From owner-freebsd-current  Sun Nov  8 11:25:49 1998
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To: Dmitrij Tejblum <dima@tejblum.dnttm.rssi.ru>
cc: Eivind Eklund <eivind@yes.no>, John Fieber <jfieber@indiana.edu>,
        current@FreeBSD.ORG
Subject: Re: The infamous dying daemons bug 
In-reply-to: Your message of "Sun, 08 Nov 1998 21:06:29 +0300."
             <199811081806.VAA00888@tejblum.dnttm.rssi.ru> 
From: David Greenman <dg@root.com>
Reply-To: dg@root.com
Date: Sun, 08 Nov 1998 11:24:08 -0800
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X-Loop: FreeBSD.ORG

>Eivind Eklund wrote:
>> 
>> Oh, and another aspect: This suddenly started happening.  It has been
>> stable for 3/4 of a year, and then suddenly started happening
>> reproducably one day, after a kernel update while John was doing his
>> changes.
>
>Please don't tell anyone, but I am almost convinced that the bug is 
>here:
>
>-----swap_pager.c, line 1132------
>                /*
>                 * If we're out of swap space, then attempt to free
>                 * some whenever multiple pages are brought in. We
>                 * must set the dirty bits so that the page contents
>                 * will be preserved.
>                 */
>                if (SWAPLOW ||
>                        (vm_swap_size < btodb((cnt.v_page_count - cnt.v_wire_count)) * PAGE_SIZE)) {
>                        for (i = 0; i < count; i++) {
>                                m[i]->dirty = VM_PAGE_BITS_ALL;
>                        }
>                        swap_pager_freespace(object,
>                                m[0]->pindex + paging_offset, count);   
>                }
>------------------------------------
>If I sysctl out the call to swap_pager_freespace, all symptoms 
>disappear. This code activates at about the time when the "suggest more 
>swap space" message printed. IIRC, it was introduced by John Dyson this 
>winter.
>
>(Perhaps, the code just triggers a bug elsewhere... No idea what is 
>wrong).

   I don't see anything wrong with it, but if it is the cause of the
problem, it can safely be removed. I'd suggest that people #if 0 out
the code and see if the problem completely vanishes.

-DG

David Greenman
Co-founder/Principal Architect, The FreeBSD Project

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