From mboxrd@z Thu Jan 1 00:00:00 1970 From: "Keith Packard" Subject: Re: [PATCH] vulkan: Add VK_EXT_calibrated_timestamps extension (radv and anv) [v4] Date: Tue, 16 Oct 2018 22:14:03 -0700 Message-ID: <87h8hl6tpg.fsf@keithp.com> References: <20181015230515.3695-1-keithp@keithp.com> <20181016053150.11453-1-keithp@keithp.com> <87bm7t8z3k.fsf@keithp.com> <8736t58usr.fsf@keithp.com> <87tvll7dha.fsf@keithp.com> <87r2gp7b6m.fsf@keithp.com> Mime-Version: 1.0 Content-Type: multipart/mixed; boundary="===============1218903923==" Return-path: In-Reply-To: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Errors-To: mesa-dev-bounces@lists.freedesktop.org Sender: "mesa-dev" To: Jason Ekstrand Cc: ML mesa-dev , Maling list - DRI developers List-Id: dri-devel@lists.freedesktop.org --===============1218903923== Content-Type: multipart/signed; boundary="=-=-="; micalg=pgp-sha256; protocol="application/pgp-signature" --=-=-= Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable Jason Ekstrand writes: > Doing all of the CPU sampling on one side or the other of the GPU sampling > would probably reduce our window. True, although as I said, it's taking several =C2=B5s to get through the loop, and the gpu clock tick is far smaller than that, so even adding the two values together to make it fit the current implementation won't make the deviation that much larger. > This leaves us with a delta of I + max(P(M), P(R), P(G)). In > particular, any two real-number valued times are, instantaneously, > within that interval. That, at least, would be easy to compute, and scale nicely if we added more clocks in the future. > Personally, I'm completely content to have the delta just be a the first > one: a bound on the difference between any two real-valued times. At this > point, I can guarantee you that far more thought has been put into this > mesa-dev discussion than was put into the spec and I think we're rapidly > getting to the point of diminishing returns. :-) It seems likely. How about we do the above computation for the current code and leave it at that? =2D-=20 =2Dkeith --=-=-= Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- iQIzBAEBCAAdFiEEw4O3eCVWE9/bQJ2R2yIaaQAAABEFAlvGxRsACgkQ2yIaaQAA ABEjmhAAmmC7EtLYB4PEacjlhjqb8iUKP5sOEe9AevO3B4VpTcYsSvEBjeyCfq1V K6HXYWX2mQ18r+5/+Ji4HVNGIq7o7KZhafnM9O4/JAzRiQS5wyS1xXRPfLbotqFy 8a2R6hTA/qX+fAFhym9jUf92Bk4Yd8mGy/BK0NnD1/fS37OMFL/ThmduBDjYNtk2 Q3uM22zi/mhR1c1Lg0dLfen25juRsDMvnM8XoZivwhMITcJWNBOg0ScZEDlEdZuG REoSB3lVo+u1qcIJRD+WSNUliRtBszX6mEebcqOsPYtdEDBDC8IbdA0oQ8zdiU0r WnDUmM5Jh8u2Wo/IzTE4YjY9VPPYe8PB97LufJI9P8Ys+7LaeRQejRGOnxlWsJ7h Nt5EHheXfS/VXBSk4SyoFTVxapsBz2hnIa4lmHrnW77/9gqru+hAQstipZT2Cfm1 SdSBr/Dx7NkeE73+kE6sLNK7I2GPLUVcU4tKKtLten6MHI1waZ9mqiMZaCvI9pfI E2vCv9juIdyBioXqSEdWcMEMtgHV9G7UBm3bnwKO5zxu4/jSl/NSB3f7yk4+ybTN Zbg2SOQtsAVFxO9Mv+zwwog61Wr88yLbIQtSnuML2AYmuQukF63tc++fX9+i/3JU zZ8yUaGYFrBiAzj1I5yepVOT8Q74rYRLp/ORb9iarB/ng0WDteQ= =9Lz7 -----END PGP SIGNATURE----- --=-=-=-- --===============1218903923== Content-Type: text/plain; charset="utf-8" MIME-Version: 1.0 Content-Transfer-Encoding: base64 Content-Disposition: inline X19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX19fX18KbWVzYS1kZXYg bWFpbGluZyBsaXN0Cm1lc2EtZGV2QGxpc3RzLmZyZWVkZXNrdG9wLm9yZwpodHRwczovL2xpc3Rz LmZyZWVkZXNrdG9wLm9yZy9tYWlsbWFuL2xpc3RpbmZvL21lc2EtZGV2Cg== --===============1218903923==--