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From: Alfred Perlstein <bright@mu.org>
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To: Konstantin Belousov <kib@FreeBSD.org>
Subject: Re: svn commit: r251282 - head/sys/kern
References: <201306030416.r534GmCA001872@svn.freebsd.org>
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Hey Konstaintin, shouldn't this be scaled against the actual amount of 
KVA we have instead of an arbitrary limit?

-Alfred

On 6/2/13 9:16 PM, Konstantin Belousov wrote:
> Author: kib
> Date: Mon Jun  3 04:16:48 2013
> New Revision: 251282
> URL: http://svnweb.freebsd.org/changeset/base/251282
>
> Log:
>    When auto-sizing the buffer cache, limit the amount of physical memory
>    used as the estimation of size, to 32GB.  This provides around 100K of
>    buffer headers and corresponding KVA for buffer map at the peak.
>    Sizing the cache larger is not useful, also resulting in the wasting
>    and exhausting of KVA for large machines.
>    
>    Reported and tested by:	bdrewery
>    Sponsored by:	The FreeBSD Foundation
>
> Modified:
>    head/sys/kern/vfs_bio.c
>
> Modified: head/sys/kern/vfs_bio.c
> ==============================================================================
> --- head/sys/kern/vfs_bio.c	Mon Jun  3 04:11:42 2013	(r251281)
> +++ head/sys/kern/vfs_bio.c	Mon Jun  3 04:16:48 2013	(r251282)
> @@ -560,7 +560,8 @@ kern_vfs_bio_buffer_alloc(caddr_t v, lon
>   			nbuf += min((physmem_est - 4096) / factor,
>   			    65536 / factor);
>   		if (physmem_est > 65536)
> -			nbuf += (physmem_est - 65536) * 2 / (factor * 5);
> +			nbuf += min((physmem_est - 65536) * 2 / (factor * 5),
> +			    32 * 1024 * 1024 / (factor * 5));
>   
>   		if (maxbcache && nbuf > maxbcache / BKVASIZE)
>   			nbuf = maxbcache / BKVASIZE;
>