Date: Wed, 22 May 2019 19:19:45 +0300 From: Slawa Olhovchenkov <slw@zxy.spb.ru> To: Alexander Motin <mav@FreeBSD.org> Cc: lev@FreeBSD.org, Mark Johnston <markj@freebsd.org>, freebsd-fs@freebsd.org, freebsd-hackers@freebsd.org Subject: Re: Commit r345200 (new ARC reclamation threads) looks suspicious to me - second potential problem Message-ID: <20190522161945.GE47119@zxy.spb.ru> In-Reply-To: <2a50e192-e672-7c87-178b-afd509a765df@FreeBSD.org> References: <369cb1e9-f36a-a558-6941-23b9b811825a@FreeBSD.org> <20190520164202.GA2130@spy> <28c7430b-fb7c-6472-5c1b-fa3ff63a9e73@FreeBSD.org> <94d051a3-3427-7a5b-efe7-169cff2265d3@FreeBSD.org> <2a50e192-e672-7c87-178b-afd509a765df@FreeBSD.org>
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On Wed, May 22, 2019 at 12:07:29PM -0400, Alexander Motin wrote: > On 22.05.2019 11:50, Lev Serebryakov wrote: > > On 22.05.2019 18:19, Alexander Motin wrote: > > > >>>> But looks like `arc_kmem_reap_soon()` is synchronous on FreeBSD! So, > >>>> this `delay()` looks very wrong. Am I right? > >> > >> Why is it wrong? > > One second pause after synchronous operation to wait it completion? > > No. To rate-throttle them. This gives UMA a second to get back into > minimally steady state after we ripped all caches from it. As I have > told, we do not want to drain caches constantly in a tight loop, we want > more or less steady state. And also (posible) additionaly delay arc_get_data_impl(). This is incorrectly throttling implementation.
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