Message-ID: <435394A1.7000109@cosmosbay.com>
Date: Mon, 17 Oct 2005 14:10:09 +0200
From: Eric Dumazet <dada1@cosmosbay.com>
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To: dipankar@in.ibm.com
CC: Jean Delvare <khali@linux-fr.org>, torvalds@osdl.org,
       Serge Belyshev <belyshev@depni.sinp.msu.ru>,
       LKML <linux-kernel@vger.kernel.org>, Andrew Morton <akpm@osdl.org>,
       Manfred Spraul <manfred@colorfullife.com>
Subject: [RCU problem] was VFS: file-max limit 50044 reached
References: <Pine.LNX.4.64.0510161912050.23590@g5.osdl.org> <JTFDVq8K.1129537967.5390760.khali@localhost> <20051017084609.GA6257@in.ibm.com> <43536A6C.102@cosmosbay.com> <20051017103244.GB6257@in.ibm.com>
In-Reply-To: <20051017103244.GB6257@in.ibm.com>
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Dipankar Sarma a ?crit :
> On Mon, Oct 17, 2005 at 11:10:04AM +0200, Eric Dumazet wrote:
>>
>>Fixing the 'file count' wont fix the real problem : Batch freeing is good 
>>but should be limited so that not more than *billions* of file struct are 
>>queued for deletion.
> 
> 
> Agreed. It is not designed to work that way, so there must be
> a bug somewhere and I am trying to track it down. It could very well
> be that at maxbatch=10 we are just queueing at a rate far too high
> compared to processing.
> 

I can freeze my test machine with a program that 'only' use dentries, no files.

No message, no panic, but machine becomes totally unresponsive after few seconds.

Just greping for call_rcu in kernel sources gave me another call_rcu() use 
from syscalls. And yes 2.6.13 has the same problem.

Here is the killer on by HT Xeon machine (2GB ram)

Eric


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#include <unistd.h>
#include <sys/types.h>
#include <fcntl.h>
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/stat.h>

int main(void)
{
	int i, rc;	
	struct stat st;
	char name[1024];

	memset(name, 'a', sizeof(name));

	for (i = 0; i < 1000000000;i++) {
		sprintf(name + 220, "%d", i);
		rc = stat(name, &st);
		if (rc == -1 && errno != ENOENT) {
			perror(name);
		}
	}
	return 0;
}

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