Date: Tue, 01 Feb 2011 10:49:23 +0100 From: Attila Nagy <bra@fsn.hu> To: Kostik Belousov <kostikbel@gmail.com> Cc: freebsd-fs@freebsd.org, freebsd-stable@freebsd.org, Ivan Voras <ivoras@freebsd.org> Subject: Re: tmpfs is zero bytes (no free space), maybe a zfs bug? Message-ID: <4D47D723.6000106@fsn.hu> In-Reply-To: <20110130110918.GR2518@deviant.kiev.zoral.com.ua> References: <4D36A2CF.1080508@fsn.hu> <20110119084648.GA28278@icarus.home.lan> <4D36B85B.8070201@fsn.hu> <ih6f1d$u16$1@dough.gmane.org> <20110119150200.GY2518@deviant.kiev.zoral.com.ua> <AANLkTinPZ8jP5yX2se5LLaBYP1dpbEAhX-u7Wr0NAGz4@mail.gmail.com> <20110130110918.GR2518@deviant.kiev.zoral.com.ua>
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On 01/30/11 12:09, Kostik Belousov wrote: > On Wed, Jan 19, 2011 at 05:27:38PM +0100, Ivan Voras wrote: >> On 19 January 2011 16:02, Kostik Belousov<kostikbel@gmail.com> wrote: >> >>>> http://people.freebsd.org/~ivoras/diffs/tmpfs.h.patch >>>> >>>> I don't think this is a complete solution but it's a start. If you can, >>>> try it and see if it helps. >>> This is not a start, and actually a step in the wrong direction. >>> Tmpfs is wrong now, but the patch would make the wrongness even bigger. >>> >>> Issue is that the current tmpfs calculation should not depend on the >>> length of the inactive queue or the amount of free pages. This data only >>> measures the pressure on the pagedaemon, and has absolutely no relation >>> to the amount of data that can be put into anonymous objects before the >>> system comes out of swap. >>> >>> vm_lowmem handler is invoked in two situations: >>> - when KVA cannot satisfy the request for the space allocation; >>> - when pagedaemon have to start the scan. >>> None of the situations has any direct correlation with the fact that >>> tmpfs needs to check, that is "Is there enough swap to keep all my >>> future anonymous memory requests ?". >>> >>> Might be, swap reservation numbers can be useful to the tmpfs reporting. >>> Also might be, tmpfs should reserve the swap explicitely on start, instead >>> of making attempts to guess how much can be allocated at random moment. >> Thank you for your explanation! I'm still not very familiar with VM >> and VFS. Could you also read my report at >> http://www.mail-archive.com/freebsd-current@freebsd.org/msg126491.html >> ? I'm curious about the fact that there is lots of 'free' memory here >> in the same situation. > This is another ugliness in the dynamic calculation. Your wired is around > 15GB, that is always greater then available swap + free + inactive. > As result, tmpfs_mem_info() always returns 0. > In this situation TMPFS_PAGES_MAX() seems to return negative value, and > then TMPFS_PAGES_AVAIL() clamps at 0. > Well, if nobody can take care of this now, could you please state this in the BUGS section of the tmpfs man page? Thanks,home | help
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