From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from bombadil.infradead.org ([198.137.202.133]:59170 "EHLO bombadil.infradead.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1730144AbfKHJZq (ORCPT ); Fri, 8 Nov 2019 04:25:46 -0500 Date: Fri, 8 Nov 2019 10:25:33 +0100 From: Peter Zijlstra Subject: Re: [RFC PATCH 0/4] Speed booting by sorting ORC unwind tables at build time Message-ID: <20191108092533.GN5671@hirez.programming.kicks-ass.net> References: <20191107143205.206606-1-shile.zhang@linux.alibaba.com> <20191107152244.GD4114@hirez.programming.kicks-ass.net> <85abe498-f241-4752-81b5-6c0314f5a1e8@linux.alibaba.com> <20191108092136.GH4114@hirez.programming.kicks-ass.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20191108092136.GH4114@hirez.programming.kicks-ass.net> Sender: linux-kbuild-owner@vger.kernel.org List-ID: To: Shile Zhang Cc: Masahiro Yamada , Michal Marek , Thomas Gleixner , Ingo Molnar , Borislav Petkov , Josh Poimboeuf , x86@kernel.org, "H . Peter Anvin" , linux-kernel@vger.kernel.org, linux-kbuild@vger.kernel.org On Fri, Nov 08, 2019 at 10:21:36AM +0100, Peter Zijlstra wrote: > On Fri, Nov 08, 2019 at 09:42:55AM +0800, Shile Zhang wrote: > > > > Can sort{ex,orc}table() be ran concurrently? Do they want to be the same > > > (threaded) tool? > > > I think it is possible to do those sort work concurrently, likes deferred > > memory init which is big boot time speed up. > > But I don't know if the exception table and ORC unwind tables can be > > deferred, due to those tables might be used in early boot time, for early > > exception handling and early debugging. I'm not familiar with that. > > I meant at link time, run both sorts concurrently such that we only have > to wait for the longest, instead of the sum of them. > > They're not changing the same part of the ELF file, so it should be > possible to have one tool have multiple threads, each sorting a > different table. > > Aside from the .ex_table and ORC there's also .jump_table that wants > sorting (see jump_label_sort_entries()). Oh, and I'll be adding .static_call_sites soon, see: https://lkml.kernel.org/r/20191007082708.013939311@infradead.org (I should repost that) That gives us 4 tables to sort which we can do concurrently in 4 threads. > I agree that doing it at link time makes sense, I just hate to do all > this sorting in sequence and blowing up the link time. I don't build for > customers, I build for single use boot and linking _SUCKS_.