Date: Fri, 7 Jan 2011 08:20:11 +0100 From: Andre Albsmeier <Andre.Albsmeier@siemens.com> To: Alexander Leidinger <Alexander@leidinger.net> Cc: "freebsd-emulation@freebsd.org" <freebsd-emulation@freebsd.org> Subject: Re: 7.3-STABLE and Linux version of SIMetrix Message-ID: <20110107072011.GA3905@curry.mchp.siemens.de> In-Reply-To: <20110106132857.11513i1k24thhwug@webmail.leidinger.net> References: <20101230075124.GA12923@curry.mchp.siemens.de> <20101231144800.00005c6d@unknown> <20110101224629.GA30540@curry.mchp.siemens.de> <20110102115021.00000c8b@unknown> <20110105191915.GA43997@curry.mchp.siemens.de> <20110106090130.20784sf1w9verdic@webmail.leidinger.net> <20110106104057.GB59969@curry.mchp.siemens.de> <20110106132857.11513i1k24thhwug@webmail.leidinger.net>
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On Thu, 06-Jan-2011 at 13:28:57 +0100, Alexander Leidinger wrote: > Quoting Andre Albsmeier <Andre.Albsmeier@siemens.com> (from Thu, 6 Jan > 2011 11:40:57 +0100): > > > On Thu, 06-Jan-2011 at 09:01:30 +0100, Alexander Leidinger wrote: > >> Quoting Andre Albsmeier <Andre.Albsmeier@siemens.com> (from Wed, 5 Jan > >> 2011 20:19:15 +0100): > >> > >> > Got it running... A short explanation: > >> > > >> > Linux' shm_open() fails because it wants to find some funky shmfs > >> > to construct the full pathname. It starts to search at the default > >> > mountpoint which is /dev/shm. If this fails it runs through fstab > >> > and searches for shmfs and tmpfs. Whatever it finds will be > >> > statfs()'ed to be checked for Linux' fs magic for shmfs (0x01021994). > >> > >> What does it expect as a filesystem type if it does not find shmfs in > >> fstab but tmpfs? If it does not find tmpfs, will it try /tmp anyway > >> (but check for some fstype magic)? > > > > It searches for every mount which is of type tmpfs or shm. > > Whatever it finds must have the fs magic SHMFS_SUPER_MAGIC > > (0x01021994). It's in sysdeps/unix/sysv/linux/shm_open.c: > > > > ------------------------- snip ------------------- > > > > /* Now read the entries. */ > > while ((mp = __getmntent_r (fp, &resmem, buf, sizeof buf)) != NULL) > > /* The original name is "shm" but this got changed in early Linux > > 2.4.x to "tmpfs". */ > > This looks like it is creating real files there, and the tmpfs thing Yes, that's true. > shall make sure it is empty after a reboot. That's just an assumption... Possibly. I have also seen statements in mailing lists where they talk about that fs being some kind of memory based fs to increase speed. > > Do you have some temporary files in the location your /dev/shm points > to during running the linux application which needs it (I do not > expect that our implementation creates them, but as I haven't looked > at the code yet, this is something to be verified)? Yes. In the case of my application (SIMetrix) files with a size of approx. 1,3 MB are created and then removed. -Andre > > Bye, > Alexander. > > -- > Is death legally binding? > > http://www.Leidinger.net Alexander @ Leidinger.net: PGP ID = B0063FE7 > http://www.FreeBSD.org netchild @ FreeBSD.org : PGP ID = 72077137 > -- Micro$oft: Which virus will you get today?
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