Messages in this thread | | | Date | Tue, 7 Oct 2003 00:01:32 +0530 | From | Dipankar Sarma <> | Subject | Re: [RFC 0/6] Backing Store for sysfs |
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On Mon, Oct 06, 2003 at 11:09:07AM -0700, Greg KH wrote: > On Mon, Oct 06, 2003 at 11:31:19PM +0530, Dipankar Sarma wrote: > No. My main point is that for every hotplug event (which is caused by a > kobject being created or destroyed), udev will run and look at the sysfs > entry for the kobject (by using libsysfs which reads in all of the > kobject information, including attributes). This is a normal event, so > we have to care about what happens after running 'find' on the sysfs > tree as that is basically what will always happen. > > Does that make more sense? We can't just look at what happens with this > patch without actually accessing all of the sysfs tree, as that will be > the "normal" case.
That sounds odd. So, udev essentially results in a frequent and continuous "find /sys" ? That doesn't sound good. You are unnecessarily adding pressure on vfs (dcache specially). We will discuss this offline then and see what needs to be done.
> > > Can you show this happening? > > > > It should be easy to demonstrate. That is how dentries/inodes > > work for on-disk filesystems. If Maneesh's patch didn't work that > > way, then the whole point is lost. I hope that is not the case. > > Me too. It's just that the free memory numbers didn't show much gain > with this patch on his system. That worries me.
Well, Maneesh didn't post numbers after letting the system age out sysfs dentries/inodes. Maneesh can you post some such numbers ?
> > > But again, I don't think the added overhead you have added to a kobject > > > is acceptable for not much gain for the normal case (systems without a > > > zillion devices.) > > > > IIRC, Maneesh test machine is a 2-way P4 xeon with six scsi disks and savings > > are of about 800KB. That is as normal a case as it gets, I think. > > It only gets better as you have more devices in your system. > > 800Kb after running find? I don't see that :)
No, those numbers were for just mounting sysfs. More numbers tomorrow.
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