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Keith, I know what you are asking for and need. It is a requirement to be "Enterprise". What you are seeking will take time, and effort. I have explained successfully to Jens (block maintainer) the issues of data integrity. If you can prove this becomes a data integrity issue, which I know it is for the general case, your argument will have strength. Nothing stops "fastfreenet.com" from funding the development time. ASS-GAS-GRASS-CASH, Linux is free but my time is not. If you want to discuss more of this offline, I will listen and help make the case. Cheers, Andre Hedrick LAD Storage Consulting Group On Thu, 10 Apr 2003, Keith Ansell wrote: > Thank you for your prompt replies. > > I realise that Linux conforms to the letter of the specification, but maybe > not the spirit of the it. > > I am porting a Database solution to Linux from Unix SVR4, Sco OpenServer and > AIX, where all write required memory mapped files are flushed to disk with > the system flusher, my users have large systems (some in excess of 600 > concurrent connections) flushing memory mapped files is a big part of are > systems performance. This ensures that in the event of a catastrophic > system failure the customers vitual business data has been written to disk . > > Keith Ansell > > > > > > > ----- Original Message ----- > From: "Andrew Morton" <akpm@digeo.com> > To: "Andre Hedrick" <andre@linux-ide.org> > Cc: <keitha@edp.fastfreenet.com>; <linux-kernel@vger.kernel.org>; > <axboe@suse.de> > Sent: Wednesday, April 09, 2003 10:27 AM > Subject: Re: bdflush flushing memory mapped pages. > > > > Andre Hedrick <andre@linux-ide.org> wrote: > > > > > > > > > Funny you mention this point! > > > > > > I just spent 30-45 minutes on the phone talking to Jens about this very > > > issue. Jens states he can map the model in to 2.5. and will give it a > > > fling in a bit. This issue is a must; however, I had given up on the > idea > > > until 2.7. However, the issues he and I addressed, in combination to > your > > > request jive in sync. > > > > noooo..... This isn't going to happen. There are many reasons. > > > > Firstly, how can bdflush even know what pages to write? The dirtiness of > > these pages is recorded *only* in some processor's hardware pte cache > and/or > > the software pagetables. Someone needs to go tell all the CPUs to > writeback > > their pte caches into the pagetables and then someone needs to walk the > > pagetables propagating the pte dirty bit into the pageframes before we can > > even start the I/O. > > > > That's what msync does, in filemap_sync(). > > > > > > And even if bdflush did this automagically, it's the wrong thing to do > > because the application could very well be repeatedly dirtying the pages. > > Very probably. So we've just gone and done a ton of pointless I/O, over > and > > over. > > > > You can view MAP_SHARED as an IPC mechanism which uses the filesystem > > namespace for naming. No way do these people want bdflush pointlessly > > hammering the disk. > > > > You can also view MAP_SHARED as a (strange) way of writing files out. If > you > > want to do that then fine, but you need to tell the kernel when you've > > finished, just like write() does. You do that with msync. > > > > > > > > - > > To unsubscribe from this list: send the line "unsubscribe linux-kernel" in > > the body of a message to majordomo@vger.kernel.org > > More majordomo info at http://vger.kernel.org/majordomo-info.html > > Please read the FAQ at http://www.tux.org/lkml/ > > > - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/ | ||||||||||||
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