme_command cmd; > > bool aborted; > > - /* # of PRP/SGL descriptors: (0 for small pool) */ > > - s8 nr_descriptors; > > + u8 nr_descriptors; /* # of PRP/SGL descriptors */ > > + unsigned int flags; > > And this should be limited to a u16 to not bloat the structure. I'll limit it to u8. Thanks >