From patchwork Tue Dec 3 15:31:47 2024 Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: 7bit X-Patchwork-Submitter: Jens Axboe X-Patchwork-Id: 13892615 Received: from mail-oi1-f170.google.com (mail-oi1-f170.google.com [209.85.167.170]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 70FDF208964 for ; Tue, 3 Dec 2024 15:33:02 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.167.170 ARC-Seal: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733239984; cv=none; b=iYO4g/CfkzoKZm77ZMMqH2hGQGKxsKJlIPWxfF3hqGQWpnCwuHOS0jzVtvPorCvyQJSpgK3tEtL1bq9FDRUw08kmrLFQLOvk7UGQp2W5IGBrEaXpHHFpXVJOZ59YEVeVVg+Bax5U3+AZJav42JCzIhhjHgumDUD1sklSH0O+pD0= ARC-Message-Signature: i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1733239984; c=relaxed/simple; bh=H+SJrhFgkMARuJzf6zQzkW6swewkOc9KT1deZMH8OhQ=; h=From:To:Cc:Subject:Date:Message-ID:In-Reply-To:References: MIME-Version; b=PJLu5bUZouaxqAzhweO2G8KQLbIP9xGY/gRVLUKuhFtQndyT9LiF942FEe2zrxBEY4vo+r/9n8Dmc2lQbDNCyozwwYqr/L6X7Gz1a969VuVQqtsNe6dlq0+fKkFon5Jwab0tNiEJj8/q/HZVJCW9sBc5z+rQf6gqMve4TGFDB5Y= ARC-Authentication-Results: i=1; smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk; spf=pass smtp.mailfrom=kernel.dk; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b=NvPvt5h7; arc=none smtp.client-ip=209.85.167.170 Authentication-Results: smtp.subspace.kernel.org; dmarc=none (p=none dis=none) header.from=kernel.dk Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=kernel.dk Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=kernel-dk.20230601.gappssmtp.com header.i=@kernel-dk.20230601.gappssmtp.com header.b="NvPvt5h7" Received: by mail-oi1-f170.google.com with SMTP id 5614622812f47-3e786167712so2728156b6e.3 for ; Tue, 03 Dec 2024 07:33:02 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=kernel-dk.20230601.gappssmtp.com; s=20230601; t=1733239981; x=1733844781; darn=vger.kernel.org; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:from:to:cc:subject:date :message-id:reply-to; bh=rNRkYctWaLbO70YbebeuOKFfbUg5iKQfEN1xFJYmHB8=; b=NvPvt5h7l8lngjBGNuxy1XfMurd28jtD71TE5JEBJN8m0imAbUo5S3bdcA1KRVni0K adBG9tVcZH3XkpLeOYkphqHUsl8KthkdbhxTVwzY/AYvhuXK8Y1+2DFvCv6V01nqbG2e 3oUcfMTQszBNztI4erRKjKFbzvlrRZNoM57g/od4rXo89X13JlAbyf7VExy+ZafmwNUN TmnqZ40rMEAHhACUFoJrPsE14XGVVZYsZnLmmGH3lDZfNy7cR9Ctj/KxowZFTmsInge0 Bvoc8xEaEU5E2ZG/+QlgV/0AKK+JojGNNqffpdz0vhhgRX0cutoayz9fj9wDcLTW1kct 3org== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1733239981; x=1733844781; h=content-transfer-encoding:mime-version:references:in-reply-to :message-id:date:subject:cc:to:from:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=rNRkYctWaLbO70YbebeuOKFfbUg5iKQfEN1xFJYmHB8=; b=uk+RwACfSQKHEV9M5XO9sxsaey4/h2vjUrd54lsr3y1DNfeb9UxiZw8yRPEQkyMKHo 55OzejKPy0y/BzeZswpOYsTJl9seIgn63Ltgi5Z3k+TGPYRGXS2U5pOZUaEycqY0sM4g OjgNv67CpcxYA4d8/OOk+Im8fQJvaEZSZt9OrNR2wihGsfHmcPxDZt/2CYpCaTEJQXPe Q6tXR9SZZUZEpWBQMVw7laOsg8gXwAQISUziw4pZW8uEKgWK9/Xq3a2rOiG9OJR8A8O+ EShQQW/jBWD7UMQeiA3ihj/ovF+TNak0R4NukNxKl0Uv8ag+Ly/igJhdAhThO59q7PMp A5GQ== X-Forwarded-Encrypted: i=1; AJvYcCUnXUp2wYb+KhA5lm5+Ju69xe9NgY2kIHrDt4s3TXBLY0nZoyG+ptZR2S2uRc65QlgTjDy433JBtxDNrDDk@vger.kernel.org X-Gm-Message-State: AOJu0YxsjOuYsF7nOp4eA/acpGRHon2b48oxx4Xhm7dW7ib/H7luF2uk DWBK8e+WOyon1erexIR1mD3I6zKSlOMl2vcxEqSdVtHiE85GKGZnSrsr7xRdcnQ= X-Gm-Gg: ASbGncsVWdAFoMHyFCNXfWTG94swPshDmKS2K3k3gkc6RFMy+Kg7dYl/K+lX7rmiDgL ZIUeK+yBafZOvoQs8lu9JzXkB4LP8i3yMxVYiYcfMn466A/mp/fr2qrst4lNZlQpJjgoFL7WDk7 dK/uzfsXXpz3hGVtOwBJtuFuTwQO/pVpAXaGchWxXFR2cItGWqt5cllb5FuQpbtpaRmP5g+uLcr uV3Dt7ve7sL1Eclh6M1YZFulk6OQ91P3zQ+6nLJFvJjbb2Kf97+yfWVdAg= X-Google-Smtp-Source: AGHT+IGnmoFBWMRz09BuY3oNVVI/1OH4qyI0X8Y48goC/ICz9U7NJeNOcoRPtjmNOo7azkeA+JUnjQ== X-Received: by 2002:a05:6808:200d:b0:3e6:6208:b737 with SMTP id 5614622812f47-3eae4f3bce5mr2757240b6e.17.1733239981545; Tue, 03 Dec 2024 07:33:01 -0800 (PST) Received: from localhost.localdomain ([130.250.255.163]) by smtp.gmail.com with ESMTPSA id 5614622812f47-3ea86036cbbsm2891878b6e.8.2024.12.03.07.33.00 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Tue, 03 Dec 2024 07:33:00 -0800 (PST) From: Jens Axboe To: linux-mm@kvack.org, linux-fsdevel@vger.kernel.org Cc: hannes@cmpxchg.org, clm@meta.com, linux-kernel@vger.kernel.org, willy@infradead.org, kirill@shutemov.name, bfoster@redhat.com, Jens Axboe Subject: [PATCH 11/12] mm/filemap: make buffered writes work with RWF_UNCACHED Date: Tue, 3 Dec 2024 08:31:47 -0700 Message-ID: <20241203153232.92224-13-axboe@kernel.dk> X-Mailer: git-send-email 2.45.2 In-Reply-To: <20241203153232.92224-2-axboe@kernel.dk> References: <20241203153232.92224-2-axboe@kernel.dk> Precedence: bulk X-Mailing-List: linux-fsdevel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 If RWF_UNCACHED is set for a write, mark new folios being written with uncached. This is done by passing in the fact that it's an uncached write through the folio pointer. We can only get there when IOCB_UNCACHED was allowed, which can only happen if the file system opts in. Opting in means they need to check for the LSB in the folio pointer to know if it's an uncached write or not. If it is, then FGP_UNCACHED should be used if creating new folios is necessary. Uncached writes will drop any folios they create upon writeback completion, but leave folios that may exist in that range alone. Since ->write_begin() doesn't currently take any flags, and to avoid needing to change the callback kernel wide, use the foliop being passed in to ->write_begin() to signal if this is an uncached write or not. File systems can then use that to mark newly created folios as uncached. This provides similar benefits to using RWF_UNCACHED with reads. Testing buffered writes on 32 files: writing bs 65536, uncached 0 1s: 196035MB/sec 2s: 132308MB/sec 3s: 132438MB/sec 4s: 116528MB/sec 5s: 103898MB/sec 6s: 108893MB/sec 7s: 99678MB/sec 8s: 106545MB/sec 9s: 106826MB/sec 10s: 101544MB/sec 11s: 111044MB/sec 12s: 124257MB/sec 13s: 116031MB/sec 14s: 114540MB/sec 15s: 115011MB/sec 16s: 115260MB/sec 17s: 116068MB/sec 18s: 116096MB/sec where it's quite obvious where the page cache filled, and performance dropped from to about half of where it started, settling in at around 115GB/sec. Meanwhile, 32 kswapds were running full steam trying to reclaim pages. Running the same test with uncached buffered writes: writing bs 65536, uncached 1 1s: 198974MB/sec 2s: 189618MB/sec 3s: 193601MB/sec 4s: 188582MB/sec 5s: 193487MB/sec 6s: 188341MB/sec 7s: 194325MB/sec 8s: 188114MB/sec 9s: 192740MB/sec 10s: 189206MB/sec 11s: 193442MB/sec 12s: 189659MB/sec 13s: 191732MB/sec 14s: 190701MB/sec 15s: 191789MB/sec 16s: 191259MB/sec 17s: 190613MB/sec 18s: 191951MB/sec and the behavior is fully predictable, performing the same throughout even after the page cache would otherwise have fully filled with dirty data. It's also about 65% faster, and using half the CPU of the system compared to the normal buffered write. Signed-off-by: Jens Axboe --- include/linux/fs.h | 5 +++++ include/linux/pagemap.h | 9 +++++++++ mm/filemap.c | 12 +++++++++++- 3 files changed, 25 insertions(+), 1 deletion(-) diff --git a/include/linux/fs.h b/include/linux/fs.h index 40383f5cc6a2..32255473f79d 100644 --- a/include/linux/fs.h +++ b/include/linux/fs.h @@ -2912,6 +2912,11 @@ static inline ssize_t generic_write_sync(struct kiocb *iocb, ssize_t count) (iocb->ki_flags & IOCB_SYNC) ? 0 : 1); if (ret) return ret; + } else if (iocb->ki_flags & IOCB_UNCACHED) { + struct address_space *mapping = iocb->ki_filp->f_mapping; + + filemap_fdatawrite_range_kick(mapping, iocb->ki_pos, + iocb->ki_pos + count); } return count; diff --git a/include/linux/pagemap.h b/include/linux/pagemap.h index f2d49dccb7c1..e49587c40157 100644 --- a/include/linux/pagemap.h +++ b/include/linux/pagemap.h @@ -14,6 +14,7 @@ #include #include #include /* for in_interrupt() */ +#include #include struct folio_batch; @@ -70,6 +71,14 @@ static inline int filemap_write_and_wait(struct address_space *mapping) return filemap_write_and_wait_range(mapping, 0, LLONG_MAX); } +/* + * Value passed in to ->write_begin() if IOCB_UNCACHED is set for the write, + * and the ->write_begin() handler on a file system supporting FOP_UNCACHED + * must check for this and pass FGP_UNCACHED for folio creation. + */ +#define foliop_uncached ((struct folio *) 0xfee1c001) +#define foliop_is_uncached(foliop) (*(foliop) == foliop_uncached) + /** * filemap_set_wb_err - set a writeback error on an address_space * @mapping: mapping in which to set writeback error diff --git a/mm/filemap.c b/mm/filemap.c index 826df99e294f..00f3c6c58629 100644 --- a/mm/filemap.c +++ b/mm/filemap.c @@ -4095,7 +4095,7 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i) ssize_t written = 0; do { - struct folio *folio; + struct folio *folio = NULL; size_t offset; /* Offset into folio */ size_t bytes; /* Bytes to write to folio */ size_t copied; /* Bytes copied from user */ @@ -4123,6 +4123,16 @@ ssize_t generic_perform_write(struct kiocb *iocb, struct iov_iter *i) break; } + /* + * If IOCB_UNCACHED is set here, we now the file system + * supports it. And hence it'll know to check folip for being + * set to this magic value. If so, it's an uncached write. + * Whenever ->write_begin() changes prototypes again, this + * can go away and just pass iocb or iocb flags. + */ + if (iocb->ki_flags & IOCB_UNCACHED) + folio = foliop_uncached; + status = a_ops->write_begin(file, mapping, pos, bytes, &folio, &fsdata); if (unlikely(status < 0))