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[129.97.60.193]) by smtp.gmail.com with ESMTPSA id l136sm16247itc.23.2019.05.20.09.42.14 (version=TLS1_2 cipher=ECDHE-RSA-CHACHA20-POLY1305 bits=256/256); Mon, 20 May 2019 09:42:14 -0700 (PDT) Sender: Mark Johnston Date: Mon, 20 May 2019 12:42:10 -0400 From: Mark Johnston To: Lev Serebryakov Cc: freebsd-fs@freebsd.org, freebsd-hackers@freebsd.org, Alexander Motin Subject: Re: Commit r345200 (new ARC reclamation threads) looks suspicious to me - second potential problem Message-ID: <20190520164202.GA2130@spy> References: <369cb1e9-f36a-a558-6941-23b9b811825a@FreeBSD.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <369cb1e9-f36a-a558-6941-23b9b811825a@FreeBSD.org> User-Agent: Mutt/1.11.4 (2019-03-13) X-Rspamd-Queue-Id: 9EE2B86F8C X-Spamd-Bar: ----- Authentication-Results: mx1.freebsd.org; dkim=pass header.d=gmail.com header.s=20161025 header.b=tIi4z9qU; spf=pass (mx1.freebsd.org: domain of markjdb@gmail.com designates 2607:f8b0:4864:20::12a as permitted sender) smtp.mailfrom=markjdb@gmail.com X-Spamd-Result: default: False [-5.49 / 15.00]; ARC_NA(0.00)[]; RCVD_VIA_SMTP_AUTH(0.00)[]; R_DKIM_ALLOW(-0.20)[gmail.com:s=20161025]; NEURAL_HAM_MEDIUM(-1.00)[-1.000,0]; FROM_HAS_DN(0.00)[]; RCPT_COUNT_THREE(0.00)[4]; R_SPF_ALLOW(-0.20)[+ip6:2607:f8b0:4000::/36]; TO_MATCH_ENVRCPT_ALL(0.00)[]; MIME_GOOD(-0.10)[text/plain]; RCVD_TLS_LAST(0.00)[]; DMARC_NA(0.00)[freebsd.org]; TO_DN_SOME(0.00)[]; NEURAL_HAM_LONG(-1.00)[-1.000,0]; RCVD_COUNT_THREE(0.00)[3]; IP_SCORE(-2.79)[ip: (-8.38), ipnet: 2607:f8b0::/32(-3.25), asn: 15169(-2.26), country: US(-0.06)]; DKIM_TRACE(0.00)[gmail.com:+]; MX_GOOD(-0.01)[cached: alt3.gmail-smtp-in.l.google.com]; RCVD_IN_DNSWL_NONE(0.00)[a.2.1.0.0.0.0.0.0.0.0.0.0.0.0.0.0.2.0.0.4.6.8.4.0.b.8.f.7.0.6.2.list.dnswl.org : 127.0.5.0]; NEURAL_HAM_SHORT(-0.98)[-0.985,0]; FORGED_SENDER(0.30)[markj@freebsd.org,markjdb@gmail.com]; MIME_TRACE(0.00)[0:+]; MID_RHS_NOT_FQDN(0.50)[]; FREEMAIL_ENVFROM(0.00)[gmail.com]; ASN(0.00)[asn:15169, ipnet:2607:f8b0::/32, country:US]; FROM_NEQ_ENVFROM(0.00)[markj@freebsd.org,markjdb@gmail.com] X-BeenThere: freebsd-fs@freebsd.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Filesystems List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 20 May 2019 16:42:19 -0000 On Mon, May 20, 2019 at 07:05:07PM +0300, Lev Serebryakov wrote: > > I'm looking at last commit to > 'sys/cddl/contrib/opensolaris/uts/common/fs/zfs/arc.c' (r345200) and > have another question. > > Here are such code: > > 4960 /* > 4961 * Kick off asynchronous kmem_reap()'s of all our caches. > 4962 */ > 4963 arc_kmem_reap_soon(); > 4964 > 4965 /* > 4966 * Wait at least arc_kmem_cache_reap_retry_ms between > 4967 * arc_kmem_reap_soon() calls. Without this check it is > possible to > 4968 * end up in a situation where we spend lots of time reaping > 4969 * caches, while we're near arc_c_min. Waiting here also > gives the > 4970 * subsequent free memory check a chance of finding that the > 4971 * asynchronous reap has already freed enough memory, and > we don't > 4972 * need to call arc_reduce_target_size(). > 4973 */ > 4974 delay((hz * arc_kmem_cache_reap_retry_ms + 999) / 1000); > 4975 > > But looks like `arc_kmem_reap_soon()` is synchronous on FreeBSD! So, > this `delay()` looks very wrong. Am I right? > > Looks like it should be `#ifdef illumos`. See also r338142, which I believe was reverted by the update.