From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io1-f66.google.com ([209.85.166.66]:36624 "EHLO mail-io1-f66.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1726218AbeKGTcq (ORCPT ); Wed, 7 Nov 2018 14:32:46 -0500 Received: by mail-io1-f66.google.com with SMTP id o19-v6so11468883iod.3 for ; Wed, 07 Nov 2018 02:03:08 -0800 (PST) MIME-Version: 1.0 In-Reply-To: <20181106154840.3b448356214afa63dc8cb28c@linux-foundation.org> References: <20181029192521.23059-1-dave@stgolabs.net> <20181106154840.3b448356214afa63dc8cb28c@linux-foundation.org> From: Miklos Szeredi Date: Wed, 7 Nov 2018 11:03:06 +0100 Message-ID: Subject: Re: [PATCH] fs/proc: introduce /proc/stat2 file To: Andrew Morton Cc: Daniel Colascione , Davidlohr Bueso , longman@redhat.com, linux-fsdevel@vger.kernel.org, linux-kernel , Davidlohr Bueso Content-Type: text/plain; charset="UTF-8" Sender: linux-fsdevel-owner@vger.kernel.org List-ID: On Wed, Nov 7, 2018 at 12:48 AM, Andrew Morton wrote: > On Mon, 29 Oct 2018 23:04:45 +0000 Daniel Colascione wrote: > >> On Mon, Oct 29, 2018 at 7:25 PM, Davidlohr Bueso wrote: >> > This patch introduces a new /proc/stat2 file that is identical to the >> > regular 'stat' except that it zeroes all hard irq statistics. The new >> > file is a drop in replacement to stat for users that need performance. >> >> For a while now, I've been thinking over ways to improve the >> performance of collecting various bits of kernel information. I don't >> think that a proliferation of special-purpose named bag-of-fields file >> variants is the right answer, because even if you add a few info-file >> variants, you're still left with a situation where a given file >> provides a particular caller with too little or too much information. >> I'd much rather move to a model in which userspace *explicitly* tells >> the kernel which fields it wants, with the kernel replying with just >> those particular fields, maybe in their raw binary representations. >> The ASCII-text bag-of-everything files would remain available for >> ad-hoc and non-performance critical use, but programs that cared about >> performance would have an efficient bypass. One concrete approach is >> to let users open up today's proc files and, instead of read(2)ing a >> text blob, use an ioctl to retrieve specified and targeted information >> of the sort that would normally be encoded in the text blob. Because >> callers would open the same file when using either the text or binary >> interfaces, little would have to change, and it'd be easy to implement >> fallbacks when a particular system doesn't support a particular >> fast-path ioctl. Please. Sysfs, with the one value per file rule, was created exactly for the purpose of eliminating these sort of problems with procfs. So instead of inventing special purpose interfaces for proc, just make the info available in sysfs, if not already available. Thanks, Miklos