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[84.110.32.226]) by smtp.gmail.com with ESMTPSA id 5b1f17b1804b1-421542e207esm13638365e9.22.2024.06.04.06.01.18 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Tue, 04 Jun 2024 06:01:20 -0700 (PDT) Message-ID: Date: Tue, 4 Jun 2024 16:01:17 +0300 Precedence: bulk X-Mailing-List: ceph-devel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 User-Agent: Mozilla Thunderbird Subject: Re: [PATCH v2 1/4] net: introduce helper sendpages_ok() From: Sagi Grimberg To: Christoph Hellwig Cc: Ofir Gal , davem@davemloft.net, linux-block@vger.kernel.org, linux-nvme@lists.infradead.org, netdev@vger.kernel.org, ceph-devel@vger.kernel.org, dhowells@redhat.com, edumazet@google.com, pabeni@redhat.com, kbusch@kernel.org, axboe@kernel.dk, philipp.reisner@linbit.com, lars.ellenberg@linbit.com, christoph.boehmwalder@linbit.com, idryomov@gmail.com, xiubli@redhat.com References: <20240530142417.146696-1-ofir.gal@volumez.com> <20240530142417.146696-2-ofir.gal@volumez.com> <8d0c198f-9c15-4a8f-957a-2e4aecddd2e5@grimberg.me> <23821101-adf0-4e38-a894-fb05a19cb9c3@volumez.com> <86e60615-9286-4c9c-bffc-72304bd3cc1f@grimberg.me> <20240604042738.GA28853@lst.de> <62c2b8cd-ce6a-4e13-a58c-a6b30a0dcf17@grimberg.me> Content-Language: en-US In-Reply-To: <62c2b8cd-ce6a-4e13-a58c-a6b30a0dcf17@grimberg.me> Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit On 04/06/2024 11:24, Sagi Grimberg wrote: > > > On 04/06/2024 7:27, Christoph Hellwig wrote: >> On Tue, Jun 04, 2024 at 12:27:06AM +0300, Sagi Grimberg wrote: >>>>> I still don't understand how a page in the middle of a contiguous >>>>> range ends >>>>> up coming from the slab while others don't. >>>> I haven't investigate the origin of the IO >>>> yet. I suspect the first 2 pages are the superblocks of the raid >>>> (mdp_superblock_1 and bitmap_super_s) and the rest of the IO is the >>>> bitmap. >>> Well, if these indeed are different origins and just *happen* to be a >>> mixture >>> of slab originated pages and non-slab pages combined together in a >>> single >>> bio of a bvec entry, >>> I'd suspect that it would be more beneficial to split the bvec >>> (essentially >>> not allow bio_add_page >>> to append the page to tail bvec depending on a queue limit (similar >>> to how >>> we handle sg gaps). >> So you want to add a PageSlab check to bvec_try_merge_page? That sounds >> fairly expensive.. >> > > The check needs to happen somewhere apparently, and given that it will > be gated by a queue flag > only request queues that actually needed will suffer, but they will > suffer anyways... Something like the untested patch below: -- diff --git a/block/bio.c b/block/bio.c index 53f608028c78..e55a4184c0e6 100644 --- a/block/bio.c +++ b/block/bio.c @@ -18,6 +18,7 @@  #include  #include  #include +#include  #include  #include "blk.h" @@ -960,6 +961,9 @@ bool bvec_try_merge_hw_page(struct request_queue *q, struct bio_vec *bv,                 return false;         if (len > queue_max_segment_size(q) - bv->bv_len)                 return false; +       if (q->limits.splice_pages && +           sendpage_ok(bv->bv_page) ^ sendpage_ok(page)) +                       return false;         return bvec_try_merge_page(bv, page, len, offset, same_page);  } diff --git a/drivers/nvme/host/core.c b/drivers/nvme/host/core.c index a7e820840cf7..82e2719acb9c 100644 --- a/drivers/nvme/host/core.c +++ b/drivers/nvme/host/core.c @@ -1937,6 +1937,7 @@ static void nvme_set_ctrl_limits(struct nvme_ctrl *ctrl,         lim->virt_boundary_mask = NVME_CTRL_PAGE_SIZE - 1;         lim->max_segment_size = UINT_MAX;         lim->dma_alignment = 3; +       lim->splice_pages = ctrl->splice_pages;  }  static bool nvme_update_disk_info(struct nvme_ns *ns, struct nvme_id_ns *id, diff --git a/drivers/nvme/host/nvme.h b/drivers/nvme/host/nvme.h index 3f3e26849b61..d9818330e236 100644 --- a/drivers/nvme/host/nvme.h +++ b/drivers/nvme/host/nvme.h @@ -398,6 +398,7 @@ struct nvme_ctrl {         enum nvme_ctrl_type cntrltype;         enum nvme_dctype dctype; +       bool splice_pages  };  static inline enum nvme_ctrl_state nvme_ctrl_state(struct nvme_ctrl *ctrl) diff --git a/drivers/nvme/host/tcp.c b/drivers/nvme/host/tcp.c index 02076b8cb4d8..618b8f20206a 100644 --- a/drivers/nvme/host/tcp.c +++ b/drivers/nvme/host/tcp.c @@ -2146,6 +2146,12 @@ static int nvme_tcp_configure_admin_queue(struct nvme_ctrl *ctrl, bool new)         if (error)                 goto out_stop_queue; +       /* +        * we want to prevent contig pages with conflicting splice-ability with +        * respect to the network transmission +        */ +       ctrl->splice_pages = true; +         nvme_unquiesce_admin_queue(ctrl);         error = nvme_init_ctrl_finish(ctrl, false); diff --git a/include/linux/blkdev.h b/include/linux/blkdev.h index 69c4f113db42..ec657ddad2a4 100644 --- a/include/linux/blkdev.h +++ b/include/linux/blkdev.h @@ -331,6 +331,12 @@ struct queue_limits {          * due to possible offsets.          */         unsigned int            dma_alignment; + +       /* +        * Drivers that use MSG_SPLICE_PAGES to send the bvec over the network, +        * will need either bvec entry contig pages spliceable or not. +        */ +       bool                    splice_pages;  };  typedef int (*report_zones_cb)(struct blk_zone *zone, unsigned int idx, -- What I now see is that we will check PageSlab twice (bvec last index and append page) and skb_splice_from_iter checks it again... How many times check we check this :) Would be great if the network stack can just check it once and fallback to page copy...