Path: csiph.com!xmission!news.snarked.org!news.linkpendium.com!news.linkpendium.com!panix!usenet.stanford.edu!not-for-mail From: Chet Ramey Newsgroups: gnu.bash.bug Subject: Re: Unexpected delay in using arguments. Date: Tue, 14 Aug 2018 11:25:04 -0400 Lines: 47 Approved: bug-bash@gnu.org Message-ID: References: Reply-To: chet.ramey@case.edu NNTP-Posting-Host: lists.gnu.org Mime-Version: 1.0 Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 8bit X-Trace: usenet.stanford.edu 1534260313 523 208.118.235.17 (14 Aug 2018 15:25:13 GMT) X-Complaints-To: action@cs.stanford.edu Cc: chet.ramey@case.edu To: Bize Ma , bug-bash Envelope-to: bug-bash@gnu.org Openpgp: preference=signencrypt Autocrypt: addr=chet.ramey@case.edu; prefer-encrypt=mutual; keydata= xsDiBEEOsGwRBACFa0A1oa71HSZLWxAx0svXzhOZNQZOzqHmSuGOG92jIpQpr8DpvgRh40Yp AwdcXb8QG1J5yGAKeevNE1zCFaA725vGSdHUyypHouV0xoWwukYO6qlyyX+2BZU+okBUqoWQ koWxiYaCSfzB2Ln7pmdys1fJhcgBKf3VjWCjd2XJTwCgoFJOwyBFJdugjfwjSoRSwDOIMf0D /iQKqlWhIO1LGpMrGX0il0/x4zj0NAcSwAk7LaPZbN4UPjn5pqGEHBlf1+xDDQCkAoZ/VqES GZragl4VqJfxBr29Ag0UDvNbUbXoxQsARdero1M8GiAIRc50hj7HXFoERwenbNDJL86GPLAQ OTGOCa4W2o29nFfFjQrsrrYHzVtyA/9oyKvTeEMJ7NA3VJdWcmn7gOu0FxEmSNhSoV1T4vP2 1Wf7f5niCCRKQLNyUy0wEApQi4tSysdz+AbgAc0b/bHYVzIf2uO2lIEZQNNt+3g2bmXgloWm W5fsm/di50Gm1l1Na63d3RZ00SeFQos6WEwLUHEB0yp6KXluXLLIZitEJM0gQ2hldCBSYW1l eSA8Y2hldC5yYW1leUBjYXNlLmVkdT7CYQQTEQIAIQIbAwYLCQgHAwIDFQIDAxYCAQIeAQIX gAUCRX3FIgIZAQAKCRC7WGnwZOp0q069AKCNDRn+zzN/AHbaynls/Lvq1kH/RQCgkLvF8bDs maUHSxSIPqzlGuKWDxbOwE0EQQ6wbxAEAJCukwDigRDPhAuI+lf+6P64lWanIFOXIndqhvU1 3cDbQ/Wt5LwPzm2QTvd7F+fcHOgZ8KOFScbDpjJaRqwIybMTcIN0B2pBLX/C10W1aY+cUrXZ gXUGVISEMmpaP9v02auToo7XXVEHC+XLO9IU7/xaU98FL69l6/K4xeNSBRM/AAMHA/wNAmRB pcyK0+VggZ5esQaIP/LyolAm2qwcmrd3dZi+g24s7yjV0EUwvRP7xHRDQFgkAo6++QbuecU/ J90lxrVnQwucZmfz9zgWDkT/MpfB/CNRSKLFjhYq2yHmHWT6vEjw9Ry/hF6Pc0oh1a62USdf aKAiim0nVxxQmPmiRvtCmcJJBBgRAgAJBQJBDrBvAhsMAAoJELtYafBk6nSr43AAn2ZZFQg8 Gs/zUzvXMt7evaFqVTzcAJ0cHtKpP1i/4H4R9+OsYeQdxxWxTQ== User-Agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.13; rv:52.0) Gecko/20100101 Thunderbird/52.9.1 In-Reply-To: Content-Language: en-US X-Junkmail-Status: score=7/90, host=mpv1-2015.case.edu X-Junkmail-PrAS-Raw: score=7/90, refid=2.7.2:2018.8.14.140316:17:7.944, ip=, rules=__HAS_REPLYTO, __HAS_CC_HDR, __SUBJ_REPLY, __BOUNCE_CHALLENGE_SUBJ, __BOUNCE_NDR_SUBJ_EXEMPT, __TO_MALFORMED_2, __TO_NAME, __TO_NAME_DIFF_FROM_ACC, __REFERENCES, __HAS_FROM, FROM_EDU_TLD, __HAS_MSGID, __SANE_MSGID, DATE_TZ_NA, __USER_AGENT, __MOZILLA_USER_AGENT, __MIME_VERSION, __IN_REP_TO, __CT, __CT_TEXT_PLAIN, __CTE, __REPLYTO_SAMEAS_FROM_ADDY, __REPLYTO_SAMEAS_FROM_ACC, __FROM_DOMAIN_IN_ANY_CC1, __FROM_DOMAIN_IN_ANY_CC2, __REPLYTO_SAMEAS_FROM_DOMAIN, __ANY_URI, __URI_WITH_PATH, __URI_NO_WWW, __HIGHBITS, __CP_URI_IN_BODY, __FRAUD_MONEY_CURRENCY_DOLLAR, __SUBJ_ALPHA_NEGATE, __URI_IN_BODY, __URI_NOT_IMG, __FORWARDED_MSG, __NO_HTML_TAG_RAW, BODYTEXTP_SIZE_3000_LESS, BODY_SIZE_1400_1499, __MIME_TEXT_P1, __MIME_TEXT_ONLY, __URI_NS, HTML_00_01, HTML_00_10, __FRAUD_MONEY_CURRENCY, BODY_SIZE_5000_LESS, IN_REP_TO, MSG_THREAD, __FROM_DOMAIN_IN_RCPT, [TRUNCATED], so=2010-03-03 19:42:08, dmn=2016-08-03-0138 X-detected-operating-system: by eggs.gnu.org: GNU/Linux 2.4.x-2.6.x [generic] X-Received-From: 129.22.103.226 X-BeenThere: bug-bash@gnu.org X-Mailman-Version: 2.1.21 Precedence: list List-Id: Bug reports for the GNU Bourne Again SHell List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Xref: csiph.com gnu.bash.bug:14485 On 8/12/18 3:16 AM, Bize Ma wrote: > Try this script: > >     #!/bin/bash >     TIMEFORMAT='%R' > >     n=1000 >     m=20000 > >     f1   () { :; } > >     f2   () { i=0;  time while [ "$((i+=1))" -lt "$n" ]; do     :    ; done >           i=0;  time while [ "$((i+=1))" -lt "$n" ]; do     f1    ; done >         } > >     test1() { set -- $(seq $m) >           f2  "" >           f2 "$@" >         } >     test1 > > To get: > >       0.019 >       0.028 >       0.019 >     19.204 > > Which is a thousand times slower. If you build a profiling version of bash, you'll find that about 75% of that time is spent copying the list of arguments around, since you have to save and restore it each time you call f1. Looking at making that more efficient has been a low-level task for a while now. > Bash 5 is even worse, try: Bash-5.0-alpha is not a released version, so it uses the debugging malloc. If you profile that, you'll find that about 99% of the time is spent marking allocations as active and free in the table the bash malloc uses to keep track of active memory. -- ``The lyf so short, the craft so long to lerne.'' - Chaucer ``Ars longa, vita brevis'' - Hippocrates Chet Ramey, UTech, CWRU chet@case.edu http://tiswww.cwru.edu/~chet/