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Wed, 4 Sep 2019 08:43:45 +0000 (UTC) Subject: Re: [LKP] [drm/mgag200] 90f479ae51: vm-scalability.median -18.8% regression To: Feng Tang , Daniel Vetter Cc: Stephen Rothwell , Rong Chen , =?UTF-8?Q?Michel_D=c3=a4nzer?= , Linux Kernel Mailing List , dri-devel , LKP References: <64d41701-55a4-e526-17ae-8936de4bc1ef@suse.de> <20190824051605.GA63850@shbuild999.sh.intel.com> <1b897bfe-fd40-3ae3-d867-424d1fc08c44@suse.de> <44029e80-ba00-8246-dec0-fda122d53f5e@suse.de> <90e78ce8-d46a-5154-c324-a05aa1743c98@intel.com> <2e1b4d65-d477-f571-845d-fa0a670859af@suse.de> <20190904062716.GC5541@shbuild999.sh.intel.com> <72c33bf1-9184-e24a-c084-26d9c8b6f9b7@suse.de> <20190904083558.GD5541@shbuild999.sh.intel.com> From: Thomas Zimmermann Openpgp: preference=signencrypt Autocrypt: addr=tzimmermann@suse.de; keydata= xsBNBFs50uABCADEHPidWt974CaxBVbrIBwqcq/WURinJ3+2WlIrKWspiP83vfZKaXhFYsdg XH47fDVbPPj+d6tQrw5lPQCyqjwrCPYnq3WlIBnGPJ4/jreTL6V+qfKRDlGLWFjZcsrPJGE0 BeB5BbqP5erN1qylK9i3gPoQjXGhpBpQYwRrEyQyjuvk+Ev0K1Jc5tVDeJAuau3TGNgah4Yc hdHm3bkPjz9EErV85RwvImQ1dptvx6s7xzwXTgGAsaYZsL8WCwDaTuqFa1d1jjlaxg6+tZsB 9GluwvIhSezPgnEmimZDkGnZRRSFiGP8yjqTjjWuf0bSj5rUnTGiyLyRZRNGcXmu6hjlABEB AAHNKFRob21hcyBaaW1tZXJtYW5uIDx0emltbWVybWFubkBzdXNlLmNvbT7CwJQEEwEIAD4W IQRyF/usjOnPY0ShaOVoDcEdUwt6IwUCWznTtgIbAwUJA8JnAAULCQgHAgYVCgkICwIEFgID AQIeAQIXgAAKCRBoDcEdUwt6I7D7CACBK42XW+7mCiK8ioXMEy1NzGbXC51RzGea8N83oEJS 1KVUtQxrkDxgrW/WLSl/TfqHFsJpdEFOv1XubWbleun3uKPy0e5vZCd5UjZPkeNjnqfCYTDy hVVsdOuFbtWDppJyJrThLqr9AgSFmoCNNUt1SVpYEEOLNE6C32BhlnSq21VLC+YXTgO/ZHTa YXkq54hHj63jwrcjkBSCkXLh37kHeqnl++GHpN+3R+o3w2OpwHAlvVjdKPT27v1tVkiydsFG 65Vd0n3m/ft+IOrGgxQM1C20uqKvsZGB4r3OGR50ekAybO7sjEJJ1Obl4ge/6RRqcvKz4LMb tGs85D6tPIeFzsBNBFs50uABCADGJj+DP1fk+UWOWrf4O61HTbC4Vr9QD2K4fUUHnzg2B6zU R1BPXqLGG0+lzK8kfYU/F5RjmEcClsIkAaFkg4kzKP14tvY1J5+AV3yNqcdg018HNtiyrSwI E0Yz/qm1Ot2NMZ0DdvVBg22IMsiudQ1tx9CH9mtyTbIXgACvl3PW2o9CxiHPE/bohFhwZwh/ kXYYAE51lhinQ3oFEeQZA3w4OTvxSEspiQR8dg8qJJb+YOAc5IKk6sJmmM7JfFMWSr22satM 23oQ3WvJb4RV6HTRTAIEyyZS7g2DhiytgMG60t0qdABG5KXSQW+OKlZRpuWwKWaLh3if/p/u 69dvpanbABEBAAHCwHwEGAEIACYWIQRyF/usjOnPY0ShaOVoDcEdUwt6IwUCWznS4AIbDAUJ A8JnAAAKCRBoDcEdUwt6I6X3CACJ8D+TpXBCqJE5xwog08+Dp8uBpx0T9n1wE0GQisZruACW NofYn8PTX9k4wmegDLwt7YQDdKxQ4+eTfZeLNQqWg6OCftH5Kx7sjWnJ09tOgniVdROzWJ7c VJ/i0okazncsJ+nq48UYvRGE1Swh3A4QRIyphWX4OADOBmTFl9ZYNPnh23eaC9WrNvFr7yP7 iGjMlfEW8l6Lda//EC5VpXVNza0xeae0zFNst2R9pn+bLkihwDLWxOIyifGRxTqNxoS4I1aw VhxPSVztPMSpIA/sOr/N/p6JrBLn+gui2K6mP7bGb8hF+szfArYqz3T1rv1VzUWAJf5Wre5U iNx9uqqx Message-ID: <33d3ce15-6221-bd96-3f26-b710e4da6b1a@suse.de> Date: Wed, 4 Sep 2019 10:43:40 +0200 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.8.0 MIME-Version: 1.0 In-Reply-To: <20190904083558.GD5541@shbuild999.sh.intel.com> Content-Type: multipart/signed; micalg=pgp-sha256; protocol="application/pgp-signature"; boundary="z5u8L7PhZwl2omekefWdTSnCrm327WPWo" 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) --z5u8L7PhZwl2omekefWdTSnCrm327WPWo Content-Type: multipart/mixed; boundary="GAqvzYwfBSRNT5wxc8MZTQlopx9rsHEt8"; protected-headers="v1" From: Thomas Zimmermann To: Feng Tang , Daniel Vetter Cc: Stephen Rothwell , Rong Chen , =?UTF-8?Q?Michel_D=c3=a4nzer?= , Linux Kernel Mailing List , dri-devel , LKP Message-ID: <33d3ce15-6221-bd96-3f26-b710e4da6b1a@suse.de> Subject: Re: [LKP] [drm/mgag200] 90f479ae51: vm-scalability.median -18.8% regression References: <64d41701-55a4-e526-17ae-8936de4bc1ef@suse.de> <20190824051605.GA63850@shbuild999.sh.intel.com> <1b897bfe-fd40-3ae3-d867-424d1fc08c44@suse.de> <44029e80-ba00-8246-dec0-fda122d53f5e@suse.de> <90e78ce8-d46a-5154-c324-a05aa1743c98@intel.com> <2e1b4d65-d477-f571-845d-fa0a670859af@suse.de> <20190904062716.GC5541@shbuild999.sh.intel.com> <72c33bf1-9184-e24a-c084-26d9c8b6f9b7@suse.de> <20190904083558.GD5541@shbuild999.sh.intel.com> In-Reply-To: <20190904083558.GD5541@shbuild999.sh.intel.com> --GAqvzYwfBSRNT5wxc8MZTQlopx9rsHEt8 Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: quoted-printable Hi Am 04.09.19 um 10:35 schrieb Feng Tang: > Hi Daniel, >=20 > On Wed, Sep 04, 2019 at 10:11:11AM +0200, Daniel Vetter wrote: >> On Wed, Sep 4, 2019 at 8:53 AM Thomas Zimmermann = wrote: >>> >>> Hi >>> >>> Am 04.09.19 um 08:27 schrieb Feng Tang: >>>>> Thank you for testing. But don't get too excited, because the patch= >>>>> simulates a bug that was present in the original mgag200 code. A >>>>> significant number of frames are simply skipped. That is apparently= the >>>>> reason why it's faster. >>>> >>>> Thanks for the detailed info, so the original code skips time-consum= ing >>>> work inside atomic context on purpose. Is there any space to optmise= it? >>>> If 2 scheduled update worker are handled at almost same time, can on= e be >>>> skipped? >>> >>> To my knowledge, there's only one instance of the worker. Re-scheduli= ng >>> the worker before a previous instance started, will not create a seco= nd >>> instance. The worker's instance will complete all pending updates. So= in >>> some way, skipping workers already happens. >> >> So I think that the most often fbcon update from atomic context is the= >> blinking cursor. If you disable that one you should be back to the old= >> performance level I think, since just writing to dmesg is from process= >> context, so shouldn't change. >=20 > Hmm, then for the old driver, it should also do the most update in > non-atomic context?=20 >=20 > One other thing is, I profiled that updating a 3MB shadow buffer needs > 20 ms, which transfer to 150 MB/s bandwidth. Could it be related with > the cache setting of DRM shadow buffer? say the orginal code use a > cachable buffer? >=20 >=20 >> >> https://unix.stackexchange.com/questions/3759/how-to-stop-cursor-from-= blinking >> >> Bunch of tricks, but tbh I haven't tested them. >=20 > Thomas has suggested to disable curson by > echo 0 > /sys/devices/virtual/graphics/fbcon/cursor_blink >=20 > We tried that way, and no change for the performance data. There are several ways of disabling the cursor. On my test system, I ente= red tput civis before the test and got better performance. Did you try this as well? Best regards Thomas >=20 > Thanks, > Feng >=20 >> >> In any case, I still strongly advice you don't print anything to dmesg= >> or fbcon while benchmarking, because dmesg/printf are anything but >> fast, especially if a gpu driver is involved. There's some efforts to >> make the dmesg/printk side less painful (untangling the console_lock >> from printk), but fundamentally printing to the gpu from the kernel >> through dmesg/fbcon won't be cheap. It's just not something we >> optimize beyond "make sure it works for emergencies". >> -Daniel >> >>> >>> Best regards >>> Thomas >>> >>>> >>>> Thanks, >>>> Feng >>>> >>>>> >>>>> Best regards >>>>> Thomas >>>> _______________________________________________ >>>> dri-devel mailing list >>>> dri-devel@lists.freedesktop.org >>>> https://lists.freedesktop.org/mailman/listinfo/dri-devel >>>> >>> >>> -- >>> Thomas Zimmermann >>> Graphics Driver Developer >>> SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany >>> GF: Felix Imend=C3=B6rffer, Mary Higgins, Sri Rasiah >>> HRB 21284 (AG N=C3=BCrnberg) >>> >>> _______________________________________________ >>> dri-devel mailing list >>> dri-devel@lists.freedesktop.org >>> https://lists.freedesktop.org/mailman/listinfo/dri-devel >> >> >> >> --=20 >> Daniel Vetter >> Software Engineer, Intel Corporation >> +41 (0) 79 365 57 48 - http://blog.ffwll.ch --=20 Thomas Zimmermann Graphics Driver Developer SUSE Linux GmbH, Maxfeldstrasse 5, 90409 Nuernberg, Germany GF: Felix Imend=C3=B6rffer, Mary Higgins, Sri Rasiah HRB 21284 (AG N=C3=BCrnberg) --GAqvzYwfBSRNT5wxc8MZTQlopx9rsHEt8-- --z5u8L7PhZwl2omekefWdTSnCrm327WPWo Content-Type: application/pgp-signature; name="signature.asc" Content-Description: OpenPGP digital signature Content-Disposition: attachment; filename="signature.asc" -----BEGIN PGP SIGNATURE----- iQEzBAEBCAAdFiEEchf7rIzpz2NEoWjlaA3BHVMLeiMFAl1veTwACgkQaA3BHVML eiN7CAf/SM9JDoFBaUDWj8xO1i+O4qpKpzL0OAfmSuxHySqrhdIuIozl8XbP1KFF SQ2dZWkFxTaR01c4dp8C1bwbYNejR6LapZKzQKIlzKSYdXIbtUPeG8cFV6IfFELl bTWa6NW2c6oWQVHwOwXpKlKqtEBG7Dq7uYNhkavsWjdAOnG68e8jhAyLClvbURRQ XL/pthimnw53eIKHlGgRU+/Ps5KKjMlDZ8hEa3Uuew+oBLeziCfMnqpyUeU5Tp1D riQ+Ogtf0V3VC4VyE43ftY8n/DBXW8y03mkIX5y1lAlldYt9mQDLiTQviWpzVOiW uOg0B9LuCPsEbk09sKs/4ue4Hz7kxQ== =HaY+ -----END PGP SIGNATURE----- --z5u8L7PhZwl2omekefWdTSnCrm327WPWo--