From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-io0-f199.google.com (mail-io0-f199.google.com [209.85.223.199]) by kanga.kvack.org (Postfix) with ESMTP id 46C2A6B0038 for ; Tue, 28 Nov 2017 18:41:14 -0500 (EST) Received: by mail-io0-f199.google.com with SMTP id p204so1290541iod.16 for ; Tue, 28 Nov 2017 15:41:14 -0800 (PST) Received: from mail-sor-f41.google.com (mail-sor-f41.google.com. [209.85.220.41]) by mx.google.com with SMTPS id q1sor412950itq.126.2017.11.28.15.41.13 for (Google Transport Security); Tue, 28 Nov 2017 15:41:13 -0800 (PST) MIME-Version: 1.0 In-Reply-To: References: <1511841842-3786-1-git-send-email-zhouzhouyi@gmail.com> From: Zhouyi Zhou Date: Wed, 29 Nov 2017 07:41:12 +0800 Message-ID: Subject: Re: [PATCH 1/1] kasan: fix livelock in qlist_move_cache Content-Type: text/plain; charset="UTF-8" Sender: owner-linux-mm@kvack.org List-ID: To: Dmitry Vyukov Cc: Andrey Ryabinin , Alexander Potapenko , kasan-dev , Linux-MM , "linux-kernel@vger.kernel.org" Hi, I will try to reestablish the environment, and design proof of concept of experiment. Cheers On Wed, Nov 29, 2017 at 1:57 AM, Dmitry Vyukov wrote: > On Tue, Nov 28, 2017 at 6:56 PM, Dmitry Vyukov wrote: >> On Tue, Nov 28, 2017 at 12:30 PM, Zhouyi Zhou wrote: >>> Hi, >>> By using perf top, qlist_move_cache occupies 100% cpu did really >>> happen in my environment yesterday, or I >>> won't notice the kasan code. >>> Currently I have difficulty to let it reappear because the frontend >>> guy modified some user mode code. >>> I can repeat again and again now is >>> kgdb_breakpoint () at kernel/debug/debug_core.c:1073 >>> 1073 wmb(); /* Sync point after breakpoint */ >>> (gdb) p quarantine_batch_size >>> $1 = 3601946 >>> And by instrument code, maximum >>> global_quarantine[quarantine_tail].bytes reached is 6618208. >> >> On second thought, size does not matter too much because there can be >> large objects. Quarantine always quantize by objects, we can't part of >> an object into one batch, and another part of the object into another >> object. But it's not a problem, because overhead per objects is O(1). >> We can push a single 4MB object and overflow target size by 4MB and >> that will be fine. >> Either way, 6MB is not terribly much too. Should take milliseconds to process. >> >> >> >> >>> I do think drain quarantine right in quarantine_put is a better >>> place to drain because cache_free is fine in >>> that context. I am willing do it if you think it is convenient :-) > > > Andrey, do you know of any problems with draining quarantine in push? > Do you have any objections? > > But it's still not completely clear to me what problem we are solving. -- 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