From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org X-Spam-Level: X-Spam-Status: No, score=-11.0 required=3.0 tests=BAYES_00,DKIMWL_WL_HIGH, DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,INCLUDES_PATCH,MAILING_LIST_MULTI, SPF_HELO_NONE,SPF_PASS,URIBL_BLOCKED autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 89CD8C433DB for ; Tue, 23 Feb 2021 20:55:38 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [23.128.96.18]) by mail.kernel.org (Postfix) with ESMTP id 435A664E00 for ; Tue, 23 Feb 2021 20:55:38 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S233794AbhBWUzg (ORCPT ); Tue, 23 Feb 2021 15:55:36 -0500 Received: from mail.kernel.org ([198.145.29.99]:48974 "EHLO mail.kernel.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S231594AbhBWUza (ORCPT ); Tue, 23 Feb 2021 15:55:30 -0500 Received: by mail.kernel.org (Postfix) with ESMTPSA id 5C95060233; Tue, 23 Feb 2021 20:54:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=kernel.org; s=k20201202; t=1614113689; bh=2LyNLNXwfUV4cMur0+fcQl9ItS2sdYXeL9Er3zGpzSM=; h=Date:From:To:Cc:Subject:References:In-Reply-To:From; b=VX3ZulvA7TJS70wZCZ9zEz6Dh0GdeI9kbOke0N7bUxwUVyFVEARp/GyDNShhWPOUh 6x1sSOgDe2y0SdzYa2w4o8Q0ycqMmB+OuwyvQxV7GBiHbT9cMPd+71bpTHf9opocoG hX9N0JL+sO2qQeCRkWWMZV7tcMnHhY2fjGc0OD/MfsyGAk6sokkhxC7TVd/gEAR04i STvLbsHATdmnVG6LkL/QLFLIHqJcSZhwuncW8km7j/eHZHHjyrAzfejRBqlPXAtFTk Yhzsop68uxhEWGPOUqr/qoaOKP6nLY8Zpewsv8IwloFSuhquW8BGUau2PmwZf0ivQ/ ZJooXhJFlR0fA== Received: by quaco.ghostprotocols.net (Postfix, from userid 1000) id 299CD40CD9; Tue, 23 Feb 2021 17:54:46 -0300 (-03) Date: Tue, 23 Feb 2021 17:54:46 -0300 From: Arnaldo Carvalho de Melo To: Bill Wendling Cc: dwarves@vger.kernel.org, bpf , Arnaldo Carvalho de Melo Subject: Re: [RFC 0/1] Combining CUs into a single hash table Message-ID: References: <20210212211607.2890660-1-morbo@google.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-Url: http://acmel.wordpress.com Precedence: bulk List-ID: X-Mailing-List: bpf@vger.kernel.org Em Tue, Feb 23, 2021 at 12:44:58PM -0800, Bill Wendling escreveu: > Bump for exposure. While preparing my presentation for devconf.cz I stumbled on a problem with split btf, I want to first bisect this before publishing... I'll move this to the front of my priority list and inform here about it ASAP. - Arnaldo > On Fri, Feb 12, 2021 at 1:16 PM Bill Wendling wrote: > > > > Hey gang, > > > > I would like your feedback on this patch. > > > > This patch creates one hash table that all CUs share. The impetus for this > > patch is to support clang's LTO (Link-Time Optimizations). Currently, pahole > > can't handle the DWARF data that clang produces, because the CUs may refer to > > tags in other CUs (all of the code having been squozen together). > > > > One solution I found is to process the CUs in two steps: > > > > 1. add the CUs into a single hash table, and > > 2. perform the recoding and finalization steps in a a separate step. > > > > The issue I'm facing with this patch is that it balloons the runtime from > > ~11.11s to ~14.27s. It looks like the underlying cause is that some (but not > > all) hash buckets have thousands of entries each. I've bumped up the > > HASHTAGS__BITS from 15 to 16, which helped a little. Bumping it up to 17 or > > above causes a failure. > > > > A couple of things I thought of may help. We could increase the number of > > buckets, which would help with distribution. As I mentioned though, that seemed > > to cause a failure. Another option is to store the bucket entries in a > > non-list, e.g. binary search tree. > > > > I wanted to get your opinions before I trod down one of these roads. > > > > Share and enjoy! > > -bw > > > > Bill Wendling (1): > > dwarf_loader: have all CUs use a single hash table > > > > dwarf_loader.c | 45 +++++++++++++++++++++++++++++++++------------ > > 1 file changed, 33 insertions(+), 12 deletions(-) > > > > -- > > 2.30.0.478.g8a0d178c01-goog > > -- - Arnaldo