From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from eggs.gnu.org ([2001:4830:134:3::10]:42230) by lists.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YvFx3-0004h0-68 for qemu-devel@nongnu.org; Wed, 20 May 2015 22:11:14 -0400 Received: from Debian-exim by eggs.gnu.org with spam-scanned (Exim 4.71) (envelope-from ) id 1YvFwy-0006Zp-SI for qemu-devel@nongnu.org; Wed, 20 May 2015 22:11:13 -0400 Received: from szxga02-in.huawei.com ([119.145.14.65]:50706) by eggs.gnu.org with esmtp (Exim 4.71) (envelope-from ) id 1YvFwy-0006ZO-Ao for qemu-devel@nongnu.org; Wed, 20 May 2015 22:11:08 -0400 Message-ID: <555D3E97.4000806@huawei.com> Date: Thu, 21 May 2015 10:10:31 +0800 From: Gonglei MIME-Version: 1.0 References: <33183CC9F5247A488A2544077AF1902086E86BFF@SZXEMA503-MBS.china.huawei.com> <555C9DA1.7060204@redhat.com> In-Reply-To: <555C9DA1.7060204@redhat.com> Content-Type: text/plain; charset="utf-8" Content-Transfer-Encoding: 7bit Subject: Re: [Qemu-devel] [RFC] Can we convert UTC time to local time in Qemu List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , To: Eric Blake , "qemu-devel@nongnu.org" Cc: "Huangpeng (Peter)" , "Herongguang (Stephen)" On 2015/5/20 22:43, Eric Blake wrote: > On 05/20/2015 12:29 AM, Gonglei (Arei) wrote: >> Hi, >> >> At present, Qemu use g_time_val_to_iso8601() to get the UTC added to error_report() >> (commit 5e2ac5191), TBH this way is very simply, we just need invoke standard glib functions to >> complete the job. > > local time is ambiguous (daylight savings, and even consider what > happens when you physically relocate your machine to a different time > zone). UTC is better. > Actually this is a scenario that happen unlikely. :( >> >> But in the cloud computing and data center scenarios, there are many >> Other open source components, such as kernel, libvirt, openstack which are all using local time >> to record the message logs, only Qemu is using the UTC time. When we want to find a error >> message of Qemu, we should convert the UTC time to local time manually, and unfortunately >> different countries have different local time, what a trouble thing the converting is. >> >> So, my question is: Can we convert the UTC time to local time in Qemu? > > Actually, libvirt uses UTC on purpose, not only because it is > unambiguous, but because it prints timestamps even in situations where > it must be async-signal safe, and there is no async-signal-safe way to > determine the offset required to convert UTC to local time. > Yes, I got it. >> >> Any thoughts? Thanks. > > I'd rather stick with UTC in logs (but perhaps make it more obvious that > the timestamp is UTC by actually sticking that string as part of the > timestamp - libvirt is not currently doing that). > OK, I agree, will post a patch to Qemu maillist. Regards, -Gonglei