From mboxrd@z Thu Jan 1 00:00:00 1970 From: Edward Shishkin Subject: Re: Question about memory pressure freezes Date: Sun, 29 Jul 2007 01:36:49 +0400 Message-ID: <46ABB6F1.6060304@namesys.com> References: <1185488757.33588.6.camel@localhost> <6ec7a4340707261840r34a68951s26a2691778c3ca15@mail.gmail.com> <1185557881.8434.6.camel@localhost> <6ec7a4340707271852y870e692sd7dddbe2916e4779@mail.gmail.com> Mime-Version: 1.0 Content-Transfer-Encoding: 7bit Return-path: In-Reply-To: <6ec7a4340707271852y870e692sd7dddbe2916e4779@mail.gmail.com> Sender: reiserfs-devel-owner@vger.kernel.org List-Id: Content-Type: text/plain; charset="us-ascii"; format="flowed" To: Xu CanHao Cc: Zan Lynx , reiserfs-devel@vger.kernel.org Xu CanHao wrote: >Hello! > > Since the default atom_max_size is RAM/4, that means 256MB of >maximum atom in your computer, and your HDD does 30MB/s which means >you'll have 8s-9s "flush/system freeze" time. > > IIRC, edward said the atom_max_size mount option is useless, > It is useless for remount, in other cases it works fine (for root file system it makes sense to edit fstab). So you can pass the option "tmgr.atom_max_size=N", where N is atom size in blocks > so >I'd suggest you modify your reiser4/init_super.c and change: > sbinfo->tmgr.atom_max_size = totalram_pages / 4; >to > sbinfo->tmgr.atom_max_size = totalram_pages / 16; >which means your atom would have a maximum size of 64MB and a maximum >freeze time of only 2 seconds. > > Such nice linear dependency disappears with some workload, so freeze time is not comforting also for small atoms.. >Thanks! > > >2007/7/28, Zan Lynx : > > >>Edward answered my question mostly. >> >>But, I have 1 GB RAM and a Hitachi 7,200 RPM laptop drive. It does >>about 30 MB/s. >> >>On Fri, 2007-07-27 at 09:40 +0800, Xu CanHao wrote: >> >> >>>Hello! >>> >>> How much is your RAM? >>> What is the result of your HDD's hdparm -t? >>> >>>Thanks! >>> >>>2007/7/27, Zan Lynx : >>> >>> >>>>I have often experienced nearly full system freezes for up to five >>>>seconds at a time while memory is being flushed to disk. >>>> >>>>I'm not sure if this is a general Linux problem or a Reiser4 problem, so >>>>I thought I'd ask. >>>> >>>>A sysrq-T during the freeze shows many processes trying to acquire a >>>>memory page, and Reiser4 flushing atoms and doing sync things. >>>> >>>>My working theory right now is that Reiser4 spends time flushing a lot >>>>of data at once before returning. >>>> >>>>If I am right about that, would it not make more sense to flush a few >>>>pages, return to the kernel, flush a few more pages, return to the >>>>kernel, etc, etc? That way programs could get a bit of RAM and make >>>>some progress. >>>> >>>>Of course I could be completely off about what's going on. >>>>-- >>>>Zan Lynx >>>> >>>> >>>> >>>> >>-- >>Zan Lynx >> >> >> >> >- >To unsubscribe from this list: send the line "unsubscribe reiserfs-devel" in >the body of a message to majordomo@vger.kernel.org >More majordomo info at http://vger.kernel.org/majordomo-info.html > > > >