From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from mail-ej1-f45.google.com (mail-ej1-f45.google.com [209.85.218.45]) (using TLSv1.2 with cipher ECDHE-RSA-AES128-GCM-SHA256 (128/128 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id 075C61B806 for ; Sun, 21 Apr 2024 15:45:51 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=209.85.218.45 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713714353; cv=none; b=dNHx6guHiKxuHIo5yF6xsm8xN94jhlqRuMilJ9y/CkgcHNqc65W4k8YfFOYCSrQT2YAALm3fVlQ4Ue7gRZU0Nx/YAFGxlxRiaZWzqNd6FXjxNK6Pok8PkcCVNISsgUL856Y3W3r7v7k4sUe5x50Jjcc+S34ekSYixTxSH7oFZrI= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1713714353; c=relaxed/simple; bh=bbPF2QEzf+DWbY+ZW15GbZDN77y/WEzEF0orcroKSN0=; h=MIME-Version:References:In-Reply-To:From:Date:Message-ID:Subject: To:Cc:Content-Type; b=imZE1D5v75zl2/LGhLtEIt8xmKvIqtlREZGgPH62cVa/G0usHRVPricf+BNetA4pV2D4OWNeu+9cZkMOcJ/76+j7k0AB2DMX4FAiUNeyJlgYPYxJFhfFjkCjfXN9zyVrB907PSR1+ttBpBTghuQnZ6g1+gUmH8iPfi3dED7Wo40= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com; spf=pass smtp.mailfrom=gmail.com; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b=nkMkT0hn; arc=none smtp.client-ip=209.85.218.45 Authentication-Results: smtp.subspace.kernel.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: smtp.subspace.kernel.org; spf=pass smtp.mailfrom=gmail.com Authentication-Results: smtp.subspace.kernel.org; dkim=pass (2048-bit key) header.d=gmail.com header.i=@gmail.com header.b="nkMkT0hn" Received: by mail-ej1-f45.google.com with SMTP id a640c23a62f3a-a55b0213a0dso46296066b.2 for ; Sun, 21 Apr 2024 08:45:51 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20230601; t=1713714350; x=1714319150; darn=vger.kernel.org; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:from:to:cc:subject:date :message-id:reply-to; bh=0CG3uKISfp8ouFYMkhXdgTfDAYQaKzqX8W6qxFPNd7Q=; b=nkMkT0hnkG8HcC3JnP0mS+Xr8GYCGmMPOHg+rGKUNvl7dzDESE1W8HNAlUto/tLt/z vYlE5k6m7hlJ1D/95LGBc/odSGQWNKvBV2Qlf8fA1foU3zH5UcYtoSI64+UCD/XdTQkI mBeWYeU6HPPYSEbXRDXBaPof5GEogNpV8WHhpgdNlQo7+eHT4JYZGZdrG1EjfiYG1hfw BKNXqny1wUmvTsaDmjHSR2pDc3eY66URjzqkVeAzAgI4I9k8ukKZdfeJDxUJ9uCFcvjp NNAlXX/xFtoEDwGSFObKxODQ93377ggNPF0dzH2CIPUE16epNbuffGtdrto5tSQUV7zV AliA== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20230601; t=1713714350; x=1714319150; h=content-transfer-encoding:cc:to:subject:message-id:date:from :in-reply-to:references:mime-version:x-gm-message-state:from:to:cc :subject:date:message-id:reply-to; bh=0CG3uKISfp8ouFYMkhXdgTfDAYQaKzqX8W6qxFPNd7Q=; b=XDRAsdGdv6wlF2xSMF6Y0MNWEpIY3ir3Y0mVB0lLk1jiX0JHwaSdLokG9a0P82Gff6 3eHET09fqL4MzL5q55ZDIkReWm5DNkjQlTqjs83CmZKSc9CLu29F2qrnla64JAGtJ7Pw 3KR3Yf5YyJs1irGie/FCuez10cHGYxCpZnJ80tg+fuvGjN2XruFUWvd3UMtMkKwEl4+L JwE/ih35KuGcgnKM5KN8zsmKCayS0wjg5JTL4rJ5oDz/4I2HUxfl4+SK/bmTOrBhfU+O eWRqpiAFIR+UDZBmEsV050Gn7s+nd80M/HFktwokePFKVHBGsPdjsLMsDalivbFke/kP C24Q== X-Gm-Message-State: AOJu0YxRdHN7jjIye3TasUEhHfEfFQSqb0Rj7LhSkrIuwp6uBNyfw9gV dL0cvuQOtbmu15obOlTe4dHGgUzW1ACu3lOF6nDUm01tj1TugpqsgnAbSTThkmKTw5quxhLiRv6 RLSp5X+ZLLLZ6j1EV0VQza14N86w= X-Google-Smtp-Source: AGHT+IFOfyDF7ubMBG4n9qfgLzBeoVo3w7VGbXo9Fh1SHgedhJT4Try26yHd579P78alr3Yp5uQ40BK+imN7PJ6UQdE= X-Received: by 2002:a17:906:39c1:b0:a46:3ce4:5acb with SMTP id i1-20020a17090639c100b00a463ce45acbmr5020384eje.75.1713714350038; Sun, 21 Apr 2024 08:45:50 -0700 (PDT) Precedence: bulk X-Mailing-List: git@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 References: <65f32df3f49341bf192b606914d44cc937f7971a.camel@intelfx.name> In-Reply-To: <65f32df3f49341bf192b606914d44cc937f7971a.camel@intelfx.name> From: Mike Castle Date: Sun, 21 Apr 2024 08:45:38 -0700 Message-ID: Subject: Re: Building with PGO: concurrency and test data To: intelfx@intelfx.name Cc: git@vger.kernel.org Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: quoted-printable On Sat, Apr 20, 2024 at 5:53=E2=80=AFPM wrote: > I'm trying to build Git with PGO (for a private distribution) and I > have two questions about the specifics of the profiling process. Generally speaking, there does not need to be a lot of execution to generate good profiles. Execute the happy paths and collect data from those. (Which implies that unittests are usually a bad source of profile data.) Many folks use performance tests to generate profiles because they are already written, but often, they are overkill. Depending on what is going on in the real world, more resources are spent on collecting data than would be saved by the resulting optimizations. I'd say, don't worry about it, and just go with what is already provided. For tools like git, each run is short enough that improvements are not likely to be noticed in day-to-day activities. It is still likely to be IO bound. Most perceived performance issues are more likely to be addressed by algorithmic improvements (in general, not just git), rather than feedback profiles. Now, for any busy long running servers, this can make a bigger difference, particularly for computationally expensive operations like authentication. But again, IO is likely to dominate. mrc