From mboxrd@z Thu Jan 1 00:00:00 1970 From: Andreas Rohner Subject: Re: [PATCH 2/6] nilfs2: add new timestamp to seg usage and function to change su_nblocks Date: Sun, 16 Mar 2014 17:02:42 +0100 Message-ID: <5325CB22.5010904@gmx.net> References: <12561ce5e2cf8ae07fdda05e16c357f37d17c62f.1394966729.git.andreas.rohner@gmx.net> <2FD47FE0-3468-4EF4-AAAE-4A636C640C44@dubeyko.com> <53259801.5080409@gmx.net> <0ED0D5DA-9AE9-44B8-8936-1680DE2B64C5@dubeyko.com> Mime-Version: 1.0 Content-Transfer-Encoding: QUOTED-PRINTABLE Return-path: In-Reply-To: <0ED0D5DA-9AE9-44B8-8936-1680DE2B64C5-yeENwD64cLxBDgjK7y7TUQ@public.gmane.org> Sender: linux-nilfs-owner-u79uwXL29TY76Z2rM5mHXA@public.gmane.org List-ID: Content-Type: text/plain; charset="utf-8" To: Vyacheslav Dubeyko Cc: "linux-nilfs-u79uwXL29TY76Z2rM5mHXA@public.gmane.org" On 2014-03-16 14:34, Vyacheslav Dubeyko wrote: >=20 >> On 16 =D0=BC=D0=B0=D1=80=D1=82=D0=B0 2014 =D0=B3., at 16:24, Andreas= Rohner wrote: >> >>> On 2014-03-16 14:00, Vyacheslav Dubeyko wrote: >>> >>>> On Mar 16, 2014, at 1:47 PM, Andreas Rohner wrote: >>>> >>>> This patch adds an additional timestamp to the segment usage >>>> information that indicates the last time the usage information was >>>> changed. So su_lastmod indicates the last time the segment itself = was >>>> modified and su_lastdec indicates the last time the usage informat= ion >>>> itself was changed. >>> >>> What will we have if user changes time? >>> What sequence will we have after such "malicious" action? >>> Did you test such situation? >> >> The timestamp is just a hint for the userspace GC. If the hint is wr= ong >> the result would be that the GC is less efficient for a while. After= a >> while it would go back to normal. You have the same problem with the >> already existing su_lastmod timestamp. >> >=20 > But I worry about such thing. Previously, we had complains of users a= bout > different issues with timestamp policy of GC. And I had hope that nam= ely > new GC policies can resolve such GC disadvantage. So, what have we ag= ain? > The same issue of GC? Yes but I have to compare it to the protection period, which is a timestamp. Maybe I could use the current checkpoint number instead... Regards, Andreas Rohner > Thanks, > Vyacheslav Dubeyko. >=20 > -- > To unsubscribe from this list: send the line "unsubscribe linux-nilfs= " in > the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org > More majordomo info at http://vger.kernel.org/majordomo-info.html >=20 -- To unsubscribe from this list: send the line "unsubscribe linux-nilfs" = in the body of a message to majordomo-u79uwXL29TY76Z2rM5mHXA@public.gmane.org More majordomo info at http://vger.kernel.org/majordomo-info.html