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Sat, 10 Apr 2021 00:54:57 +0000 Received: by kubenode544.mail-prod1.omega.ir2.yahoo.com (VZM Hermes SMTP Server) with ESMTPA ID dc82fd2bb8881ba7b9b4066043bac33a; Sat, 10 Apr 2021 00:54:52 +0000 (UTC) Received: from [192.168.178.21] (helo=hydra) by mail.kiddle.eu with esmtp(Exim 4.93.0.4) (envelope-from ) id 1lV1tj-000NvL-8r for zsh-workers@zsh.org; Sat, 10 Apr 2021 02:54:51 +0200 In-reply-to: From: Oliver Kiddle References: To: zsh-workers@zsh.org Subject: Re: [PATCH] readhistfile: avoid thousands of lseek(2) syscalls via ftell() MIME-Version: 1.0 Content-Type: text/plain; charset="us-ascii" Content-ID: <91965.1618016091.1@hydra> Date: Sat, 10 Apr 2021 02:54:51 +0200 Message-ID: <91966-1618016091.272434@pUFi.MzyD.eXSj> X-Mailer: WebService/1.1.18121 mail.backend.jedi.jws.acl:role.jedi.acl.token.atz.jws.hermes.yahoo Apache-HttpAsyncClient/4.1.4 (Java/16) X-Seq: 48462 Archived-At: X-Loop: zsh-workers@zsh.org Errors-To: zsh-workers-owner@zsh.org Precedence: list Precedence: bulk Sender: zsh-workers-request@zsh.org X-no-archive: yes List-Id: List-Help: List-Subscribe: List-Unsubscribe: List-Post: List-Owner: List-Archive: On 7 Feb 2020, Michael Stapelberg wrote: > Before this change, zsh startup time was dominated by lseek(2) system calls on > the history file, as shown by strace -c: This patch never got applied. 45768 is almost identical. I tried timing the readhistline function with dtrace on FreeBSD to see if this is perhaps only relevant with glibc. It didn't appear to result in particularly great savings however when measuring a few times, I did consistently get better performance with the patch than without. That was with a fast local disk and of the order of microseconds - certainly not enough to be discernable. Over NFS, timings were erratic. Having read through both patches, nothing caught my attention as being a concern. 45396 keeps track of number of bytes read while 45768 does the same with file position in an off_t variable. The first doesn't duplicate a strlen() call which is preferable but the second patch could be tweaked to do likewise. Does anyone have a preference between them? If nobody else has any particular views on the patch(es), I'm inclined to apply, probably the first one. Oliver