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Thu, 16 Jan 2020 17:24:37 -0800 (PST) Received: from [192.168.43.54] ([109.126.145.157]) by smtp.gmail.com with ESMTPSA id s2sm11459145lji.53.2020.01.16.17.24.35 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 16 Jan 2020 17:24:36 -0800 (PST) Subject: Re: [PATCH] fs: optimise kiocb_set_rw_flags() To: Matthew Wilcox Cc: Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org References: <7d493d4872b75fc59556a63ee62c43b30c661ff9.1579223790.git.asml.silence@gmail.com> <20200117012123.GA9226@bombadil.infradead.org> From: Pavel Begunkov Autocrypt: addr=asml.silence@gmail.com; prefer-encrypt=mutual; keydata= mQINBFmKBOQBEAC76ZFxLAKpDw0bKQ8CEiYJRGn8MHTUhURL02/7n1t0HkKQx2K1fCXClbps bdwSHrhOWdW61pmfMbDYbTj6ZvGRvhoLWfGkzujB2wjNcbNTXIoOzJEGISHaPf6E2IQx1ik9 6uqVkK1OMb7qRvKH0i7HYP4WJzYbEWVyLiAxUj611mC9tgd73oqZ2pLYzGTqF2j6a/obaqha +hXuWTvpDQXqcOZJXIW43atprH03G1tQs7VwR21Q1eq6Yvy2ESLdc38EqCszBfQRMmKy+cfp W3U9Mb1w0L680pXrONcnlDBCN7/sghGeMHjGKfNANjPc+0hzz3rApPxpoE7HC1uRiwC4et83 CKnncH1l7zgeBT9Oa3qEiBlaa1ZCBqrA4dY+z5fWJYjMpwI1SNp37RtF8fKXbKQg+JuUjAa9 Y6oXeyEvDHMyJYMcinl6xCqCBAXPHnHmawkMMgjr3BBRzODmMr+CPVvnYe7BFYfoajzqzq+h EyXSl3aBf0IDPTqSUrhbmjj5OEOYgRW5p+mdYtY1cXeK8copmd+fd/eTkghok5li58AojCba jRjp7zVOLOjDlpxxiKhuFmpV4yWNh5JJaTbwCRSd04sCcDNlJj+TehTr+o1QiORzc2t+N5iJ NbILft19Izdn8U39T5oWiynqa1qCLgbuFtnYx1HlUq/HvAm+kwARAQABtDFQYXZlbCBCZWd1 bmtvdiAoc2lsZW5jZSkgPGFzbWwuc2lsZW5jZUBnbWFpbC5jb20+iQJOBBMBCAA4FiEE+6Ju PTjTbx479o3OWt5b1Glr+6UFAlmKBOQCGwMFCwkIBwIGFQgJCgsCBBYCAwECHgECF4AACgkQ Wt5b1Glr+6WxZA//QueaKHzgdnOikJ7NA/Vq8FmhRlwgtP0+E+w93kL+ZGLzS/cUCIjn2f4Q Mcutj2Neg0CcYPX3b2nJiKr5Vn0rjJ/suiaOa1h1KzyNTOmxnsqE5fmxOf6C6x+NKE18I5Jy xzLQoktbdDVA7JfB1itt6iWSNoOTVcvFyvfe5ggy6FSCcP+m1RlR58XxVLH+qlAvxxOeEr/e aQfUzrs7gqdSd9zQGEZo0jtuBiB7k98t9y0oC9Jz0PJdvaj1NZUgtXG9pEtww3LdeXP/TkFl HBSxVflzeoFaj4UAuy8+uve7ya/ECNCc8kk0VYaEjoVrzJcYdKP583iRhOLlZA6HEmn/+Gh9 4orG67HNiJlbFiW3whxGizWsrtFNLsSP1YrEReYk9j1SoUHHzsu+ZtNfKuHIhK0sU07G1OPN 2rDLlzUWR9Jc22INAkhVHOogOcc5ajMGhgWcBJMLCoi219HlX69LIDu3Y34uIg9QPZIC2jwr 24W0kxmK6avJr7+n4o8m6sOJvhlumSp5TSNhRiKvAHB1I2JB8Q1yZCIPzx+w1ALxuoWiCdwV M/azguU42R17IuBzK0S3hPjXpEi2sK/k4pEPnHVUv9Cu09HCNnd6BRfFGjo8M9kZvw360gC1 reeMdqGjwQ68o9x0R7NBRrtUOh48TDLXCANAg97wjPoy37dQE7e5Ag0EWYoE5AEQAMWS+aBV IJtCjwtfCOV98NamFpDEjBMrCAfLm7wZlmXy5I6o7nzzCxEw06P2rhzp1hIqkaab1kHySU7g dkpjmQ7Jjlrf6KdMP87mC/Hx4+zgVCkTQCKkIxNE76Ff3O9uTvkWCspSh9J0qPYyCaVta2D1 Sq5HZ8WFcap71iVO1f2/FEHKJNz/YTSOS/W7dxJdXl2eoj3gYX2UZNfoaVv8OXKaWslZlgqN jSg9wsTv1K73AnQKt4fFhscN9YFxhtgD/SQuOldE5Ws4UlJoaFX/yCoJL3ky2kC0WFngzwRF Yo6u/KON/o28yyP+alYRMBrN0Dm60FuVSIFafSqXoJTIjSZ6olbEoT0u17Rag8BxnxryMrgR dkccq272MaSS0eOC9K2rtvxzddohRFPcy/8bkX+t2iukTDz75KSTKO+chce62Xxdg62dpkZX xK+HeDCZ7gRNZvAbDETr6XI63hPKi891GeZqvqQVYR8e+V2725w+H1iv3THiB1tx4L2bXZDI DtMKQ5D2RvCHNdPNcZeldEoJwKoA60yg6tuUquvsLvfCwtrmVI2rL2djYxRfGNmFMrUDN1Xq F3xozA91q3iZd9OYi9G+M/OA01husBdcIzj1hu0aL+MGg4Gqk6XwjoSxVd4YT41kTU7Kk+/I 5/Nf+i88ULt6HanBYcY/+Daeo/XFABEBAAGJAjYEGAEIACAWIQT7om49ONNvHjv2jc5a3lvU aWv7pQUCWYoE5AIbDAAKCRBa3lvUaWv7pfmcEACKTRQ28b1y5ztKuLdLr79+T+LwZKHjX++P 4wKjEOECCcB6KCv3hP+J2GCXDOPZvdg/ZYZafqP68Yy8AZqkfa4qPYHmIdpODtRzZSL48kM8 LRzV8Rl7J3ItvzdBRxf4T/Zseu5U6ELiQdCUkPGsJcPIJkgPjO2ROG/ZtYa9DvnShNWPlp+R uPwPccEQPWO/NP4fJl2zwC6byjljZhW5kxYswGMLBwb5cDUZAisIukyAa8Xshdan6C2RZcNs rB3L7vsg/R8UCehxOH0C+NypG2GqjVejNZsc7bgV49EOVltS+GmGyY+moIzxsuLmT93rqyII 5rSbbcTLe6KBYcs24XEoo49Zm9oDA3jYvNpeYD8rDcnNbuZh9kTgBwFN41JHOPv0W2FEEWqe JsCwQdcOQ56rtezdCJUYmRAt3BsfjN3Jn3N6rpodi4Dkdli8HylM5iq4ooeb5VkQ7UZxbCWt UVMKkOCdFhutRmYp0mbv2e87IK4erwNHQRkHUkzbsuym8RVpAZbLzLPIYK/J3RTErL6Z99N2 m3J6pjwSJY/zNwuFPs9zGEnRO4g0BUbwGdbuvDzaq6/3OJLKohr5eLXNU3JkT+3HezydWm3W OPhauth7W0db74Qd49HXK0xe/aPrK+Cp+kU1HRactyNtF8jZQbhMCC8vMGukZtWaAwpjWiiH bA== Message-ID: <8cecd243-38aa-292d-15cd-49b485f9253f@gmail.com> Date: Fri, 17 Jan 2020 04:23:55 +0300 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:68.0) Gecko/20100101 Thunderbird/68.3.0 MIME-Version: 1.0 In-Reply-To: <20200117012123.GA9226@bombadil.infradead.org> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="z25OKxZY3gL4n82P5hoaAq2IkX4AunVHc" Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org This is an OpenPGP/MIME signed message (RFC 4880 and 3156) --z25OKxZY3gL4n82P5hoaAq2IkX4AunVHc Content-Type: multipart/mixed; boundary="LjIWb8WWfCwl2iU753V9YLMquf9pCeF9w"; protected-headers="v1" From: Pavel Begunkov To: Matthew Wilcox Cc: Alexander Viro , linux-fsdevel@vger.kernel.org, linux-kernel@vger.kernel.org Message-ID: <8cecd243-38aa-292d-15cd-49b485f9253f@gmail.com> Subject: Re: [PATCH] fs: optimise kiocb_set_rw_flags() References: <7d493d4872b75fc59556a63ee62c43b30c661ff9.1579223790.git.asml.silence@gmail.com> <20200117012123.GA9226@bombadil.infradead.org> In-Reply-To: <20200117012123.GA9226@bombadil.infradead.org> --LjIWb8WWfCwl2iU753V9YLMquf9pCeF9w Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable On 17/01/2020 04:21, Matthew Wilcox wrote: > On Fri, Jan 17, 2020 at 04:16:41AM +0300, Pavel Begunkov wrote: >> kiocb_set_rw_flags() generates a poor code with several memory writes >> and a lot of jumps. Help compilers to optimise it. >> >> Tested with gcc 9.2 on x64-86, and as a result, it its output now is a= >> plain code without jumps accumulating in a register before a memory >> write. >=20 > Nice! >=20 >> static inline int kiocb_set_rw_flags(struct kiocb *ki, rwf_t flags) >> { >> + int kiocb_flags =3D 0; >> + >> if (unlikely(flags & ~RWF_SUPPORTED)) >> return -EOPNOTSUPP; >> =20 >> if (flags & RWF_NOWAIT) { >> if (!(ki->ki_filp->f_mode & FMODE_NOWAIT)) >> return -EOPNOTSUPP; >> - ki->ki_flags |=3D IOCB_NOWAIT; >> + kiocb_flags |=3D IOCB_NOWAIT; >> } >> if (flags & RWF_HIPRI) >> - ki->ki_flags |=3D IOCB_HIPRI; >> + kiocb_flags |=3D IOCB_HIPRI; >> if (flags & RWF_DSYNC) >> - ki->ki_flags |=3D IOCB_DSYNC; >> + kiocb_flags |=3D IOCB_DSYNC; >> if (flags & RWF_SYNC) >> - ki->ki_flags |=3D (IOCB_DSYNC | IOCB_SYNC); >> + kiocb_flags |=3D (IOCB_DSYNC | IOCB_SYNC); >> if (flags & RWF_APPEND) >> - ki->ki_flags |=3D IOCB_APPEND; >> + kiocb_flags |=3D IOCB_APPEND; >> + >> + if (kiocb_flags) >> + ki->ki_flags |=3D kiocb_flags; >> return 0; >> } >=20 > Might it generate even better code to do ... Good idea, thanks! I'll resend >=20 > int kiocb_flags =3D 0; > =20 > + if (!flags) > + return 0; > if (unlikely(flags & ~RWF_SUPPORTED)) > return -EOPNOTSUPP; > =20 > ... >=20 > - if (kiocb_flags) > - ki->ki_flags |=3D kiocb_flags; > + ki->ki_flags |=3D kiocb_flags; >=20 --=20 Pavel Begunkov --LjIWb8WWfCwl2iU753V9YLMquf9pCeF9w-- --z25OKxZY3gL4n82P5hoaAq2IkX4AunVHc Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEE+6JuPTjTbx479o3OWt5b1Glr+6UFAl4hDLUACgkQWt5b1Glr +6Wm3A//aDJGM3s1upPd3JYSDCGp46ZsB3TNq4qJGEaGJsycGT46ZbXllqareMc2 5BBDIKAD8e4hqi/I0vM5jDLB1gmPCWuO5ktOWfI86m0jQfzCjNho64VZd2rmnf2y fANkTryj3a7Nay9ClR6LjCm3C54orILRUi3gn15S1v7+2THVVg5Dh/6W29lCtplC UXlGed/72+y8fxbY2tYmHTx6yRTJigMIBFqe+kYqoWItvvMwRuJHBHoty1PwvXaz INXqzKmWelMmzaCbBMfso9NJv0s8g3XT51BF81BrgErf8M77Wj1ybem+VFprk+uY wzIsl8HxC82Z1Q3/F/+kebtfKXL9pxphfgP2xocSb0ewjtE1QHMRxgrZRFFf4lVI KfVlSE2LhQtjTroeqLJqiAtsUXOqKhXl68HRXfoKYDTqmvYWDE8r1F1G8kjM/Hnj zv0AsP2uZIpgk8H3lxTG35PgsYcccEcNR97lQDIWj/NhHxNx4z+6MSp0wdK/IV4H Q+4HtuFsJQUOlHe/QfNs315Y1G4M8oqWqqpsBfpuUf+fP4oC87Ihyix58/5lZOMk 9Zgoo6IiT/j4BDeeBgINJmT28aqaeJt76TW3Xl3vhTdogb8LvvaMTfjRQ/ABXFym Zj0J1gWL+dGlJiFaD2D8uBHLVfP/JFeZ0WX4YuPMxWW/8m4Afy0= =BWZu -----END PGP SIGNATURE----- --z25OKxZY3gL4n82P5hoaAq2IkX4AunVHc--