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Date:      Thu, 23 Jan 2020 14:00:50 +0100
From:      Miroslav Lachman <000.fbsd@quip.cz>
To:        Wojciech Puchar <wojtek@puchar.net>
Cc:        freebsd-hackers@freebsd.org
Subject:   Re: slow directory operation on huge dirs
Message-ID:  <cf4d3d5f-6c9e-81cf-f6a2-ade177b9f8ff@quip.cz>
In-Reply-To: <alpine.BSF.2.20.2001231245190.98419@puchar.net>
References:  <alpine.BSF.2.20.2001191930040.17538@puchar.net> <alpine.BSF.2.20.2001231245190.98419@puchar.net>

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Wojciech Puchar wrote on 2020/01/23 12:45:
> 
> 
> On Sun, 19 Jan 2020, Wojciech Puchar wrote:
> 
>> i have UFS_DIRHASH enabled and enough large dirhash_maxmem
>> yet when there is heavy I/O on large directory (like dovecot indexing 
>> so it reads every file) it randomly works fast or slow. Most often slow.
>> Whole system slows down, and system cpu usage gets above 50% on quad 
>> core Xeon.
>>
>> lowering maxvnodes from 500000 to 100000 "fixes" the problem.
>>
>> what is going on here?
>>
>> 11.3-STABLE from maybe 2 weeks ago.
>>
> nobody have idea what's the problem?

Is it "just slow" or is your disk too busy? (iostat)

Can it be that pre-cacheing on huge directory makes disk too busy 
because there is too much to read?

Miroslav Lachman



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