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From: "Rodney W. Grimes" <freebsd@pdx.rh.CN85.dnsmgr.net>
Message-Id: <201804271429.w3RETMCl006821@pdx.rh.CN85.dnsmgr.net>
Subject: Re: svn commit: r333052 - head/sys/vm
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To: Mateusz Guzik <mjg@freebsd.org>
Date: Fri, 27 Apr 2018 07:29:22 -0700 (PDT)
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[ Charset UTF-8 unsupported, converting... ]
> Author: mjg
> Date: Fri Apr 27 05:37:35 2018
> New Revision: 333052
> URL: https://svnweb.freebsd.org/changeset/base/333052
> 
> Log:
>   uma: whack main zone counter update in the slow path

Remove might be a better word, whack is ambigous in this context.

>   Cached counters are typically zero at this point so it performs
>   avoidable atomics. Everything reading them also reads the cached
>   ones, thus there is really no point.

No point in?  reading them, writting them, updating them?

>   
>   Reviewed by:		jeff
> 
> Modified:
>   head/sys/vm/uma_core.c
> 
> Modified: head/sys/vm/uma_core.c
> ==============================================================================
> --- head/sys/vm/uma_core.c	Fri Apr 27 05:36:02 2018	(r333051)
> +++ head/sys/vm/uma_core.c	Fri Apr 27 05:37:35 2018	(r333052)
> @@ -2329,14 +2329,6 @@ zalloc_start:
>  	cpu = curcpu;
>  	cache = &zone->uz_cpu[cpu];
>  
> -	/*
> -	 * Since we have locked the zone we may as well send back our stats.
> -	 */
> -	atomic_add_long(&zone->uz_allocs, cache->uc_allocs);
> -	atomic_add_long(&zone->uz_frees, cache->uc_frees);
> -	cache->uc_allocs = 0;
> -	cache->uc_frees = 0;
> -
>  	/* See if we lost the race to fill the cache. */
>  	if (cache->uc_allocbucket != NULL) {
>  		ZONE_UNLOCK(zone);
> 
> 

-- 
Rod Grimes                                                 rgrimes@freebsd.org