[Gluster-devel] how do you debug ref leaks?
dlambrig at redhat.com
Thu Sep 18 15:40:37 UTC 2014
If we could disable/enable ref tracking dynamically, it may only be "heavy weight" tempoarily while the customer is being observed.
You could get a state dump , or another idea is to take a core of the live process. gcore $(pidof processname)
----- Original Message -----
> From: "Pranith Kumar Karampuri" <pkarampu at redhat.com>
> To: "Shyam" <srangana at redhat.com>, gluster-devel at gluster.org
> Sent: Thursday, September 18, 2014 11:34:28 AM
> Subject: Re: [Gluster-devel] how do you debug ref leaks?
> On 09/18/2014 07:48 PM, Shyam wrote:
> > On 09/17/2014 10:13 PM, Pranith Kumar Karampuri wrote:
> >> hi,
> >> Till now the only method I used to find ref leaks effectively is to
> >> find what operation is causing ref leaks and read the code to find if
> >> there is a ref-leak somewhere. Valgrind doesn't solve this problem
> >> because it is reachable memory from inode-table etc. I am just wondering
> >> if there is an effective way anyone else knows of. Do you guys think we
> >> need a better mechanism of finding refleaks? At least which decreases
> >> the search space significantly i.e. xlator y, fop f etc? It would be
> >> better if we can come up with ways to integrate statedump and this infra
> >> just like we did for mem-accounting.
> >> One way I thought was to introduce new apis called
> >> xl_fop_dict/inode/fd_ref/unref (). Each xl keeps an array of num_fops
> >> per inode/dict/fd and increments/decrements accordingly. Dump this info
> >> on statedump.
> >> I myself am not completely sure about this idea. It requires all xlators
> >> to change.
> >> Any ideas?
> > On a debug build we can use backtrace information stashed per ref and
> > unref, this will give us history of refs taken and released. Which
> > will also give the code path where ref was taken and released.
> > It is heavy weight, so not for non-debug setups, but if a problem is
> > reproducible this could be a quick way to check who is not releasing
> > the ref's or have a history of the refs and unrefs to dig better into
> > code.
> Do you have any ideas for final builds also? Basically when users report
> leaks it should not take us too long to figure out the problem area. We
> should just ask them for statedump and should be able to figure out the
> > Shyam
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