From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.subspace.kernel.org (Postfix) with ESMTPS id C5F9415A9 for ; Wed, 22 Mar 2023 08:38:49 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=infradead.org; s=bombadil.20210309; h=In-Reply-To:Content-Type:MIME-Version :References:Message-ID:Subject:Cc:To:From:Date:Sender:Reply-To: Content-Transfer-Encoding:Content-ID:Content-Description; bh=EG+7LordkRHpR5uhHeSEb0P0yx1Z21UB61C1gfuQScQ=; b=G5fV4nA74ELtZE4stXwQxO0Cva p3FAwG0MXYLbW+PkUQkxidtzaEPjR9p+Swt4S4DHwnhUt64TQcOLAZQvFwhTQoyKGa54oMNQoDVUO Q1UNSZqIagQwQ/YsxbwW4C63ttYszoKda4A1p3mZFJEYNIo7GGMqvCUB77gGqauOm9m93L5kMDA/1 pA7SGj3KI+brd/fLTRjFN007Jf2dA0wU0INnFIv7O47zT4qCu6X4zxe0NWGFHwbwZsmAoISpHqQjC kZoDCPzD5q/hh7VFatyPapdRMC5B0Iq1N3tcUnbgKdxbHnCvBe25f92251t4ghVCAOuJDy4a7fY/V +JeI2rLQ==; Received: from hch by bombadil.infradead.org with local (Exim 4.96 #2 (Red Hat Linux)) id 1petzW-00FDaS-0H; Wed, 22 Mar 2023 08:38:42 +0000 Date: Wed, 22 Mar 2023 01:38:42 -0700 From: Christoph Hellwig To: Josef Bacik Cc: Christopher Price , slyich@gmail.com, anand.jain@oracle.com, boris@bur.io, clm@fb.com, dsterba@suse.com, linux-btrfs@vger.kernel.org, regressions@leemhuis.info, regressions@lists.linux.dev Subject: Re: [6.2 regression][bisected]discard storm on idle since v6.1-rc8-59-g63a7cb130718 discard=async Message-ID: References: Precedence: bulk X-Mailing-List: regressions@lists.linux.dev List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: X-SRS-Rewrite: SMTP reverse-path rewritten from by bombadil.infradead.org. See http://www.infradead.org/rpr.html On Tue, Mar 21, 2023 at 05:26:49PM -0400, Josef Bacik wrote: > We got the defaults based on our testing with our workloads inside of > FB. Clearly this isn't representative of a normal desktop usage, but > we've also got a lot of workloads so figured if it made the whole > fleet happy it would probably be fine everywhere. > > That being said this is tunable for a reason, your workload seems to > generate a lot of free'd extents and discards. We can probably mess > with the async stuff to maybe pause discarding if there's no other > activity happening on the device at the moment, but tuning it to let > more discards through at a time is also completely valid. Thanks, FYI, discard performance differs a lot between different SSDs. It used to be pretty horrible for most devices early on, and then a certain hyperscaler started requiring decent performance for enterprise drives, so many of them are good now. A lot less so for the typical consumer drive, especially at the lower end of the spectrum. And that jut NVMe, the still shipping SATA SSDs are another different story. Not helped by the fact that we don't even support ranged discards for them in Linux.