From owner-svn-src-head@freebsd.org Fri Dec 7 18:28:57 2018 Return-Path: Delivered-To: svn-src-head@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 9521C1316190; Fri, 7 Dec 2018 18:28:57 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from mail.baldwin.cx (bigwig.baldwin.cx [IPv6:2001:470:1f11:75::1]) (using TLSv1 with cipher DHE-RSA-CAMELLIA256-SHA (256/256 bits)) (Client did not present a certificate) by mx1.freebsd.org (Postfix) with ESMTPS id 358BC719DC; Fri, 7 Dec 2018 18:28:57 +0000 (UTC) (envelope-from jhb@FreeBSD.org) Received: from John-Baldwins-MacBook-Pro-2.local (ralph.baldwin.cx [66.234.199.215]) by mail.baldwin.cx (Postfix) with ESMTPSA id 2054610A87D; Fri, 7 Dec 2018 13:28:55 -0500 (EST) Subject: Re: svn commit: r341682 - head/sys/sys To: Ian Lepore , Mateusz Guzik , src-committers@freebsd.org, svn-src-all@freebsd.org, svn-src-head@freebsd.org References: <201812071205.wB7C5BvA038350@repo.freebsd.org> <1544206201.1860.288.camel@freebsd.org> From: John Baldwin Openpgp: preference=signencrypt Autocrypt: addr=jhb@FreeBSD.org; keydata= xsDiBETQ+XcRBADMFybiq69u+fJRy/0wzqTNS8jFfWaBTs5/OfcV7wWezVmf9sgwn8TW0Dk0 c9MBl0pz+H01dA2ZSGZ5fXlmFIsee1WEzqeJzpiwd/pejPgSzXB9ijbLHZ2/E0jhGBcVy5Yo /Tw5+U/+laeYKu2xb0XPvM0zMNls1ah5OnP9a6Ql6wCgupaoMySb7DXm2LHD1Z9jTsHcAQMD /1jzh2BoHriy/Q2s4KzzjVp/mQO5DSm2z14BvbQRcXU48oAosHA1u3Wrov6LfPY+0U1tG47X 1BGfnQH+rNAaH0livoSBQ0IPI/8WfIW7ub4qV6HYwWKVqkDkqwcpmGNDbz3gfaDht6nsie5Z pcuCcul4M9CW7Md6zzyvktjnbz61BADGDCopfZC4of0Z3Ka0u8Wik6UJOuqShBt1WcFS8ya1 oB4rc4tXfSHyMF63aPUBMxHR5DXeH+EO2edoSwViDMqWk1jTnYza51rbGY+pebLQOVOxAY7k do5Ordl3wklBPMVEPWoZ61SdbcjhHVwaC5zfiskcxj5wwXd2E9qYlBqRg80eSm9obiBCYWxk d2luIDxqb2huQGJhbGR3aW4uY3g+wmMEExECACMCGwMGCwkIBwMCBBUCCAMEFgIDAQIeAQIX gAUCRND5wwIZAQAKCRBy3lIGd+N/BNLXAJ9KIb6teuDL1W+FkCgvv+y8PxKTkACeIUfbn3sl cueBzqTcf09idwa8YTbOwU0ERND5ghAIAPwsO0B7BL+bz8sLlLoQktGxXwXQfS5cInvL17Ds gnr31AKa94j9EnXQyPEj7u0d+LmEe6CGEGDh1OcGFTMVrof2ZzkSy4+FkZwMKJpTiqeaShMh +GojXlwIMDxyADYvBIg3eN5YdFKaPQpfgSqhT+7El7w+wSZZD8pPQuLAnie5iz9C8iKy4/cM SOrHYUK/tO+Nhw8Jjlw94Ik0T80iEhI2t+XBVjwdfjbq3HrJ0ehqdBwukyeJRYKmbn298KOF QVHOEVbHA4rF/37jzaMadK43FgJ0SAhPPF5l4l89z5oPu0b/+5e2inA3b8J3iGZxywjM+Csq 1tqzhltEc7Q+E08AAwUIAL+15XH8bPbjNJdVyg2CMl10JNW2wWg2Q6qdljeaRqeR6zFus7EZ TwtXsNzs5bP8y51PSUDJbeiy2RNCNKWFMndM22TZnk3GNG45nQd4OwYK0RZVrikalmJY5Q6m 7Z164yrZgIXFdKj2t8F+x613/SJW1lIr9/bDp4U9tw0V1g3l2dFtD3p3ZrQ3hpoDtoK70ioI AjjHaIXIAcm3FGZFXy503DOA0KaTWwvOVdYCFLm3zWuSOmrX/GsEc7ovasOWwjPn878qVjbU KWwxQ4QkF4OhUV9zPtf9tDSAZ3x7QSwoKbCoRCZ/xbyTUPyQ1VvNy/mYrBcYlzHodsaqUDjH uW/CSQQYEQIACQUCRND5ggIbDAAKCRBy3lIGd+N/BCO8AJ9j1dWVQWxw/YdTbEyrRKOY8YZN wwCfafMAg8QvmOWnHx3wl8WslCaXaE8= Message-ID: <07a9fd27-3c8f-9ba4-2f3d-17f65c51b2c4@FreeBSD.org> Date: Fri, 7 Dec 2018 10:28:53 -0800 User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.12; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 MIME-Version: 1.0 In-Reply-To: <1544206201.1860.288.camel@freebsd.org> Content-Type: text/plain; charset=utf-8 Content-Language: en-US Content-Transfer-Encoding: 8bit X-Greylist: Sender succeeded SMTP AUTH, not delayed by milter-greylist-4.4.3 (mail.baldwin.cx); Fri, 07 Dec 2018 13:28:55 -0500 (EST) X-Virus-Scanned: clamav-milter 0.99.2 at mail.baldwin.cx X-Virus-Status: Clean X-Rspamd-Queue-Id: 358BC719DC X-Spamd-Result: default: False [-2.92 / 15.00]; local_wl_from(0.00)[FreeBSD.org]; NEURAL_HAM_MEDIUM(-0.99)[-0.995,0]; NEURAL_HAM_SHORT(-0.92)[-0.924,0]; NEURAL_HAM_LONG(-1.00)[-0.999,0]; ASN(0.00)[asn:6939, ipnet:2001:470::/32, country:US] X-Rspamd-Server: mx1.freebsd.org X-BeenThere: svn-src-head@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: SVN commit messages for the src tree for head/-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 07 Dec 2018 18:28:57 -0000 On 12/7/18 10:10 AM, Ian Lepore wrote: > On Fri, 2018-12-07 at 12:05 +0000, Mateusz Guzik wrote: >> Author: mjg >> Date: Fri Dec  7 12:05:11 2018 >> New Revision: 341682 >> URL: https://svnweb.freebsd.org/changeset/base/341682 >> >> Log: >>   unr64: use locked variant if not __LP64__ >>    >>   The current ifdefs are not sufficient to distinguish 32- and 64- >> bit >>   variants, which results e.g. in powerpc64 not using atomics. >>    >>   While some 32-bit archs provide 64-bit atomics, there is no huge >> advantage >>   of using them on these platforms. >>    >>   Reported by: many >>   Suggested by: jhb >>   Sponsored by: The FreeBSD Foundation >> >> Modified: >>   head/sys/sys/systm.h >> >> Modified: head/sys/sys/systm.h >> ===================================================================== >> ========= >> --- head/sys/sys/systm.h Fri Dec  7 12:02:31 2018 (r341 >> 681) >> +++ head/sys/sys/systm.h Fri Dec  7 12:05:11 2018 (r341 >> 682) >> @@ -523,7 +523,7 @@ int alloc_unr_specific(struct unrhdr *uh, u_int >> item); >>  int alloc_unrl(struct unrhdr *uh); >>  void free_unr(struct unrhdr *uh, u_int item); >>   >> -#if defined(__mips__) || defined(__powerpc__) >> +#ifndef __LP64__ >>  #define UNR64_LOCKED >>  #endif >>   >> > > This seems like a wholly unsatisfying solution compared to how trivial > it would be to do something like have each arch's atomic.h set a symbol > to indicate whether 64-bit atomics are available. Dismissing 32-bit > arches because you don't perceive performance to be important there > doesn't seem like a valid argument. I think you are free to adjust the #ifdef if you find that it actually makes a difference. unr lists have been using a mutex on 32-bit architectures the entire time the API has existed, and I'm not sure you are running -j128 poudriere package builds on a raspberry pi to get the kind of workload where this lock contention matters. -- John Baldwin