Received: from malur.postgresql.org ([217.196.149.56]) by arkaria.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jhMpH-00032p-9j for pgsql-hackers@arkaria.postgresql.org; Sat, 06 Jun 2020 00:36:43 +0000 Received: from localhost ([127.0.0.1] helo=malur.postgresql.org) by malur.postgresql.org with esmtp (Exim 4.92) (envelope-from ) id 1jhMpF-0000DU-UK for pgsql-hackers@arkaria.postgresql.org; Sat, 06 Jun 2020 00:36:41 +0000 Received: from magus.postgresql.org ([2a02:c0:301:0:ffff::29]) by malur.postgresql.org with esmtps (TLS1.3:ECDHE_RSA_AES_256_GCM_SHA384:256) (Exim 4.92) (envelope-from ) id 1jhMpF-0000DN-Mt for pgsql-hackers@lists.postgresql.org; Sat, 06 Jun 2020 00:36:41 +0000 Received: from tamriel.snowman.net ([96.255.250.162]) by magus.postgresql.org with esmtp (Exim 4.92) (envelope-from ) id 1jhMp8-0008SQ-O9 for pgsql-hackers@postgresql.org; Sat, 06 Jun 2020 00:36:40 +0000 Received: by tamriel.snowman.net (Postfix, from userid 1000) id AD1385F7A2; Fri, 5 Jun 2020 20:36:32 -0400 (EDT) Date: Fri, 5 Jun 2020 20:36:32 -0400 From: Stephen Frost To: Tomas Vondra Cc: Thomas Munro , Dmitry Dolgov <9erthalion6@gmail.com>, David Steele , Andres Freund , Alvaro Herrera , pgsql-hackers Subject: Re: WIP: WAL prefetch (another approach) Message-ID: <20200606003632.GS6680@tamriel.snowman.net> References: <226b5950-7404-a51d-8dc7-53895b363a38@pgmasters.net> <20200419114820.h62ryte7uwu46e2x@localhost> <20200425191935.4p6qxzzu5bklodwk@localhost> <20200502151423.yf52i63u232fdfrg@localhost> <20200605223422.r76a5rpl2zg2xo34@development> MIME-Version: 1.0 Content-Type: multipart/signed; micalg=pgp-sha512; protocol="application/pgp-signature"; boundary="7vS62bsm3BVGCDKV" Content-Disposition: inline In-Reply-To: <20200605223422.r76a5rpl2zg2xo34@development> User-Agent: Mutt/1.5.24 (2015-08-30) List-Id: List-Help: List-Subscribe: List-Post: List-Owner: List-Archive: Precedence: bulk --7vS62bsm3BVGCDKV Content-Type: text/plain; charset=us-ascii Content-Disposition: inline Greetings, * Tomas Vondra (tomas.vondra@2ndquadrant.com) wrote: > I wonder if we can collect some stats to measure how effective the > prefetching actually is. Ultimately we want something like cache hit > ratio, but we're only preloading into page cache, so we can't easily > measure that. Perhaps we could measure I/O timings in redo, though? That would certainly be interesting, particularly as this optimization seems likely to be useful on some platforms (eg, zfs, where the filesystem block size is larger than ours..) and less on others (traditional systems which have a smaller block size). Thanks, Stephen --7vS62bsm3BVGCDKV Content-Type: application/pgp-signature; name="signature.asc" -----BEGIN PGP SIGNATURE----- Version: GnuPG v1 iQIcBAEBCgAGBQJe2uUQAAoJEO1sijiDR2RVOeQQALPorEetQnx1GmJnBAy+iCg1 juhwPRU2nanADVaTy50RcfbF340lQ8G90FJ5Pva+8rOeH1rnadvHCPAzwuB68+4t UL5qogynNSzpziMDDgr0YH+XvjGEg/3m/g357JAu6Rt4sUOqiUq0HG+4DN6V1vEu g1cD4OqcGs+FX4CDCyDQ5+c+1BSAgk7SIcFhHn2orR+xZq2z6YYUJBJfVx7XdsDh CU3P+kgKUPWv4aWt3ntZCHJYZjgyz3Wru+RcjVIcea3a1M0WN0Eo/BkDLh71FTGC lQDK+CD0gH05djxH0dSf1AJyTFrQCMScsYv36sHK9m//TR0mrtutNCkur8SgcKpC 6qn62DTp96lkCy7k2ynSFHBVFtBkJPACnHwR4pqwEzHCEztH5wc0biQC6gBD0w+C KJScIzKMaoKitftq/2MyzTldXYHEG93VcrxXmgkmVXyEuICI4WLIrGkuTZidVFWj R9sP+xlPqqZ2tR9xjdhetCghAXhyi0zrZFDMGevyHt/N5RRe+pHSpw2wbJko/X+Q DjAL9jxOSNKouXa9XNFODi0lE9t/F3YWcTxvDQOh2q3Ajcb+uYgb02LNPPkWHK8m p9LtpRgPQ/2urQMZJ60AJkalaKTLLWSG40tR0VJdfS2+MzfIIginXljmKiagH1D3 UthjNp+0HbHthcjewdgc =bGpi -----END PGP SIGNATURE----- --7vS62bsm3BVGCDKV--