From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-qk0-f199.google.com (mail-qk0-f199.google.com [209.85.220.199]) by kanga.kvack.org (Postfix) with ESMTP id 708ED6B0389 for ; Mon, 27 Feb 2017 15:29:09 -0500 (EST) Received: by mail-qk0-f199.google.com with SMTP id r90so148393481qki.0 for ; Mon, 27 Feb 2017 12:29:09 -0800 (PST) Received: from mail-yw0-x242.google.com (mail-yw0-x242.google.com. [2607:f8b0:4002:c05::242]) by mx.google.com with ESMTPS id d189si12718407qkf.177.2017.02.27.12.29.08 for (version=TLS1_2 cipher=ECDHE-RSA-AES128-GCM-SHA256 bits=128/128); Mon, 27 Feb 2017 12:29:08 -0800 (PST) Received: by mail-yw0-x242.google.com with SMTP id l138so2983588ywc.0 for ; Mon, 27 Feb 2017 12:29:08 -0800 (PST) Date: Mon, 27 Feb 2017 15:29:06 -0500 From: Tejun Heo Subject: Re: [PATCH v2 3/3] percpu: improve allocation success rate for non-GFP_KERNEL callers Message-ID: <20170227202906.GF8707@htj.duckdns.org> References: <201702260805.zhem8KFI%fengguang.wu@intel.com> <20170226043829.14270-1-tahsin@google.com> <20170227095258.GG14029@dhcp22.suse.cz> <20170227195126.GC8707@htj.duckdns.org> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: Sender: owner-linux-mm@kvack.org List-ID: To: Tahsin Erdogan Cc: Michal Hocko , Christoph Lameter , Andrew Morton , Chris Wilson , Andrey Ryabinin , Roman Pen , Joonas Lahtinen , zijun_hu , Joonsoo Kim , David Rientjes , linux-mm@kvack.org, linux-kernel@vger.kernel.org Hello, On Mon, Feb 27, 2017 at 12:27:08PM -0800, Tahsin Erdogan wrote: > A better example is the call path below: > > pcpu_alloc+0x68f/0x710 > __alloc_percpu_gfp+0xd/0x10 > __percpu_counter_init+0x55/0xc0 > cfq_pd_alloc+0x3b2/0x4e0 > blkg_alloc+0x187/0x230 > blkg_create+0x489/0x670 > blkg_lookup_create+0x9a/0x230 > blkg_conf_prep+0x1fb/0x240 > __cfqg_set_weight_device.isra.105+0x5c/0x180 > cfq_set_weight_on_dfl+0x69/0xc0 > cgroup_file_write+0x39/0x1c0 > kernfs_fop_write+0x13f/0x1d0 > __vfs_write+0x23/0x120 > vfs_write+0xc2/0x1f0 > SyS_write+0x44/0xb0 > entry_SYSCALL_64_fastpath+0x18/0xad > > A failure in this call path gives grief to tools which are trying to > configure io > weights. We see occasional failures happen here shortly after reboots even > when system is not under any memory pressure. Machines with a lot of cpus > are obviously more vulnerable. Ah, absolutely, that's a stupid failure but we should be able to fix that by making the blkg functions take gfp mask and allocate accordingly, right? It'll probably take preallocation tricks because of locking but should be doable. Thanks. -- tejun -- To unsubscribe, send a message with 'unsubscribe linux-mm' in the body to majordomo@kvack.org. For more info on Linux MM, see: http://www.linux-mm.org/ . Don't email: email@kvack.org