From mboxrd@z Thu Jan 1 00:00:00 1970 Received: from smtp.kernel.org (aws-us-west-2-korg-mail-1.web.codeaurora.org [10.30.226.201]) (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 D82AA226D02 for ; Fri, 19 Sep 2025 20:06:45 +0000 (UTC) Authentication-Results: smtp.subspace.kernel.org; arc=none smtp.client-ip=10.30.226.201 ARC-Seal:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758312406; cv=none; b=G+g+OYakXMsPeZ1Tm2qvVbuU9d/h1h1Di6117IahAB+LPQ71oMTJqdnkC/nayxKBOtAKmWp5ppPNRW25MMGOA3Fhv/SnkZSN3D1eQP4FYVE4SFzdAItDIAnngJwJlTegwIzwkbCL0ffzJpBV3mhUeb/IqDd8Bd+ns9pHhvKn8Rg= ARC-Message-Signature:i=1; a=rsa-sha256; d=subspace.kernel.org; s=arc-20240116; t=1758312406; c=relaxed/simple; bh=oU6IPcrhdCatbty9M1JygZaaWUYhUxIhORgdHeVOnGI=; h=Date:From:To:Cc:Subject:Message-Id:In-Reply-To:References: Mime-Version:Content-Type; b=epazwwNbDufdzcPigp9MfGPz/x9WSTo9SLjioSMlFbMy009l6Hpob2E58cEqC7M6ifRE7Oh17JVon2msxw2q8gsA5fyuen/Hcg6TxfJ4Lzm8/xcza2m2mMIP3Loir5XeA2YD/+WPhqXPfEaRATWGNZ2JJy8qM/oKa7OxC1mOCeE= ARC-Authentication-Results:i=1; smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b=wchAFv1v; arc=none smtp.client-ip=10.30.226.201 Authentication-Results: smtp.subspace.kernel.org; dkim=pass (1024-bit key) header.d=linux-foundation.org header.i=@linux-foundation.org header.b="wchAFv1v" Received: by smtp.kernel.org (Postfix) with ESMTPSA id 20FE7C4CEF0; Fri, 19 Sep 2025 20:06:45 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/simple; d=linux-foundation.org; s=korg; t=1758312405; bh=oU6IPcrhdCatbty9M1JygZaaWUYhUxIhORgdHeVOnGI=; h=Date:From:To:Cc:Subject:In-Reply-To:References:From; b=wchAFv1vt+vhyzhItwupGq5aAmioJFZOe/0Zmxv1rki1kUWHXg5byUVLtajCkTXqV FFhvI35l7xkd5V0xk5e922SIgSo1jHmwwuZhp3BL9Kong4YYq5baiutPIMUcptEuri KJMdlDmGad89OkoV8v1l5RhnXnTm0OAki1Uh29ac= Date: Fri, 19 Sep 2025 13:06:44 -0700 From: Andrew Morton To: Joshua Hahn Cc: Johannes Weiner , Chris Mason , Kiryl Shutsemau , "Liam R. Howlett" , Brendan Jackman , David Hildenbrand , Lorenzo Stoakes , Michal Hocko , Mike Rapoport , Suren Baghdasaryan , Vlastimil Babka , Zi Yan , linux-kernel@vger.kernel.org, linux-mm@kvack.org, kernel-team@meta.com Subject: Re: [PATCH 0/4] mm/page_alloc: Batch callers of free_pcppages_bulk Message-Id: <20250919130644.f3a4afdf0c2e51bbec59b6e0@linux-foundation.org> In-Reply-To: <20250919195223.1560636-1-joshua.hahnjy@gmail.com> References: <20250919195223.1560636-1-joshua.hahnjy@gmail.com> X-Mailer: Sylpheed 3.8.0beta1 (GTK+ 2.24.33; x86_64-pc-linux-gnu) Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit On Fri, 19 Sep 2025 12:52:18 -0700 Joshua Hahn wrote: > While testing workloads with high sustained memory pressure on large machines > (1TB memory, 316 CPUs), we saw an unexpectedly high number of softlockups. > Further investigation showed that the lock in free_pcppages_bulk was being held > for a long time, even being held while 2k+ pages were being freed [1]. What problems are caused by this, apart from a warning which can presumably be suppressed in some fashion? > This causes starvation in other processes for both the pcp and zone locks, > which can lead to softlockups that cause the system to stall [2]. [2] doesn't describe such stalls. > > ... > > In our fleet, we have seen that performing batched lock freeing has led to > significantly lower rates of softlockups, while incurring relatively small > regressions (relative to the workload and relative to the variation). "our" == Meta?