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Message-ID: <49C80685.9060800@redhat.com> Date: Mon, 23 Mar 2009 17:00:37 -0500 From: Eric Sandeen <sandeen@...hat.com> To: Don Porter <porterde@...utexas.edu> CC: linux-ext4@...r.kernel.org Subject: Re: ext3 leaking buffer_heads Don Porter wrote: > Hi, > > It appears that the ext3 journal code has a slow leak of buffer_head > structs. Try this simple script: > > perl -e 'while(1){ `sync`; }' > > and monitor the count of allocated buffer_head structs in > /proc/slabinfo, and it seems to increase without bound. Even after this > script is killed and the machine is left idle for several minutes, the > count of buffer heads doesn't substantially decrease. > > Looking around at various machines I have access to, the count of > allocated buffer_heads roughly correlates with uptime when using ext3. > This is a slow leak - one would likely have to run this script for a day > or more to drain enough lowmem to cause problems. > > Other info: I have only tried this on x86 machines, but I have tried > both 2.6.22.6 and 2.6.28.8, and both have the problem. I am running > Ubuntu 7.10 on top of these kernels, but the kernels were built directly > from kernel.org tarballs. > > Any advice or help with this issue is greatly appreciated. Without investigating too far yet, I did try this, and did indeed see the buffer_head usage go up while the script runs. However, if I did: # echo 3 > /proc/sys/vm/drop_caches before the script, and noted the total nr. of buffer heads in use, and then did it again after the script had been running a while, I got back to the same (low) count of buffer heads in use. So I don't think this is a leak as in "the system has lost all accounting of these buffer heads" at least... but it'd be interesting to know what the reason for the increase is, I'm not sure offhand. -Eric -- To unsubscribe from this list: send the line "unsubscribe linux-ext4" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html
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