From owner-freebsd-hackers@freebsd.org Tue Jan 22 09:32:22 2019 Return-Path: Delivered-To: freebsd-hackers@mailman.ysv.freebsd.org Received: from mx1.freebsd.org (mx1.freebsd.org [IPv6:2610:1c1:1:606c::19:1]) by mailman.ysv.freebsd.org (Postfix) with ESMTP id BCCFE14B5C26; Tue, 22 Jan 2019 09:32:22 +0000 (UTC) (envelope-from shreyankfbsd@gmail.com) Received: from mail-yb1-xb36.google.com (mail-yb1-xb36.google.com [IPv6:2607:f8b0:4864:20::b36]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (Client CN "smtp.gmail.com", Issuer "Google Internet Authority G3" (verified OK)) by mx1.freebsd.org (Postfix) with ESMTPS id 94F7A8307E; Tue, 22 Jan 2019 09:32:21 +0000 (UTC) (envelope-from shreyankfbsd@gmail.com) Received: by mail-yb1-xb36.google.com with SMTP id y7so8249704ybg.13; Tue, 22 Jan 2019 01:32:21 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20161025; h=mime-version:from:date:message-id:subject:to:cc; bh=50N+nEgDiRPbL/DP3FElDMi+xWaSrMEkL1zKIznrOqE=; b=pDzZphqLyZ2neIRxZOOvVoJTG8G+8D3YtIALlqUFFisrPli4O771sOlogA118MO7PH c9GNE+EPgX0VKc89tF1JchxzF3lkPLHRJwOPDJTlpB3yUY22OqfyV04hDyP7Y+3qppQW 9DkNybX501/kyPQJ2UzYhn/cdh9uGsVhpOSMTdeJ2H05M4vXXlMNBu5pyOArgN+Az1h6 hHTVzxVk1CNNTauHMLP3O0/Xj+uspxkZkc1YXIw+lx0mN02Lca0hBPLoO6876A4eQu94 BrN9aSGbsT9dG/akkx7r1Lja7u+Br5pFnpSBa4uWDB2kluqtu+MHAKaJINmHL8Kq1FJP V/BA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:from:date:message-id:subject:to:cc; bh=50N+nEgDiRPbL/DP3FElDMi+xWaSrMEkL1zKIznrOqE=; b=UxLACAaGQOzqBZIzkMy1XE5ZVRWBwy9dbPr46ZyTrchRT5y8SGnH+t+GJMDEouOLel Zy0mXXK3ACsKBUBXkfGCXSzCyoziyJU/OPf+jbDoYtnWguRjBXwbrf10CWxqNSqx4PWH OAoy3Lu9pxztpdxnRJDqlKD0g0iCEFQRB5luLJwq+LVlOiTWicVwL75f9EFlhic5dXWY tGB5JWhdY/cEpgIbByMV6y29LP0r7eN+FtftgAUctQxz6xkk5cM5PI7E9F3Eu9X3oUjK lNOxjBa7PYWodqWkm0MuXWG2aKP9vKkCWGiH6TeGKRfkD+OAAkw2V85B/SlZE+4vveXp 2DPA== X-Gm-Message-State: AJcUukdM9PxrcweARjmqeiayt0h7WQV2mbCUb4GrXAqqeFvivj7zpMl/ 6x8r3FbLyh5xbYAZGZdzOcZhLCggQxj9jbP5v5C1 X-Google-Smtp-Source: ALg8bN7yTeGKJ8bWFvJ4Gv1nhBnvYXurUTKD0DrdNzSJSOG6F4YsED+bs/wk6tRY1BwdCtWOqLs8kDCAOOG7ZrnP4lM= X-Received: by 2002:a25:8209:: with SMTP id q9mr20266506ybk.21.1548149540897; Tue, 22 Jan 2019 01:32:20 -0800 (PST) MIME-Version: 1.0 From: shreyank amartya Date: Tue, 22 Jan 2019 15:02:09 +0530 Message-ID: Subject: PCIe device performance To: freebsd-hackers@freebsd.org Cc: freebsd-drivers@freebsd.org X-Rspamd-Queue-Id: 94F7A8307E X-Spamd-Bar: ------ Authentication-Results: mx1.freebsd.org; dkim=pass header.d=gmail.com header.s=20161025 header.b=pDzZphqL; dmarc=pass (policy=none) header.from=gmail.com; spf=pass (mx1.freebsd.org: domain of shreyankfbsd@gmail.com designates 2607:f8b0:4864:20::b36 as permitted sender) smtp.mailfrom=shreyankfbsd@gmail.com X-Spamd-Result: default: False [-6.37 / 15.00]; ARC_NA(0.00)[]; NEURAL_HAM_MEDIUM(-1.00)[-0.995,0]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20161025]; FROM_HAS_DN(0.00)[]; R_SPF_ALLOW(-0.20)[+ip6:2607:f8b0:4000::/36]; FREEMAIL_FROM(0.00)[gmail.com]; MIME_GOOD(-0.10)[multipart/alternative,text/plain]; TO_DN_NONE(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; TO_MATCH_ENVRCPT_ALL(0.00)[]; RCVD_TLS_LAST(0.00)[]; DKIM_TRACE(0.00)[gmail.com:+]; RCPT_COUNT_TWO(0.00)[2]; DMARC_POLICY_ALLOW(-0.50)[gmail.com,none]; MX_GOOD(-0.01)[cached: alt3.gmail-smtp-in.l.google.com]; RCVD_IN_DNSWL_NONE(0.00)[6.3.b.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.4.6.8.4.0.b.8.f.7.0.6.2.list.dnswl.org : 127.0.5.0]; NEURAL_HAM_SHORT(-0.55)[-0.555,0]; FROM_EQ_ENVFROM(0.00)[]; MIME_TRACE(0.00)[0:+,1:+]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:15169, ipnet:2607:f8b0::/32, country:US]; RCVD_COUNT_TWO(0.00)[2]; IP_SCORE(-2.81)[ip: (-9.62), ipnet: 2607:f8b0::/32(-2.46), asn: 15169(-1.88), country: US(-0.08)]; DWL_DNSWL_NONE(0.00)[gmail.com.dwl.dnswl.org : 127.0.5.0] Content-Type: text/plain; charset="UTF-8" X-Content-Filtered-By: Mailman/MimeDel 2.1.29 X-BeenThere: freebsd-hackers@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Technical Discussions relating to FreeBSD List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 22 Jan 2019 09:32:23 -0000 Hi, I have a PCIe device BAR mapped to a particular region in KVA. I use memcpy to write into that region and measure the transfer rate. Recently, I was able to increase the transfer rate by setting the memory attribute of the BAR mapped region to VM_MEMATTR_WRITE_COMBINING. However, the transfer rate fluctuates wildly and I cannot get a deterministic value. What could be the cause for this? Thanks Shreyank Amartya